Effect of cations on resistance and responsiveness of renal and forelimb vascular beds

¹ Environmental Medicine Division, U. S. Army Medical Research Laboratory, Fort Knox, Kentucky; and Departments of Physiology and Medicine, University of Oklahoma Medical Center, Oklahoma City, Oklahoma

The local effects of calcium, magnesium, and potassium on renal vascular resistance were determined in the dog by measuring the renal arterial-venous pressure gradient at constant flow during infusion of isosmotic solutions of KCl, NaCl, MgCl₂, and CaCl₂ into the renal artery. Resistance was increased markedly by CaCl₂, decreased slightly by MgCl₂, and affected irregularly by KCl. However, KCl regularly decreased resistance in constricted kidneys. MgCl₂ decreased the response of the renal vascular bed to locally injected levarterenol and l-epinephrine. Infusion of MgCl₂ or KCl into the brachial artery, in an amount almost without effect on forelimb resistance, decreased the response to intrabrachially injected levarterenol. These findings indicate that, except for differences due to the normally dilated state of the kidney, the effects of calcium, magnesium, and potassium on renal vessels are similar to their effects on forelimb and coronary vessels, and that magnesium and probably potassium depress the sensitivity of renal and forelimb vascular muscle to levarterenol.

Note:
(With the Assistance of Booker T. Swindall)