呼吸筋不全の基礎的研究:低濃度酸素ガス吸入の影響

呼吸筋不全の基礎的研究:低濃度酸素ガス吸入の影

響

著者

進藤 千代彦

司mNu用甘

潮間際勘.

-._ .･11■ l一一rll･

目撃3

呼吸筋不全の基礎的研究:低濃度酸素ガス吸入の影響

課題番号  09670596

平成9年度∼平成1 0年度科学研究費補助金(基盤研究(C)(2))

研究成果報告書

平成11年 3月

研究代表者  進藤千代彦

(東北大学医療技術短期大学部)

00010176034 L l

研究組織

研究代表者:進藤千代彦 (東北大学医療技術短期大学部)

研究経費

平成 9年度       160万円 平成1 0年度         60万円 計       220万円

研究発表

(1)学会誌等 (①進藤千代彦:呼吸筋疲労とは､ (肺機能検査法と評価) ､呼

吸､ 16 (1)､ 39-44､ 1997; ②進藤千代彦:吸入補助システム の効率と効果､アレルギーの領域､ 4 (8)､ 46-51､ 1997; ③C.

Shindoh, D. Wu, Y. Ohuchi, H. Kurosawa, Y. Kikuchi, W. Hida, K.

Shirato: Effects of L-NAME and L-arginine on diaphmgm COntraCtion in a septicanimalmodel. Comp. Biochem. Physio1., 119A (i), 219-224,

1998 ; @A. Taneda, C. Shindoh, Y. Ohuchi, K. Shirato: Protective

effects of interleukin-10 0n diaphragm muSCleina septic anhlalmodel.

TohokuJ. Exp. Med. 180 (1),45-54, 1998; @C. Shindoh, D. Katayose,

K･ Shirato: Effects of interferonrα and r on diaphragm muscleinrats. Bu皿. Coll. Med. S°i.Tohoku Univ. 8 (1), 3ト42, 1999)

(2旧頭発表 (①○進藤千代彦､片寄大､呉徳男､白土邦男:低濃度酸素吸入

による横隔膜筋収縮力の変化｡ 1 997､ 4 第37回日本胸部疾患学会総会

(*&) ; @OC. Shindoh, D. Katayose, D.Wu,and K. Shirato: Effects

of Continuous Hypoxic Gas Inhalation on Diaphmgm Muscle Contraction

in Rats.American Thoracic Society (SanFrancisco), 1997 (5) ; ③OC.

Shindoh, M. Ichinose, G. Tamura, T. Takishima, and K. Shirato: Effects

of anti-TNF-α antibodyinhalation on endotoxininduced diaphragm

dysfunction. The llth Congress.'Intemational Society for Aerosolsin

Medicine.. (Sendai), 1997(9) ; ④○進藤千代彦､片寄大､白土邦男.･ Interleukin-8の横隔膜筋収締カへの影響｡ 1 9 9 8､ 3 第3 8回日本呼吸

器学会総会(熊本) ; ⑤OC. Shindoh, D. Katayose, and K. Shirato:

Effects of lnterleukinr8 0n Diaphram Muscle Contractionin Rats.

AmericanThoracic Society (Chicago) , 1998 (4))

