Differential effects of phentolamine on the responsiveness of aortic and femoral smooth muscle from normotensive and DOCA/NaCl hypertensive rats.
The in vitro responsiveness of rat aortic and femoral arterial smooth muscle from normotensive and deoxycorticosterone acetate (DOCA)/NaCl-induced hypertensive rats to potassium chloride (KCl) and isoproterenol (ISO) in the presence and absence of the alpha-adrenergic blocker phentolamine was investigated. Femoral but not aortic smooth muscle from the DOCA/NaCl rat exhibited an enhanced sensitivity to KCl stimulation when compared to controls. Phentolamine had no effect on femoral smooth muscle from control or DOCA/NaCl rats. However, a significant decrease in the sensitivity of aortic smooth muscle responsiveness to KCl in the presence of phentolamine was observed in both the control and hypertensive groups. Isoproterenol-induced relaxation of both aortic and femoral smooth muscle was significantly attenuated in the DOCA/NaCl rat when compared to controls. Incubation with phentolamine resulted in a significant increase in the relaxation response to ISO in aortic and femoral smooth muscle from controls. This increased responsiveness, however, was not observed in DOCA/NaCl rats. The contractile response to high doses of ISO was attenuated with phentolamine in all groups. A significant increase in the sensitivity to norepinephrine (NE) was observed in both aortic and femoral smooth muscle from the DOCA/NaCl rat when compared to controls. Whereas aortic and femoral smooth muscle from the DOCA/NaCl rat which had been exposed to phentolamine previously in the experiment exhibited a significant decrease in the sensitivity to NE following a one hour washout of the phentolamine, no long-lasting effect of phentolamine was apparent in vessels from controls. The results of this study confirm previous studies that the vascular smooth muscle responsiveness to NE is increased and ISO-induced relaxation is decreased in the DOCA/NaCl rat and demonstrate that these altered adrenergic responses are similarly manifested in the femoral smooth muscle.(ABSTRACT TRUNCATED AT 400 WORDS)
D000818:Animals; D001011:Aorta / Q000187:drug effects; D003900:Desoxycorticosterone; D005263:Femoral Artery / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride
D003900:Desoxycorticosterone; D012965:Sodium Chloride; D011189:Potassium Chloride; D007545:Isoproterenol; D009638:Norepinephrine; D010646:Phentolamine