pituitrin and sulprostone

Arginine-vasopressin (AVP) facilitates water reabsorption in renal collecting duct principal cells by activation of vasopressin V2 receptors and the subsequent translocation of water channels (aquaporin-2, AQP2) from intracellular vesicles into the plasma membrane. Prostaglandin E2 (PGE2) antagonizes AVP-induced water reabsorption; the signaling pathway underlying the diuretic response is not known. Using primary rat inner medullary collecting duct (IMCD) cells, we show that stimulation of prostaglandin EP3 receptors induced Rho activation and actin polymerization in resting IMCD cells, but did not modify the intracellular localization of AQP2. However, AVP-, dibutyryl cAMP- and forskolin-induced AQP2 translocation was strongly inhibited. This inhibitory effect was independent of increases in cAMP and cytosolic Ca2+. In addition, stimulation of EP3 receptors inhibited the AVP-induced Rho inactivation and the AVP-induced F-actin depolymerization. The data suggest that the signaling pathway underlying the diuretic effects of PGE2 and probably those of other diuretic agents include cAMP- and Ca2+-independent Rho activation and F-actin formation.

Topics: Actins; Animals; Aquaporin 2; Aquaporins; Biological Transport; Cell Membrane; Cells, Cultured; Colforsin; Cyclic AMP; Cytoplasmic Vesicles; Dibenz(b,f)(1,4)oxazepine-10(11H)-carboxylic acid, 8-chloro-, 2-acetylhydrazide; Dinoprostone; Kidney Medulla; Microscopy, Fluorescence; Models, Molecular; Neurophysins; Prostaglandin Antagonists; Protein Precursors; Rats; Receptors, Prostaglandin E; Receptors, Vasopressin; rho GTP-Binding Proteins; Signal Transduction; Vasopressins

We examined the effect of prostaglandin E2 (PGE2) on antidiuretic hormone (ADH)-dependent Na+ transport and cAMP production in isolated frog skin epithelium. ADH caused an increase in transepithelial Na+ transport and a decrease in cellular potential, indicating an increase in apical Na+ permeability. Subsequent addition of PGE2 decreased Na+ transport and repolarised the cells. The PGE2 receptor EP1/3-selective analogue sulprostone and the PGE2 receptor EP2/3-selective analogue misoprostol were able to mimic the effect of PGE2. ADH increased cellular cAMP levels, whereas PGE2, sulprostone and misoprostol were able to reduce the ADH-dependent cAMP production. Measurements of intracellular Ca2+ concentration ([Ca2+]i) revealed that it was unaffected by both PGE2 and sulprostone. The inhibitory effect of PGE2 on ADH-dependent Na+ transport was also observed in Ca2+-depleted epithelia. We conclude that ADH stimulates transepithelial Na+ transport by increasing cellular cAMP levels, whereas PGE2 inhibits ADH-dependent Na+ transport by activating EP3-type receptors, which decrease cellular cAMP levels. We have found no evidence that [Ca2+]i is involved in the regulation of ADH-dependent Na+ transport by PGE2.

Topics: Algorithms; Animals; Cyclic AMP; Dinoprostone; Epithelium; Female; In Vitro Techniques; Male; Misoprostol; Oxytocics; Rana esculenta; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP3 Subtype; Skin; Sodium; Vasopressins