EFFECTS OF MANGANESE ON THE RESPONSE OP AORTIC STRIPS TO ANGIOTENSIN AND NOREPINEPHRINE CONTRACTIONS

¹ Department of Pharmacolgy and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi

Managanese (Mn) Selectively inhibitis calcium (Ca) permeability in certain tissues. This study was undertaken to determine its effects on contraction of rabbit aortic strips induced by norepinephrine and angiotensin.Variation of Ca concentrations be between 0.15 and 2.4 in M had no significant effect on norepinephrine- and angiotensin-induced concentrations. The addition of Mn (0.5 mM) produced a marked decrease in contraction in low Ca solution (0.15 mM). This decrease was prevented in large part at higher. Ca concentrations. Experiments with rabbit aortie strips depolarized by isotonic KCl were conducted to determine the effects of depolarization on the contractile responses. Effects of Mn were similar in depolarized preparations, but appeared less marked. Membrane depolarization produced inhibitory effects on norepinephrine, but not angiotensin contractions. It was concluded that norepinephrine and angiotensin produced contractions both by increasing the Ca permeability of the membrane and by other as yet anknown mechanisms.