EFFECT OF SOMATOLACTIN AND RELATED HORMONES ON PHOSPHATE-TRANSPORT BYFLOUNDER RENAL TUBULE PRIMARY CULTURES

Winter flounder renal proximal tubule primary monolayer cultures mount ed in Ussing chambers were used to determine the effect of salmon soma tolactin (sSL) on transepithelial P-i and Ca2+ transport. sSL stimulat ed P-i reabsorption in a dose-dependent manner at physiological levels of the hormone (12.5 ng/ml). Net P-i transport was significantly alte red by sSL (200 ng/ml) within 2 h after the initial exposure. Ca2+ flu xes were unchanged by the addition of 200 ng/ml sSL. The sSL-induced P -i reabsorption was abolished by 10 mu M H-89, a highly specific prote in kinase A inhibitor. Moreover the production and release of adenosin e 3',5'-cyclic monophosphate were significantly increased after 1 and 2 h of exposure to sSL. The data indicate that sSL directly stimulates net renal P-i reabsorption by an adenosine 3',5'-cyclic monophosphate -dependent pathway. In addition to sSL, flounder SL and rat prolactin greatly, and salmon growth hormone (2.3 mu g/ml) slightly, increased n et P-i reabsorptive flux, whereas salmon prolactin had no effect.