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The Journal of Sports Medicine and Physical Fitness 1999 March;39(1):42-6

Copyright © 1999 EDIZIONI MINERVA MEDICA

lingua: Inglese

Exercise and beta-adrenergic regulation of rat cardiac myosin isoforms

Wade M. E., Herb R. A., Powers S. K., Criswell D.

Departments of Exercise and Sport Science and Physiology, Center for Exercise Science, University of Florida, Gainesville, Florida, USA


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Background. The pur­pose of ­this experi­ment was to exam­ine the ­effects of ­both exer­cise and β-adre­ner­gic recep­tor block­ade on the expres­sion of ­native car­diac myo­sin iso­forms. Specifically, ­this experi­ment test­ed two hypoth­e­ses: 1) treat­ment of sed­en­tary ­rats ­with the ­beta block­er, pro­pran­o­lol, ­will pro­mote ­increased ven­tric­u­lar V3 (­slow) ­native myo­sin con­tent ­with a con­com­i­tant reduc­tion of V1 (­fast) myo­sin iso­forms; and 2) endu­rance exer­cise train­ing ­will ­result in an ­increased sym­pa­thet­ic ­drive and there­fore ­will ­retard the pro­pran­o­lol-­induced ­shift in car­diac myo­sin iso­form expres­sion.
Methods. Adult, ­male Sprauge-Dawley ­rats (120 ­days old) ­were ran­dom­ly divid­ed ­into 4 ­groups: 1) exer­cise-­sham (ES); 2) exer­cise-pro­pran­o­lol (EP); 3) sed­en­tary-­sham (SS); and 4) sed­en­tary-pro­pran­o­lol (SP). Propranolol (30 mg ­drug/kg ­body wt) and ­sham (­saline) injec­tions (IP) ­were admin­is­tered 30 min­utes ­prior to dai­ly exer­cise. Both ES and EP ­groups com­plet­ed six ­weeks (5 day/wk) of tread­mill run­ning at approx­i­mate­ly 65-70% V.O2max.
Results. Data anal­y­sis ­revealed ­that exer­cise train­ing did not ­alter (p>0.05) ven­tric­u­lar myo­sin iso­forms in the ­sham inject­ed ani­mals. In con­trast, pro­pran­o­lol treat­ment result­ed in a sig­nif­i­cant (p<0.05) ­increase in the ­slow (V3) myo­sin iso­form and a con­com­i­tant ­decrease in the V1 iso­form in ­both sed­en­tary and exer­cise ­trained ani­mals.
Conclusions. The ­observed ­increase in V3 myo­sin iso­form in pro­pran­o­lol treat­ed ­rats sup­ports the ­notion ­that β-adre­ner­gic stim­u­la­tion is an impor­tant reg­u­la­tor of car­diac myo­sin iso­form expres­sion. However, our hypoth­e­sis ­that exer­cise train­ing ­would ­retard the pro­pran­o­lol-­induced ­shift in car­diac myo­sin was not sup­port­ed.

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