(1)実験装置の作製について･･･本研究の実験装置は今回設備晶に申請している

サーマル式ペンオシログラフの購入とともに､ organbathを作製し､測定系を

完成させた｡この装置をもちいて､課題である低酸素ガス吸入による横隔膜筋

への影響に関する実験を実掩した｡

(2)横隔膜筋収縮特性､筋線経の変化について-FIO2 1 0 %の低濃度酸素ガス

をラットの飼育チャンバーに持続的に流入させ､ 3日､ 1､ 2､ 3週間後に､

横隔膜筋筋小片を作製し収縮特性を評価した｡ 1 ､ 2週後に張力ー周波数曲線

が最も低下し､収縮はslow化し､繰り返し刺激に対して疲労抵抗性に変化し

た｡ 3週後にはいずれもコントロール値に戻る傾向を示し､低酸素状態での適

応反応と思われる反応が見られた｡筋線経の変化はATPase染色にて評価した｡

_.3 El後に単位面積あたりの遅筋線錐の速筋線経に対する比率が最も多くなり､

遅筋線維優位に変化したが､次第にこの比率はコントロール値に復帰した｡

(3) Hemo oxygenase (HO)､ NO synthase (NOB)発現の検討-H0-1は､第1

日目に有為の発現がみとめたが､その後は減少した｡ HOはス一汁-オキサイ

ドに対して防御的な作用を持つ｡又iNOSは第1日目に低下したが､その後増

加したのに対して､ eNOSは全期間にわたって増加していた｡

(4)以上の結果から､低酸素負荷の早期にス-/トオキサイドを防御するHO_

1が増加､ iNOSは減少し､これらが防御機構として働いていることが判明し

た｡その後継続的なeNOSが見られ適応反応に関与している可能性が推察され

た｡横隔膜筋はその発生張力の減少が呼吸筋不全に関係するが､本研究により､

低酸素状態における横隔膜筋収縮力や筋線経の変化の機序として､ H0-1,

iNOS, eNOS発現とが密接な関係にあることが結論づけられた｡

参考文献

(1)当該論文 (2)発表論文その1

(3)発表論文その2

(4)発表論文その3

Effects of Continuous Hypoxia on Diaphragm Muscle Contraction

and Fibers in Rats

by

CHIYOHIKO SHINDOH

Department of Medical Teclmology,

College of Medical Sciences Tohoku Umiverslty,

2- 1 Seiry0-machi, Aoba-ku, Sendai980-8575

Abstract

SinCe hypoxemia is frequendy observed in padents withrespiratory diseases, we

examined whether continuous hypoxic gas inhaladon affbctsthe diaphragm contractile

properties in rat･ Hypoxic gas (FIO2 ≡ 0･ 10) was produced by two reversely connected oxygen

emichersand was continuously fedintothe breeding chamber･ At 3, 7, 14,and 21 days of

hypoxia (n = 6, respectively), we dissectedthe diaphragm muscle under lightanesthesia, made

muscle strips, and measured force-frequency curves, twitch kineticsand由血gability in vitro,

and muscle fiber compositionsby ATPase staining･ At 7 days of hypoxia,the fo代浩一fFequenCy

curves decreased to 1.53 ± 0.07 kg/cm2, bothContractiontime and half Felaxadontime

elongated to 85 ± 5･0and 93 ± 3･l msec, respectively,and fatigability increased to 18 ± 1.3%.

However, at 21 days,these parameters retumed to nearcontrol values (1.75 ± 0.07 kg/cm2･ 67

± l･8 msec, 76 ± 4･7 msec,and I5 ± 0･9 %, respectively). At 3 days, typeⅠ (slow twitch)

muscle fiber increased to 40.3 ± 2.2 %, and type II (fast twitch) decreased to 59.7 ± 2.2 %; at

21 days, however,these valu飴also retumed (32.1 ± I.9 %, 67.9 ± 1.9 %, respectively) to

nearcontrol values･ Fromthese results･ We concludethatthe diaphragm muscle inthe early

phase of hypoxia decreases force-&equency ctlrVeSand slows contractionwithCorresponding

fiber changes; however,these changes are reversedand a non-hypoxIC State Simnartothe

control is seen at 21 days･ It is suggestedthatthe diaphragm muscle hasthe ability to adapt to

Introduction

lt is well knownthat hypoxia induces a decrew of skeletalmuscle tensionand

enhances muscle fatigue (14)･ J･ Jardim etal･ reportedthatthe effect of low oxygen breathing

(nO2 = 0･13) on inspiratory muscle fatigue resulted in a shorter endurance time, a faster ratein

the shift of the electromyographic power spectrum,and a greater rate ofincreaseinblood lactate

concentrations during inspiratory resisdve breathinginnormalsubjects (13). In addition,

exhausdve exercise during hypoxia (no2 = 0. 12) caused marked hyperventilationand reduced

arterial02 COntent; glycogen fellinthe plantariS (20% of control)and inthe diaphragm (58%),

the sparing effect of which is due primarily toglucose-6-phosphataseinhibidon ofglycogen

phosphorylase inthe diaphragm muscle (8). Furthermore, S. A. Esau reportedthat hypercapnlC aCidosis had a greater negativeinotropic effect onthe diaphragm musclethandid

hypoxiaalone,and madethe muscle more susceptible to fatigue in vitno (7). Becausethe

impaiJed enduranceperformance of muscles during physicalexercise is a well-recognized

response to conditions of acute normobaric or hypobaric hypoxia, it is considered to tN3 Closely

related tothe reductioninmaximalaerobic power due to arterialhypoxemia (9).

