Effect of hydrazine on transport on toad urinary bladder.
Vasopressin stimulates osmotic water flow and urea permeability in the toad urinary bladder via separate cAMP-responsive mechanisms. Hydrazine (10--20 MM), added to the bladder's serosal bath, reversibly enhanced the effect of both low and saturating levels of vasopressin on osmotic water flow, without increasing urea permeability. A small increase in basal water flow was also observed. Cyclic AMP-stimulated water flow was not altered by hydrazine, but hydrazine enhanced the effect of both 8-bromo-cyclic AMP and methylisobutylxantine. Hydrazine increased luminal membrane aggregate frequency in vasopressin-treated tissues examined by freeze-fracture electron microscopy. Hydrazine increased both basal and vasopressin-stimulated adenylate cyclase activity. We could measure no effect of hydrazine on cAMP content; however hydrazine did increase the protein kinase activity ratio (-cAMP/+cAMP) in vasopressin-treated tissues, suggesting that the kinase activity ratio is more sensitive than cAMP content as an index of cAMP-related function in the bladder. Further strengthening the relationship between kinase activation and water flow, we found that methohexital, an inhibitor of vasopressin-stimulated water flow and adenylate cyclase, also decreased the kinase activity ratio in the presence of vasopressin. These studies link closely the role of cAMP-dependent kinase and luminal membrane aggregates to the specific mediation of vasopressin-stimulated water flow in the bladder.
D000818:Animals; D002025:Bufonidae; D002463:Cell Membrane Permeability / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D005260:Female; D006834:Hydrazines / Q000494:pharmacology*; D011453:Prostaglandins / Q000096:biosynthesis; D013395:Sucrose / Q000378:metabolism; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism; D014667:Vasopressins / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects
D006834:Hydrazines; D011453:Prostaglandins; D014667:Vasopressins; D013395:Sucrose; D000242:Cyclic AMP; D006152:Cyclic GMP