Interaction between alpha2-autoreceptors and receptors mediating the effects of angiotensin II and bradykinin in the heart of newborn rats.
The interaction between alpha2-autoreceptors and receptors for angiotensin II and bradykinin was studied in the heart of newborn rats. The tissues were labelled with [3H]noradrenaline and then superfused with cocaine-containing medium and stimulated electrically. Angiotensin II (10-300 nM) and bradykinin (3-100 nM) enhanced the evoked overflow of tritium, the maximum increase reaching 63.2% and 87.1%, respectively. Blockade of alpha2-adrenoceptors by 100 nM yohimbine reduced, and that by 1 microM abolished, the effect of both angiotensin II and bradykinin. On the contrary, chelerythrine and staurosporine--blockers of protein kinase C--as well as forskolin, an activator of adenylyl cyclase and a blocker of phosphodiesterase, markedly enhanced the facilitatory effect of angiotensin II and bradykinin. We conclude that: (1) alpha2-autoreceptors are present in the heart of newborn rats which interact with prejunctional receptors for angiotensin II and bradykinin also present in the rat heart at that age; (2) the facilitatory influence of chelerythrine and staurosporine on the one hand and that of forskolin on the other hand suggests a link between protein kinase C and cyclicAMP pathways.
Mota
Alberto
A
Instituto de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319, Porto, Portugal. avmota@yahoo.com
Guimarães
Serafim
S
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000470:Alkaloids; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017660:Autoreceptors / Q000378:metabolism*; D053119:Benzophenanthridines; D001920:Bradykinin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D011945:Receptors, Angiotensin / Q000502:physiology*; D018002:Receptors, Bradykinin / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000470:Alkaloids; D017660:Autoreceptors; D053119:Benzophenanthridines; D010617:Phenanthridines; D011945:Receptors, Angiotensin; D018002:Receptors, Bradykinin; D000804:Angiotensin II; D005576:Colforsin; D015016:Yohimbine; C016299:chelerythrine; D011493:Protein Kinase C; D019311:Staurosporine; D001920:Bradykinin; D009638:Norepinephrine