However,these findings were concemed withreladvely acute hypoxia of short

duration,therefore･the e飴cts of longer continuous hypoxia onthe diaphragm contractile

properties have not been well elucidated･ Moreover, to ourknowledge, diaphragm muscle fiber

composidon has not been examined under either acute or long hypoxia･ Inthe present study,

therefore･ we examined whetherthe diaphragm muscle contractile propertleS andthe

composidonsof tyFX: Ⅰ (Slow-twitch)and typeII (fast-twitch) muscle fibers change during 21

days of hypoxia.

Methods and Materials

A血mal DreDaradon

Experiments wereperformed using 30 Wistar rats weighing 250-320 g (Chades River

Japan, Kanagawa, Japan)･ The control group (n = 6) was loadedwithambient atmospheric gas

阿02 = 0･21),andthe hypoxic gas inhaladon group (totaln = 24) was loadedwitha hypoxic gas (nO2 ≡ 0･10)･ The hypoxic gas was produced by fiedingthe emiust gasfromthe丘rst

oxygen emicher intotheinlet of the second oxygen emicher;the oxygen鉦action of the exhaust

gasfromthe second oxygen emicher was approximately lO% (FIO2 = 0.10). ne hypoxic gas

was cominuously fedinto breeding cages coveredwithtranslucent plastic sheets. The animals

of each group were caged, isolated forthe duration of the experlment, and maintained on a

12:12lhlight-dark cycle atambient temperature (23 - 25oC). We performed two kinds of

measurement:のdiaphragm muscle contracdle properdes were measured in vitro inthe control

group (n = 6)andinthe hypoxic gas inhalation group at 3, 7, 14,and 21 days (n = 6 each), OI) muscle samples takenfromthe control groupandthe hypoxic gas inhalation group at 3, 7, 21

days were studied histologiCally by ATPase staining. Written approvalwas obtainedfromthe

TohoknUniversity AdmalFacility.

Diat)hraEm mtlSCle contractile measurements

The measurements of di叩hragm muscle contractility wereperformed as previously

reported (19)･ Briefly, two muscle strips (34 mmwide) were dissected fromtherightand le氏

hemidiq)hragm under diethyl etheranesthesia and mountedinsqparate organ baths containing

Krebs-Henseleit solution oxygenatedwitha 95% Q2 - 5% C 02 gas mixture (23.5 ± 0.5oC, pH

7･40 ± 0･05)I The composition of the aerated K陀bs-Henseleit solutioninmEq/L was as

follows: Na', 153･8; K', 5･0; Ca2', 5･0; Mg2', 2･0; C1-, 145.0; HCO31, 15.0; HPO42-, 1.9;

SO42-, 2･0; glucose･ 1 10 mg%; 10 pM d-tubocurarine; regularcrystalline zinc insulin, 50 U化.

Bothmuscle strips were simultaneously sdmulatedwithsupramaximalctmnts (i.e., 1.2 to 1.5

timesthe currmt requiJd to ehcit･maximaltwitch tension, 200-250 mA, pulses of 0.2 msec

duration) by a constant ctmt stimulus isolationmit (SS-302J, Nihon Kohden) driven by a

stimulator (SENl3201, Nihon Kohden)･ ne曲ited tensions weJT measured by aforce

transduceq (UL-100GR, Minet- Co･)･ The lengthof each muscle strip was changed by

movingthe position of the force transducerwithamicrometer-C孤trOued rackand pimion gear

(accuracy of dhplacernent, 0･05 mm),and measuredwithamicrometerinclose proximity to

the muscle･ The optimallengthofthe muscle (b) was de血ed asthe muscle lengthat which

twitch tension development was maximal･and thisLewas maintained inthe following

measurements.

The diaphragm force-frequency relationship was assessed by sequentially stimulating

muscles at l･ 10･ 20･ 30･ 50･ 70･and 100 Hz･ Each stimulus train was applied for

approximately 1 see,and adjaant tmins were applied atintervals of approximately 10 see. The

tensions of bothmuscle s仕ips werei r,eCOrded by a hot-pe-ecorder (RECTI-HORIZ-8K,

San-ei, Tokyo)･ ne force-frequency curves obtained fromthe groups studied were displayed as

elicited tensions O'g/cm2) onthe Y-axisand sdmula血g frequencies onthe X-axis.

