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Titolo:
K-MUSCLE DURING STEPWISE BICYCLE EXERCISE WITH AND WITHOUT BETA-ADRENOCEPTOR BLOCKADE( SHIFTS OF SKELETAL)
Autore:
HALLEN J; GULLESTAD L; SEJERSTED OM;
Indirizzi:
NATL INST OCCUPAT HLTH,DEPT PHYSIOL N-0033 OSLO NORWAY UNIV OSLO,ULLEVAAL HOSP,EXPTL MED RES INST N-0407 OSLO NORWAY
Titolo Testata:
Journal of physiology
fascicolo: 1, volume: 477, anno: 1994,
pagine: 149 - 159
SICI:
0022-3751(1994)477:1<149:KDSBEW>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAT SOLEUS MUSCLE; PLASMA-CATECHOLAMINES; BLOOD-FLOW; POTASSIUM; TRANSPORT; NA; STIMULATION; PERFORMANCE; QUANTIFICATION; ACTIVATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
43
Recensione:
Indirizzi per estratti:
Citazione:
J. Hallen et al., "K-MUSCLE DURING STEPWISE BICYCLE EXERCISE WITH AND WITHOUT BETA-ADRENOCEPTOR BLOCKADE( SHIFTS OF SKELETAL)", Journal of physiology, 477(1), 1994, pp. 149-159

Abstract

1. K+ efflux rate and control of K+ reuptake rate in exercising muscle cells was examined in six healthy female volunteers. 2. A K+-selective electrode in the femoral vein continuously monitored K+ concentration ([K+](fv)) during bicycling. Power was increased stepwise 5-6 timesby 30-40 W every fourth minute until exhaustion before and after I.V.administration of propranolol. Leg blood flow was measured by bolus injections of Cardiogreen. 3. [K+](fv) increased from about 4.3 to 6.8 mmol l(-1) at exhaustion both before and after propranolol administration, but after drug infusion endurance was reduced from 22.2+/-0.6 to 19.7+/-1.1 min, so [K+](fv) rose more rapidly. 4. The exercise-inducedefflux rate of K+ from the muscle cells was estimated to be about 11 mu mol kg(-1) s(-)1 at exhaustion both before and after propranolol administration. 5. As an indicator of rate of net loss of K+ from the leg, veno-arterial concentration differences ([K+](fv-a)) during first, fourth and fifth power increments were high after 15 and 40 s, but declined toward the end of each power step. Propranolol accentuated [K+](fv-a) only after 15 and 40 s of the first and fourth increments. 6. The exercise-induced increase in reuptake rate of K+ in the muscle, estimated at exhaustion, was not significantly changed by propranolol and was about 10 mu mol kg(-1) s(-1), corresponding to about 15 % of maximum Na+-K+ pump capacity in man. 7. Extracellular accumulation and lossof K+ from muscle during bicycle exercise is due to Na+-K+ pump lag. The higher [K+](fv) during propranolol is mainly due to impaired redistribution outside the exercising muscles. In addition at low powers, beta-adrenoceptor blockade caused a transiently increased net loss due to an accentuated Na+-K+ pump lag.

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Documento generato il 05/12/20 alle ore 20:23:40