Effects of adrenaline, angiotensin, potassium and calcium on lanthanum treated portal veins.
Lanthanum (La) [3 X 10(-4M] suppressed spontaneous phasic contractions of the islated rat portal vein. Removal of La from the bath solution did not restore this effect. La treated quiescent veins developed dose-dependent contractures after cumulative exposure to adrenaline, angiotensin or K. It then became possible to obtain S-shaped curves relating K concentration to tension development. This relationship was shifted to the left by increasing Ca or decreasing Na concentrations of the incubation medium. Ca dose-response curves were obtained out on previously Ca-depleted La treated veins after stimulation by K, adrenaline or angiotensin. Curves from veins exposed to adrenaline were placed to the left compared with those exposed to depolarizing solutions. This observation supports the view that drugs such as adrenaline may act by increasing Ca inward movement through the plasma membrane beyong that elicited by mere depolarization. Angiotensin evoked small contractile responses, thus showing that La treatment exerts differential blocking effects on the responses to vasoactive compounds.
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D011169:Portal Vein / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats
D000804:Angiotensin II; D007811:Lanthanum; D011188:Potassium; D002118:Calcium; D004837:Epinephrine