BRANCHIAL SODIUM EXCHANGE IN SEAWATER-ADAPTED TILAPIA MOSSAMBICA: EFFECTS OF PROLACTIN AND HYPOPHYSECTOMY

Abstract

SUMMARY: The effects of exogenous prolactin and hypophysectomy were tested on Na exchange across the gills of Tilapia mossambica adapted to sea-water. Exogenous prolactin produced a 75% decrease of both total Na influx and Na efflux. Total Na influx was measured simultaneously with the drinking rate. Water ingestion stopped almost completely in prolactin-treated fish. Thus branchial net excretion flux of Na was reduced 75% by prolactin. Hypophysectomy produced a 50% inhibition of Na efflux across the gill.