THE EFFECTS OF HYPOPHYSECTOMY AND BOVINE PROLACTIN ON SALT FLUXES IN FRESH-WATER-ADAPTED FUNDULUS HETEROCLITUS

Abstract

It is now well established that a prolactin-like substance Is necessary for the survival of the hypophysectomized teleost Fundulus heteroclitus in fresh water. In normal fish the Na efflux in fresh water equals the influx (approximately 0.6 [mu][image]/gm/hr). After hypophysectomy the influx remains at 0.6 [mu][image]/gm/hr but the efflux increased to 12 [mu][image]/gm/hr. Ligation of the anus and excretory opening has little effect on the efflux of Na from hypophysectomized fish. Therefore, hypophysectomy seems to be followed by an Increase in the ion permeability of the body surface (gills?). Hypophysectomized fish injected with 20 [mu]g prolactin on 2 consecutive days effluxed Na at a rate of 1.3 [mu][image]/gm/hr. The influx of Na into hypophysectomized fish receiving prolactin was 1.0 [mu][image]/gm/ hr. Thus it seems that prolactin enables survival of hypophysectomized Fundulus heteroclitus in fresh water by lowering the permeability to ions.