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THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS
Rivista di Medicina, Traumatologia e Psicologia dello Sport
Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,111
The Journal of Sports Medicine and Physical Fitness 2001 September;41(3):324-9
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. **
# 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.