INTERACTION OF MAGNESIUM WITH VASOPRESSIN IN INTESTINAL SMOOTH MUSCLE

¹ Departments of Pathology, Presbyterian-University of Pennsylvania Medical Center Research Institute, and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

The effects of vasopressin on intestinal smooth muscle and its interaction with Mg were determined. Vasopressin had a diphasic effect on isolated rings of rabbit colon, consisting of inhibition of spontaneous activity followed by a slight contraction. The inhibitory effects of vasopressin were not blocked by combined alpha and beta adrenergic blocking agents but were potentiated by pronethalol. Atropine had no effect on the response of rabbit colon rings to vasopressin. Guinea-pig taenia and colon rings were not inhibited prior to the contraction produced by vasopressin. Both the inhibitory and excitatory intestinal effects of vasopressin were potentiated by Mg. The inhibition of rabbit colon by epinephrine was not affected by Mg. These results support our previous suggestion that potentiation of the effects of neurohypophyseal peptides by Mg is a general interaction at contractile tissue receptors for these hormones.