Influence of alpha-adrenergic-receptor activation on junctional conductance in heart cells: interaction with beta-adrenergic adrenergic agonists.
The influence of phenylephrine (10(-6) M) on the regulation of junctional conductance (gj) was investigated in heart-cell pairs isolated from the ventricles of adult rats. The results indicated that phenylephrine reduced gj by 45% (SEM, +/- 3.4; n = 20; p < 0.05) within 2 min of it's administration to the bath. The effect of phenylephrine was dose dependent and was abolished by prazosin (10(-6) M). Moreover, the activation of protein kinase C seems essential for the effect of phenylephrine on gj, because previous inhibition of protein kinase C reduced the effect of the drug. Norepinephrine (10(-6) M) or epinephrine (10(-6) M) increased gj by 56% (SEM, +/- 5.3; p < 0.05; n = 14) and 43.6% (SEM, +/- 4.1; n = 12; p < 0.05), respectively, and their effects were larger in the alpha 1-adrenergic receptor was blocked with prazosin. The results indicate that alpha-adrenergic activation reduces gj and interacts with the influence of beta-adrenergic stimulation on junctional conductance.
De Mello
W C
WC
Department of Pharmacology and Anesthesiology, School of Medicine, University of Puerto Rico, San Juan, USA.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D017629:Gap Junctions / Q000502:physiology*; D006329:Heart Conduction System / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D011493:Protein Kinase C; D011224:Prazosin; D004837:Epinephrine