Temperature sensitive effects of alpha-adrenergic stimulation in mouse ventricular myocardia.
The effects of alpha- and beta-adrenergic stimulation on the contractile force and L-type Ca2+ channel current were studied in mouse ventricular myocardia at two different temperatures. In ventricular tissue, at 35-36 degrees C, phenylephrine, in the presence of propranolol, produced a sustained negative inotropic response with no change in the time course of contraction and relaxation. These effects were greatly reduced at 22-23 degrees C. Isoproterenol produced marked positive inotropic responses accompanied by shortening of the time required for relaxation. In isolated ventricular myocytes, phenylephrine, in the presence of propranolol, significantly increased the L-type Ca2+ channel current (I(Ca)) at 35-36 degrees C, but the effect was small at 22-23 degrees C. Isoproterenol increased I(Ca) similarly at both temperatures. These results suggest that, in mouse ventricular myocardia, alpha-adrenoceptor mediated regulation of the contractile force and I(Ca) involve temperature-dependent mechanisms different from those of beta-adrenoceptor-mediated mechanisms.
Nishimaru
K
K
Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
Sekine
T
T
Tanaka
Y
Y
Tanaka
H
H
Shigenobu
K
K
D000322:Adrenergic Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D006352:Heart Ventricles / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013696:Temperature
D000322:Adrenergic Agonists; D000319:Adrenergic beta-Antagonists; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D011433:Propranolol; D007545:Isoproterenol