Twitch contraction was elicited by single pulse stimulation (0.2 msec),andthe trace of

the twitch contracdon was recorded at highspeed (10 cm/see). The twitch kinetics were

assessed by (I) twitch tension (peak tension of twitch contracdon, kg/cm2), (q contractiontime

(thetime required to develop peak tension, msec), and (Ill) halhelaxationtime (thetime

required for peak tension to向山by 50%, msec) during a single muscle contraction.

Muscle fatigability wasthen assessed by examiningthe rate of鮎l of tension over 5 min

of rhythmic contraction･ Rhythmic contraction was induced by applying tmins of 20 Hz stimuli

(train duration, 0･33 S; rest duration, 0.66 S; tmin:rest ratios, l:2) at a 60 tmin/min rate. Muscle

fatigability was expressed as apeICentage Ofthe Analremaining tension (%) fromthe imitial

tension･ A飴r completion of this protocol,the muscle strip was FemOVedfromthe bathand

weighed.

Then, muscle strips were adjusted to Loand rlXed withpins on a cork plate. Samples

were immediately emhBdded in mounting medium (OCT compound, Miles, Ekhart, IN),

immersedinisopentane Wako Pure Chemicallmdustries Ltd., Osaka, JapaJl)that had been

cooledinliquid nitrogen,and storedina refdgerator (180oC) to awaitfurtheranalysis.

Adenosine tri_Dhosphatase (ATPase) stain

Myofibri皿aradenosine triphosphatase (ATPase) staining of the diaphragm was

performed according tothe method of Dubowitz and Brooke (5). Diaphragm sampletissues

were sectioned to 10 pm witha cryostat (BRIGHT Instrument, Humingdon, UK) kept at

-20oC･ Onthe basis of their staiming reactions for myofibriuarATPase, after akdine

preincubation (pH IO･4), musclefibers were classified as either type I or type A Unstained

as type II (bothhighoxidative fast-twitchand low oxidative fast-twitch). Fiber crossISeCtional

areas were _measured by digitizing witha computerized image-processing system (PIAS Co.,

Tokyo, Japan)･ The aJea Was determined fromthe number of pixels withinthe oudined

borders, witheach pixel having a widthof O･125 mm･ FihBr type prOPOrtionsand

cross-secdonalaFeaS (CSA) Were determined h)m a sample of 350-400fibers using severalsections

of each muscle･ Fiber CSA (X20) were determinedfromthe number of pixels withinthe

outlined borders, witheach pixel having all area Of O･676 pm2 at x20 magnification.

DataAnalysis

ne ship muscle cross-sectionalaJm Was Calculated by dividing muscle mass bythe

product of s也p muscle lengthaJld muscle density (1.06 g/cm3), aJld tension was calculated as force permit -a O'g/cm2) (4)･ The mean values for each frequencyinforce一触quency

curves, twitch kineticsand fadgability were compaJ℃d by Student's i -test.All data ale

presented as mews ± SE･ Data witha p value of lessthan0･05 were considered statisdcany

significant.

Results

Changes of muscle conBactile DrODerdes

Figure 1 showsthe mean force-beqtwncy ctmes of the control groupandthoseinduced

by hypoxia血)m 3 to 21 days･Asfor comparwons of the tensions at corresponding

frequencies,the tensionsinlowertranges (land 10 Hz) at 7 and 14 days were sigmifiCandy

increased, whilethose in higher ranges C70 to loo Hz) Were signibandy decreased fromthose

of the control force-触quency curve († p < 0･Ol, 辛 p < 0.001, respectively).触changes were caused by leftward shift of force-frequency curves duringthe early phase of hypoxia (i.e.,

3 to 7 days)･ At 21 days,the tensionsinthe higher ranges had recovered to levelsintennediate

btween 7 days andthe control,andthe tensionsinthe lower ranges had decreased to near

control values.

Figure 2 summarizesthe me弧Changes of twitch kineticsand鮎gability inthe control

inhalation maximally increased at 3 days ∼, < 0.001),then decreased by 21 days,althougheach

twitch tension was sigmificantly largerthaJlthe control value b < 0.01).As for contraction

times (B),they were maximally elongated by 7 days,then decreased tothe control level by day

21 during hypoxic gas inhalation; each contractiontime was sigmificandy longerthanthe control

value b < 0･001)I Withregard to halfrelaxationtime (C), it wasalso maximally elongated at 7

days b < 0･001),then decreased by day 21 (〟 < 0.05) during hypoxic gas inhalation. The

observedincreases of bothcontraction dmeand half relaxationtime at 7 days m飽nthatthe

diaphragm muscle contracted more slowlythanthe control,theMetumed tothe control level.

