title: Temperature dependence if beta-receptor mediated relaxation in rabbit intestine.
abstract: The relaxation induced by isoproterenol, A beta-stimulant, appears more markedly at 25 degrees C (pD2 7.98) than at 37 degree C (pD2 6.88) in rabbit intestine. The isoproterenol-induced relaxation was antagonized by treatment with propranolol but not phentolamine at both 25 degree and 37 degrees C, indicating that the relaxation was mediated via adrenergic beta-receptor. The relaxations induced by papaverine, theophylline and MgCl2 were not influenced by temperature change. Basal tissue cyclic AMP content was higher at 25 degrees C than at 37 degrees C, and isoproterenol increased the tissue cyclic AMP content to a similar extent at 25 degrees C and 37 degrees C in the presence of theophylline. The binding of 3H-dihydroalprenolol (3H-DHA) to beta-receptor did not solve the reason of higher sensitivity to isoproterenol at 25 degrees C than at 27 degrees C. At 37 degrees C isoproterenol was more effective in producing a relaxation in the presence than the absence of ascorbic acid (0.057 mM). It is thought that the temperature dependency of the isoproterenol-induced relaxation may be mainly due to the breakdown of isoproterenol in a high temperature.
mesh_terms: D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D004082:Dihydroalprenolol; D005260:Female; D066298:In Vitro Techniques; D007422:Intestines / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013696:Temperature
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D011433:Propranolol; D000242:Cyclic AMP; D007545:Isoproterenol; D010646:Phentolamine