Ca++ and Mg++ effects on toad bladder response to cyclic AMP, theophylline, and ADH analogues

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Abstract
Ca, 10 m[image], in the solution bathing the serosal surface of the toad bladder inhibits the effect of submaximal concentrations of neurohypophyseal hormones (ADH) on osmotic flow of water and on permeability of the bladder to urea, but does not inhibit the effect of these preparations on active Na transport. In the present study, 10 m[image] Ca inhibited the effect of Pitressin and arginine vaso-pressin on osmotic water flow but not that of lysine vasopressin, oxytocin, arginine vasotocin, theophylline, and cyclic 3[image], 5[image]-AMP. Ca, 10m[image], affected the urea permeability response to these agents in a manner parallel to its effect on osmotic water flow. Mg, 8 m[image], inhibited osmotic water flow response to all substances tested excet cyclic 3[image], 5[image]-AMP. The data support the hypothesis of Petersen and Edelman that there are separate types of sites of ADH-induced cyclic 3[image], 5[image]-AMP production: those related to Na transport, and those related to water and urea permeability. The present data are also consistent with the view that changes in osmotic flow and urea permeability are mediated by a single pool of cyclic 3[image], 5[image]-AMP.

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