[Hyaluronate-hydrolases system and hydroosmotic effect of vasopressin]

Involvement of enzymes catabolizing hyaluronic acid (hyaluronidase, beta-glucuronidase, N-acetyl-beta-D-hexosaminidase) in the hydroosmotic action of vasopressin on the amphibian urinary bladder Rana Ridibunda was studied. It was found that vasopressin (50 nM), agonist of V2 receptors dDAVP (1.5 mcM) and forscolin (30 mcM) induce an activation of enzymes and its release into the Ringer solution at the mucosal surface simultaneously with the increase in the osmotic water flow. Maximal effect was observed 10 min later than hydroosmotic response. Release of enzymes under vasopressin effect was found in the absence of osmotic gradient and water flow through the epithelium. The repeated substitution of the outer Ringer solution for the fresh one resulted in the increase in the both the water permeability and the release of enzymes through the mucosal surface. We suggested that involvement of hyaluronate-hydrolases in the vasopressin effect is mediated by the cAMP-dependent mechanism. It is supposed that this effect creates conditions for the increase in the permeability of glycosaminoglycan structures covering adjacent to the apical cell surface.