Cellular origin and hormonal regulation of K+-ATPase activities sensitive to Sch-28080 in rat collecting duct

Rat collecting ducts exhibit type I or type III K+-ATPase activities when a nimals are fed a normal (NK) or a K+-depleted diet (LK). This study aimed a t determining functionally the cell origin of these two K+-ATPases. For thi s purpose, we searched for an effect on K+-ATPases of hormones that trigger cAMP production in a cell-specific fashion. The effects of 1-deamino-8-D-a rginine vasopressin (dD-AVP), calcitonin, and isoproterenol in principal ce lls, alpha -intercalated cells, and beta -intercalated cells of cortical co llecting duct (CCD), respectively, and of dD-AVP and glucagon in principal and alpha -intercalated cells of outer medullary collecting duct (OMCD), re spectively, were examined. In CCDs, K+-ATPase was stimulated by calcitonin and isoproterenol in NK rats (type I K+-ATPase) and by dD-AVP in LK rats (t ype III K+-ATPase). In OMCDs, dD-AVP and glucagon stimulated type III but n ot type I K+-ATPase. These hormone effects were mimicked by the cAMP-permea nt analog dibutyryl-cAMP. In conclusion, in NK rats, cAMP stimulates type I K+-ATPase activity in alpha- and beta- intercalated CCD cells, whereas in LK rats it stimulates type III K+ATPase in principal cells of both CCD and OMCD and in OMCD intercalated cells.