Conceming fatigability P), it was sigmificantlyincreased at 7and 14 days during hypoxic gas

inhaladon (bothp < 0･01), whilethere was no significant chaJlge at 3and 21 days. ne

increase of fadgability meanSthatthe diaphragm muscle became more fatigue resistantthanin

the control at 7and 14 days,then retumed tothe control level.

Changes of mt"3Cle Glh3r COmPOSidon

Figure 3 Shows typicalphotographs of myo丘bri11arATPase staiming at此he pH of

control (A), 3 days (B), 7 days (C), and 21 days (D) during hypoxia. Inthe alkaline pH,the

unstained and stained fibersindicate typeI (slow-twitch) aJldtype II (fast-twitch) muscle fibers.

At 3 days (B)and 7 days (C), becausethe number ofunstained muscle fibers increased

comparedwiththe numtx:rinthe control, it seemsthatthe white azea increasedandthe black

area decreased, inthe photograph.

Figure 4 showsthe meannumtxrs (percentage) of type I and typeII muscle丘berinthe

controland at 3, 7and 21 days during hypoxia. Thepercentage of typeⅠ (slow-twitch) muscle

fiber increased (40･3 ± 2.2%,p < 0.001) significantly付om that of the control (22.4 ± 1.1%),

then decreased at 7and 21 days (36･8 ± I.6%, p < 0.001; 32.1 ± 1.9%, p < 0.01,

respectively)･ Reciprocalchanges inthepercentages of typeⅡ were observed.

Figure 5 showsthe m飽n Changes of cross-sectionalareas of typeI and typeII inthe

controland 3, 7and 21 days during hypoxia･ The cross-sectionalaJm Of typeI muscle丘bers

oftypeII muscle fibers significandy increased at 3and 7 days b < 0.00l), and at 21 days Ql <

0.01)舟omthat of the control.

Discussion

Inthe present study, continuous hypoxia (FIO2 =- 0.10) induced diaphragm muscle

deterioradon and a leftward shift of the force-frequency curves,anelongation of contraction

and half pelaxationtimes, aJld fatigue resistance accompaJlied bytheincrements of type I

(slow-twitch) muscle fibers at 7 aJld 14 days･ However, at 21 days of hypoxia,theforce一触quency

curves, twitch kinedcsand muscle fiber composition Fetumed toward control levels. These

results suggestthatthe diaphragm muscle tmomes to slow-twitch muscle fiber dominant

muscleinthe early phase of cominuous hypoxia,andthen showsanadapdve response tothe

hypoxia by regalnlng nearly normalContractile properties as a result of a retum to normal

muscle fiber composition.

Studies of the diaphragm during lnsPlration of elevated O2丘actions have showman

increased resistaJICe tO fatigueand changesinventi1atory muscle recmitment auowing enhanced

performance, measured asincreased endurancetime (16). Conversely, moderate hypoxia, induced byinsplration of 13% 02, eXaarbated inspiratory muscle鮎gue as evidenced by

decreased endurancetimeand earlier shifts inthe electromyogramfrequency spectrum (13).

Three explanationsare suggested as to why hypoxia may Increase diaphragm fatigue during

intense whole body endurance exercise: (I) increased work bythe diaphragm, (II) decreased 02 transport tothe diaphragm,and (m)theinfluence of circula血g metabolites from locomotor

muscles working at a higher intensityin hypoxia (2). However, B. T.AmeFedes etal. reported

that鮎gue of the inspiratory muscles of nomalhuman subjects breathing 2 I % 02 (normoxia),

13% 02 (hypoxia), or l00% 02 (hyperoxia) who performed repeated maximalinSpiratory

maneuvers onanisoflow system did not show sigmificamt di飴rencesamongthethree

inspiration conditions (1)･ J･ Yan°s etal･ examined whether respiratory muscle fatigue plays a

role in resplratOry aLreSt using a dog model･ They reportedthat such fatigue may not be a major factorinresplratOryarreSt aSS∝iated widl inspiratory loadingand hypoxia, and suggested that

onthe relationship of muscle fatigueand moderate hypoxia have been inconsistent,andthatthe

diaphragm m_uscle, especidlyinhumanexperiments, shows resistance to muscle fatigue･

