Type II cAMP-dependent protein kinase regulates electrogenic ion transportin rabbit collecting duct

cAMP mediates many of the effects of vasopressin, prostaglandin E-2 and bet a-adrenergic agents upon salt; and water transport in the renal collecting duct. The present studies examined the role of cAMP-dependent protein kinas e (PKA) in mediating these effects. PKA is a heterotetramer comprised of tw o regulatory (R) subunits and two catalytic (C) subunits. The four PKA isof orms may be distinguished by their R subunits that have been designated RI alpha, RI beta, RII alpha, and RII beta. Three regulatory subunits, RI alph a, RIIa, and RII beta, were detected by immunoblot and ribonuclease protect ion in both primary cultures and fresh isolates of rabbit cortical collecti ng ducts (CCDs). Monolayers of cultured CCDs grown on semipermeable support s were mounted in an Ussing chamber, and combinations of cAMP analogs that selectively activate PKA type I vs. PKA type II were tested for their effec t on electrogenic ion transport. Short-circuit current (I-sc) was significa ntly increased by the PKA. type II-selective analog pairs N-6-monobutyryl-c AMP plus 8-(4-chlorophenylthio)-cAMP or N-6-monobutyryl-cAMP plus 8-chloro- cAMP. In contrast the PKA type I-selective cAMP analog pair [N-6-monobutyry l-cAMP plus 8-(6-aminohexyl)-amino-cAMP] had no effect on I-sc. These resul ts suggest PKA type II is the major isozyme regulating electrogenic ion tra nsport in the rabbit collecting duct.