Cell-specific coupling of PGE2 to different transduction pathways in arginine vasopressin- and glucagon-sensitive segments of the rat renal tubule

摘要

class="enumerated" style="list-style-type:decimal">The aim of the present study was to investigate the transduction pathways elicited by prostaglandin E2 (PGE2) to inhibit hormone-stimulated adenosine 3′:5′-cyclic monophosphate (cyclic AMP) accumulation in the outer medullary collecting duct (OMCD) and medullary thick ascending limb (MTAL) microdissected from the rat nephron.In the OMCD, 0.3 μM PGE2 and low concentrations of Ca²⁺ ionophores (10 nM ionomycin or 50 nM ) inhibited by about 50% a same pool of arginine vasopressin (AVP)-stimulated cyclic AMP content through a same process insensitive to Bordetella pertussis toxin (PTX).Sulprostone, an agonist of the EP1/EP3 subtypes of the PGE2 receptor, decreased AVP-dependent cyclic AMP accumulation in OMCD and MTAL samples. The concentration eliciting half-maximal inhibition was of about 50 nM in OMCD and 0.1 nM in MTAL.In MTAL, 1 nM sulprostone and PGE2 inhibited by about 90% a same pool of AVP-dependent cyclic AMP content through a PTX-sensitive, Ca²⁺-independent pathway.In the OMCD, PGE2 decreased by about 50% glucagon-dependent cyclic AMP synthesis by a process sensitive to PTX and Ca²⁺-independent. Sulprostone 1 nM induced the same level of inhibition.These results demonstrate that PGE2 decrease hormone-dependent cyclic AMP accumulation through a Gαi-mediated inhibition of adenylyl cyclase activity in MTAL cells and glucagon-sensitive cells of the OMCD or through a PTX-insensitive increase of intracellular Ca²⁺ concentration in AVP-sensitive cells of the OMCD.