Onthe other hand, severalpotemialmechanisms or sites of failu托may aCCOuntforthe

hypoxic depression･ Inthe adult diaphragm, hypoxia rapidly inhibits nerve conduction (12)

and presynaptic transmitter release ( I 5)･ Complementalstudies have demonstratedthat hypoxia

depresses respiratory and nonrespiratory skeletalmuscle as well as cardiac muscle contracdlity (17, 21)･ Onthe postsynaptic side, hypoxia causes a depolad2ation of resting membrane

potential(20)and enhancement of mimiattm end-plate potemialfrequency (15, 12). A. R.

Bazzyreportedthat neuromusculartranSmission inthe newbom diaphragm is more resistint tO

the effects of hypoxiathanthe older diaphragm aJldthatthe predominant effect of hypoxia is

peripheralinthe diaphragm muscle fibers, whereas inthe older diaphragmthe effect is before

or atthe neuromuscularjunction (3)･Althoughthese previous studies con従ming hypoxia

focused on neuromusculartransmissionand resdng membrane potentialof diaphragm muscle,

it is possiblethatthese chaJlgeS Of nerve conduction or cell membrane may triggerthe changes

intheir fitx:r compositions.

In continuous hypoxia,aninteresting finding isthatthe diaphragm muscle inducedan

inc托ment inthe numb:r of type I (slow-twitch) muscle fibers. Because type I (slow-twitch)

muscle fiber is more fatigue resist肌tthan typeII (LTast-twitch) muscle fihBrS (4), it canbe

concludedthatthe changes of contractile properties were caused bythe histologiCalchangesin muscle fibers･ In a previous study, we reported a transientincrement of typeI (slow-twitch)

muscle fibers in a denervated diaphragm (18).Althoughthereare many differences inthe

expermentalsetups forinvestigating hypoxia and denervation, it has hBen generauy Observed

thatthe contractile properdesintypeI dominant muscle show a decreaseand leftward shift of

force-frequency curves･anincFeaSe Of contractiontime and half relaxationtime, aJld changesin

fatigue resistaJICe･ It is clearthatthe numtkr oftypeI dominant muscle fibers increases due to

hypoxia, because it occursinthe early phase of hypoxia･ However,the mechanisms resul血g

inthese muscle fiber changesinduced by continuous hypoxla are Still unclear,and further

Sincethe preiient Study wasperformed at sea level (i.e., normobaric hypoxia), it is of

panicularin_terest to refer to experlmentS COnducted at higheraltitudes. S. H. Gamer et al.

studiedthe force of the ankle dorsiflexors during a 40-day simulated ascent of Mt. Everestina

hypobaric chamber; bothelectriCally acdvatedand maximalvoluntary contractions were

employed,and it was foundthat chronicaltitude exposure did not appearto affectthe maximal

muscle force-generating capacity, but did have a mud effect onthe susceptibuity to fadgue

duringthe exercise protocols. 1mey concludedthatthe centralmotor drive becomes more

precarious at higheraltitudesand is associatedwithincreased muscle鮎gue at low excitation

frequencies;the latter isthe result,impart, of chronic hypoxia and occursinthe muscle fih3r

interior because no impaimentinneuromuscular transmission could h: demonstrated (1 I). C.

S･ Fulco etal･ reporhBdthat maximalvoluntary contracdonsofthe rested adductor pollicis

muscleare not impaired during or after acute (1 day) and chromiC (13 days) exerdon at high

aldtude (4,300mm) (10)･ It is suggestedthat our results of a leftward shi氏offorce-frequency

curves aJ℃ COmPadble withmaintained maximalContractions at highaltitudesandthat our

results on adaptation after transient changes may explain why severalbase camps are employed

when mountain climtx:rs attempt to reachthe summit.

In conclusion,the diaphragm muscle under continuous hypoxla Shows transient

changesinContracti1e propertleS Withchangesinmuscle Eih3r COmPOSition･ The underlying

mechanisms of these findings are unknown, butthe observed phenomenon may be triggered by hypoxia resulting ln a Changeinthe composition of the diaphragm muscle fibrsinthe early phase,witha rettlm tOthe control level inthe late phase. If temed adaptation to continuous

hypoxia, such adaptadon of the diaphragm muscle may occurinthe patients withchronic

hypoxia, for example, chromic obstrucdve pulmonary disease (COPD), fibrosing lung disease

(FLD), etc. Therefore, it is suggestedthat patients who surer LTrom COPD or FLD can tolerate chronic hypoxiafor many years due to such adaptation.

