Relaxant effects of alpha-human atrial natriuretic peptide on venous smooth muscle.
1 The present study has examined the relaxant effects of alpha-human atrial natriuretic peptide (alpha-hANP) and sodium nitroprusside on dog saphenous vein ring preparations; responses were tested on a background of tone corresponding to 30% and 80% of maximal contraction. Also tested on the lower background of tone were the responses to carbachol, M&B 22,948, forskolin and 3-isobutyl-1-methylxanthine (IBMX). The vascular responses to alpha-hANP and carbachol were also examined in dog splenic artery ring preparations. 2 On a background of tone corresponding to 30% of maximal contraction, both alpha-hANP and sodium nitroprusside were found to relax venous ring preparations with IC50 values of 6 x 10(-8) and 2 x 10(-7) M, respectively. When the background of tone was raised to 80% of maximal contraction, the relaxant effect of sodium nitroprusside was significantly reduced and that of alpha-hANP became almost completely abolished; the IC50 value for sodium nitroprusside in these experimental conditions was 2 x 10(-6) M. 3 The cGMP phosphodiesterase inhibitor M&B 22,948 was found to produce a concentration-dependent relaxation, with an IC50 value of 2 x 10(-6)M in saphenous vein rings with a background of tone corresponding to 30% of maximal contraction. By contrast, saphenous vein rings were found to be insensitive to carbachol. Forskolin and IBMX were also found to produce concentration-dependent relaxing responses of venous preparations, with IC50 values of 2 x 10(-7) and 7 x 10(-7) M, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Villanueva
M M
MM
Laboratório de Farmacologia, Faculdade de Medicina, Porto, Portugal.
Nunes
J P
JP
Soares-da-Silva
P
P
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000032:analysis; D006152:Cyclic GMP / Q000032:analysis; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D011688:Purinones / Q000494:pharmacology; D012501:Saphenous Vein / Q000187:drug effects; D013157:Splenic Artery / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
D010446:Peptide Fragments; D011688:Purinones; D009599:Nitroprusside; D005576:Colforsin; D009320:Atrial Natriuretic Factor; D002217:Carbachol; D000242:Cyclic AMP; C011145:zaprinast; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine