Role of prostaglandin E (PGE) in the modulation of the action of vasopressin on water flow in the urinary bladder of the toad and mammalian kidney.

PGE1 and PGE2 are known to interfere with the water permeability effect of vasopressin in toad bladder and kidney. It has been proposed that endogenous prostaglandin E (PGE), synthesized within cells of vasopressin-sensitive tissues, serves to modulate the permeability changes elicited by the neurohypophyseal hormone. Direct evidence in support of this hypothesis is as follows: vasopressin increases the biosynthesis of PGE2 in renal interstitial cells and in isolated toad bladder. In the latter, inhibition of vasopressin-induced synthesis of PGE by a variety of inhibitors results in a greater water permeability response to vasopressin. It appears that vasopressin has two effects in toad bladder and kidney: (i) it activates adenylate cyclase thereby increasing the concentration of adenosine 3',5' monophosphate (cyclic AMP), the nucleotide responsible for the resultant increase in water permeability; and (ii) it activates a phospholipase that serves to release arachidonic acid, the precursor of PGE2 from intracellular pools. The PGE derived from the arachidonic acid diminishes adenylate-cyclase activity, in consequence of which the response of the enzyme to vasopressin is modulated.