Acknowledgments

The?uthorwishes tothank Thomas Mandevi1lefor his review of the Englishinthis

paper･ This study was supported by a grant舟om The Ministry of Education, Science, Sports and Culture (No. 09670596) of Japan.

RererenceS

l･ Am早redes, B･ T･, aJld T･ L Clanton･ Hyperoxia and moderate hypoxia fail to affect

inspiratory muscle fatigue in humanS･ J･ Appl･ Physiol. 66: 894-900, 1989.

2･ Babcock, M･ A･, B･ D･ Johnson, D･ F･ Pegelow, 0･ E･ Suman, D. Griffin,and J. A.

Dempsey･ Hypoxic effects on exercise-induced diaphragmatic fatigueinnormalhealthy

humams. ). Appl. Physiol. 78: 82-92, 1995.

3･ -Bazzy･ A･ R･ Effect of hypoxia on neuromusculartransmission inthe developing

diaphragm. ). 4押l. Physiol. 76: 708-13, 1994.

4･ Close･ R･ I･ Dynamic properties ofmammalianskeletalmuscles･ Physiol･ Rev. 52:

129-197, 1972.

5･ Dubowitz, V･,and M. H. Brooke. HistologiCalaJld histochemicalstains and reactions.

h: Muscle Biopq･･ A Modern ALPnaCh, edited by V. Dubowitzand M. H. Brooke. London-Philadelphia-Toronto: W･B･ Sounders Company Ltd, 1973, p･ 20-33･

6･ Eastwood･ P･ R･, D･ R･ H山man,and K･ E･ Finucane･ Ventilatory responses to

insplratOrythreshold loadingand role of muscle Eatigueintask鮎lure･ J･ Appl･ Physiol･ 76:

185-95, 1994.

7･ Esau･ S･ A･ Hypoxic･ hypercapnlC aCidosis decreases tensionand increases fatiguein

hamster diaphragm muscle in viEro･ A仇Rev･ Respir･ Dis･ 139: 1410-7, 1989.

8･ Fregosi, R･ F･, and J･ A･ Dempsey･ Effects of exercise in normoxiaand acute hypoxia

9･ Fulco, C･ S･,and A･ Cymerman･ HumanperformaJICeand acute hypoxia･ In: Hu〝∽n

Peqornwce Physiok'gy and EnvirmmenhZl Medicine at TTewestru Extremes, edited by K. B.

Pandolf･ M･ N･ Sawkaand R･ R･ Gonzalez･ Indianapolis, IN: Benchmark, 1988, p･ 467-495.

10･ Fulco･ C･ S･, A･ CymermaJl, S･ R･ Muza, P. B. Rock, K. B. Pandolf,and S. F. Lewis･ Adductor pollicis muscle Lhtigue during acuteand chromiCaltitude exposureand retum

to sea level. ). 4押l. Physiol. 77: 179-83, 1994.

Ill -Gamer･ S･ H･･ J･ R･ Sutton･ R･ L nurse, A･ J･ McComas, A･ Cymerman,and C. S.

Houston･ Operation Everest II: netwomuscularperformaJICe under conditions of extreme

simulatedaltitude. ). 4LPl. Physiol. 68: 1 167-72, 1990.

12･ Hubbard･ J･ I･,and Y･ Loymng･ The effects of hypoxia on neuromusculartransmission

in a mammalianpreparation･ J･ Physiol. 185: 205-223, 1966.

13･ Jardim, J･, G･ Parkas, C･ Prefaut, D･ Thomas, P. T. Macklem,and C. Roussos. The

failing insplratOry muscles under normoxicand hypoxIC COnditions･ Atn･ Rev･ Respir･ Dis.

124: 274-9, 1981.

14･ Eing, C･ E･, S･ L Dodd,and S･ M･ Cain･ Muscle 02 deficitdming hypoxiaand two

levels of 02 demand･ J･ ALPL･ Physiol. 62: 1384-1391, 1987.

