Abstract
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.
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