title: Effect of sustained adrenergic receptors stimulation and blockade on lactate threshold in rats.
abstract: BACKGROUND
  This study examined the hypothesis that prolonged (12 hrs) stimulation of adrenergic receptors by adrenaline and their blockade by regitine (alpha-blockade) or propranolol (beta-blockade) affect lactate thresh-old (T(LA)) 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 T(LA).
  
  
  RESULTS
  Prolonged adrenaline excess resulted in reduced maximal running speed and shifted T(LA) towards lower exercise intensities than in the control test. Both alpha- and beta-adrenergic blockade reduced the work load at which T(LA) occurred, without changing the maximum running speed and maximal blood LA concentration. Blood [LA] at the lactate threshold ([LA] at T(LA)) was significantly higher in hyperadrenalinemic than in control rats, whilst under beta-blockade it was lowered in comparison with control values. Alpha-adrenergic blockade had no effect on [LA] at T(LA), 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 T(LA). The former effect seems to be a result of simultaneous stimulation of both types of adrenergic receptors.
authors.affiliation: Department of Physical Education, University of Pedagogics, Czestochowa, Poland. r.zarzeczny@wsp.czest.pl
authors.forename: R
authors.initials: R
authors.lastname: Zarzeczny
authors.forename: J
authors.initials: J
authors.lastname: Langfort
authors.forename: W
authors.initials: W
authors.lastname: Pilis
authors.forename: K
authors.initials: K
authors.lastname: Nazar
authors.forename: H
authors.initials: H
authors.lastname: Kaciuba-Uścilko
authors.forename: S
authors.initials: S
authors.lastname: Porta
mesh_terms: D000322:Adrenergic Agonists / Q000494:pharmacology*; D018674:Adrenergic Antagonists / Q000494:pharmacology*; D000818:Animals; D004343:Drug Implants; D004837:Epinephrine / Q000494:pharmacology; D017079:Exercise Tolerance / Q000187:drug effects / Q000502:physiology*; D007773:Lactates / Q000097:blood*; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000502:physiology*; D012420:Running / Q000502:physiology
chemical_list: D000322:Adrenergic Agonists; D018674:Adrenergic Antagonists; D004343:Drug Implants; D007773:Lactates; D011941:Receptors, Adrenergic; D011433:Propranolol; D004837:Epinephrine; D010646:Phentolamine