AVP-INDEPENDENT HIGH OSMOTIC WATER PERMEABILITY OF FROG URINARY-BLADDER AND AUTACOIDS

In the isolated frog urinary bladder a 20- to 50-fold increase of the osmotic water permeability has been revealed in the absence of arginin e vasopressin (AVP) as a result of several successive changes of the s erosal Ringer solution. This increase of the osmotic water permeabilit y was of the same magnitude as that of the effect of 1 nM AVP. Similar ly to the effect of AVP, the amount of adenosine 3',5'-cyclic monophos phate (cAMP) in the cells rose, and aggregates of intramembraneous par ticles were formed in the apical plasma membrane of granular cells (as shown by the freeze-fracture method). Immunocytochemical studies usin g anti-actin monoclonal antibodies indicated depolymerization of F-act in following the AVP-independent change in water permeability. It was possible to decrease the high level of osmotic permeability to the ini tial level if 10 mu l/ml of frog blood serum or a lipid extract of thi s blood serum, or 1 mu M arachidonic acid or 1 nM prostaglandin E(2) w as added to the serosal Ringer solution. The rapid restoration of the osmotic water impermeability of the epithelium after the AVP-evoked ef fect was achieved by the addition to the serosal Ringer solution of Ri nger solution in which intact frog urinary bladders had been previousl y incubated for 1 h. The data obtained indicate that the maintenance o f the impermeability to water of the osmoregulating epithelium and the restoration of the initial low level of the osmotic permeability afte r the effect of AVP are due to participation of prostaglandin E(2) and other autacoids as well as, probably some physiologically active subs tances of a lipid nature that are present in the blood serum.