Atrial natriuretic peptide relaxes arterial basal tone induced by coarctation hypertension.
We have investigated the vasorelaxant effect of atrial natriuretic peptide (ANP) on isolated non-contracted aorta from coarctation hypertensive rats (HR) and the role of endothelium in this vasorelaxant action. After 7-14 days of surgery, mean blood pressure was higher (P < 0.01) in HR compared with sham operated rats (SR), used as the control. ANP (10(-6) mol/l) significantly lowered basal tone in previously unstimulated HR thoracic aortic rings; however, it had no effect in HR abdominal aorta or in SR abdominal and thoracic aorta. Endothelial destruction potentiated the vasorelaxant effect of ANP on basal tone in HR thoracic aorta. A similar potentiation of the ANP-response was observed by pre-treatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 3 x 10(-4) mol/l) or methylene blue (2 x 10(-5) mol/l) in unrubbed HR thoracic aorta. Treatment with calcium-free Krebs + EGTA (2 x 10(-3) mol/l) + sodium nitroprusside (10(-5) mol/l) or calcium-free Krebs significantly decreased basal tone and abolished ANP-response. These effects were observed only in HR thoracic aorta. Similarly, staurosporine (10(-7) mol/l) and calphostin C (10(-6) mol/l), inhibitors of protein kinase C (PKC), diminished basal tone and abolished the ANP-response in HR thoracic aorta. Acetylcholine (10(-6) mol/l) had a small but significant action on the basal tone of unrubbed HR thoracic aorta. These results demonstrate that ANP has a vasorelaxant effect on aortic basal tone when the vessel is exposed to high blood pressure. Inhibition of ANP effects on basal tone by calcium-free Krebs and PKC antagonists suggests that the HR aorta increases Ca2+-active tone, that modifies the response of vascular smooth muscle to the vasodilating hormone ANP.
Peral de Bruno
M
M
Department of Physiology, INSIBIO-Universidad Nacional de Tucuman, Argentina. acovi@tubbs.com.ar
Romano
L
L
Proto
M
M
Coviello
A
A
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001012:Aorta, Abdominal / Q000601:surgery; D001013:Aorta, Thoracic / Q000187:drug effects*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
D009320:Atrial Natriuretic Factor; D011493:Protein Kinase C; D000109:Acetylcholine; D002118:Calcium