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Original articles  

The Journal of Sports Medicine and Physical Fitness 2001 September;41(3):324-9

language: English

Effect of sustained adrenergic receptors stimulation and blockade on lactate threshold in rats

Zarzeczny R. #*, Langfort J. *, Pilis W. #, Nazar K. *, Kaciuba-Us´cilko H. *, Porta S. **

From the
# Depart­ment of Phys­ical Edu­ca­tion, Uni­ver­sity of Ped­a­gogics, Czes­to­chowa, ­Poland.
* Depart­ment of ­Applied Phys­iology, Med­ical ­Research ­Centre, ­Polish ­Academy of Sci­ences, ­Warsaw, ­Poland
** Insti­tute of Gen­eral and Experi­mental ­Pathology, Insti­tute of Func­tional ­Pathology, Uni­ver­sity of ­Graz, ­Graz, Aus­tria


Back­ground. ­This ­study exam­ined the hypoth­esis ­that pro­longed (12 hrs) stim­u­la­tion of adre­nergic recep­tors by adren­a­line and ­their ­blockade by regi­tine (­α-­blockade) or pro­pran­olol (­β-­blockade) ­affect lac­tate ­thresh-old (TLA) and exer­cise tol­er­ance in ­rats.
­Methods. ­Twenty-­four ­untrained ­male ­Wistar ­rats per­formed a mul­ti­stage run­ning ­test on a tread­mill ­with an inten­sity ­increased ­from 13 m/min to the max­imum ­speed. ­After a con­trol exer­cise ­test the ani­mals ­were ­devided ­into ­three ­groups ­implanted s.c. ­with: 1) adren­a­line; 2) pro­pran­olol and 3) regi­tine tab­lets. ­Twelve ­hours ­after the ­tablet implan­ta­tion the exer­cise was ­repeated. ­Both ­before the exer­cise ­test and at the end of ­each 2-min ­loads ­blood lac­tate [LA] was meas­ured to eval­uate TLA.
­Results. Pro­longed adren­a­line ­excess ­resulted in ­reduced max­imal run­ning ­speed and ­shifted TLA ­towards ­lower exer­cise inten­sities ­than in the con­trol ­test. ­Both ­α- and β-adre­nergic ­blockade ­reduced the ­work ­load at ­which TLA ­occurred, ­without ­changing the max­imum run­ning ­speed and max­imal ­blood LA con­cen­tra­tion. ­Blood [LA] at the lac­tate ­threshold ([LA] at TLA) was sig­nif­i­cantly ­higher in hyper­ad­re­nal­i­nemic ­than in con­trol ­rats, ­whilst ­under ­β-­blockade it was low­ered in com­par­ison ­with con­trol ­values. ­α-adre­nergic ­blockade had no ­effect on [LA] at TLA, but at the ­higher exer­cise inten­sities ­blood [LA] ­exceeded the respec­tive con­trol ­values.
Con­clu­sions. The ­present ­study dem­on­strated ­that pro­longed ­excess of adren­a­line ­reduces the max­imum ­power ­output and TLA. The ­former ­effect ­seems to be a ­result of simul­ta­neous stim­u­la­tion of ­both ­types of adre­nergic recep­tors.

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