15･ Nishimura, M･ Factors influenclnganincrease in spontaneous transmitter release by

hypoxia atthe mouse neuromuscularjunction. ). Physiol. 372: 303-313, 1986.

16･ Pardy･ R･ L･･ and P･ T･ P･ Bye･ Diaphragmatic fatigue in normoxiaand hyperoxia. J.

17･ Saiomone, R･ J･,and E･ R･ Lunteren･ Effects of hypoxlaand hypercapnla On

gemiohyoid contracti1ity and endurance･ J･ Awl･ Physiol. 7 1 : 70917 15, 1991.

18･ Shindoh, C･, W･ Hida, H･ Kurosawa, S. Ebihara, Y. Eikuchi, T. Takishima,and K.

Shirato･ Effects of umilateralphremic nerve denervation on diaphragm contractilityin rat.

Tohoku J. Exp. Med 173: 2911302, 1994.

19･ Shindoh, C･, W･ Hida, Y･ Ohkawara, K. Yamauchi, I. Ohno, T. Takishima,and K.

Shirato･ TNF-α mRNA expression in diaphragm muscle after endotoxin admimistration. Atn J.

Respir. CT･it. Care. Med 152: 1690-1696, 1995.

20･ Vyskocil, F･･ F･ D･ Gregori0, and A･ Gorio･ The fa血tating effect of gangliosides on

the electrogemic Pal/K') pump and onthe resistance of the membrane potemialto hypoxiain

neuromuscularpreparation. PPugers Arch. 403: 1-6, 1985.

21. Watchko, J. F., W. A. LaFramboise, T. A. Standaert,and D. E. Woodrum.

Diaphragmatic function during hypoxemia: neonataland developmentalaspects･ J･ Appl･

Physiol. 60: 1599-1604, 1986.

22･ YaJIOS･ J･･ M･ d･ Keamy, L･Leisk, J･ B･ Hall, K･ R･ Walley,andL. D. Wood. ne

mechanism of resplratOry arrest in irISPiratory loadingand hypoxemia･ Atn･ Rev･ Respir･ Dis･

Figure legends

Fig･ 1 Force frquency curves of controland hypoxia groups at 3, 7, 14and 21 days･ Symbolsindicate sigmificant differences atgiven bequencies compared withControl (* p <

0.05, † p<0.01, 辛 p<0.001).

Fig･ 2 M飽n Changes of twitch tensions (A), Contractiontime (B), half relaxation血e (C),

and鮎gability (D)舟omthe diaphragm ofcontroland hypoxia groups at 3, 7, 14 and 21 days.

Symbols indicate significant differences comparedwithcontrol diaphragm (* p < 0.05, † p <

0.01_,.辛 p < 0.001).

Fig･ 3 Typicalphotographs of control group (A),and hypoxia group at 3 days (B), at 7 days

(C),and at 21 days (D). Magnification is x200.

Fig･ 4 Changes of numbers (percentage) of type I aJld typeII muscle fibers. Symbols

indicate sigmificant differences compared withcontrol diaphragm (千 p < 0.01, 辛 p < 0.00l).

Fig･ 5 Changes ofcrossISeCtionalareaS Of type 一and type Il muscle fibers･ Symbolsindicate

1.  0.

0

5

0 102030  50  70   100

Frequency (Hz)

-▲ ○ 岩 島 雷 苦 8 ControI  3day8  7dayB  ]4day8 2]daye Fig-2

Fatjgability (%)

･,A    -▲    N ⊂〉    Ul   ⊂〉   Ul   ⊂〉 C虫一trd  3day8  7day8  ]4dq8 2]dayS ど 冒 もl 阜 ● ヽl -i ち FTコ -a -● 盟 A 月 中

Twitch Tension

P P P

⊂〉    rJ   .JL

( k?/cm 2!o

OI Q〉

Half Relaxation Time (msec)

■.l▲

o g 合 雷 告 8 C皇trd  3day8  7day● ]4dayB

IS

仙da -S憲

ロE]田■

Type ll

Type I

Fig. 4 0 0 8 7 0 0 0 0 0 0 0 6 5 4 3 2 1

(%)SJoq!10PSnulOJOqunN

田3days 国7days ∫ 21 days

Type ll

Type l

Fig. 5

0

0

0

3

0  0 0  0

LO 0

2  2

0

0

5

一山劃

0

0

0

1 0  0

0

LO (Nuu)t2巴eJOq!j

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