Effect of prolactin on loss of solutes via the head region of the early-winter marine threespine stickleback (Gasterosteus aculeatus L., form trachurus) in fresh water.

Abstract

Net loss of sodium chloride and 14C-inulin (at least 14C from injected 14C-inulin) via the head region of the early-winter marine threespine stickleback (Gasterosteus aculeatus L., form trachurus) was studied in an apparatus which permits the suspension of a fish by a rubber diaphragm with its head (including the gills) in continuously oxygenated dechlorinated fresh water, and its trunk in paraffin oil. Under this condition, prolactin injections significantly reduced the net loss of the solutes. Despite this finding with regard to I4C, the prolactin-injected fish showed a lower terminal plasma 14C activity per microliter than the solvent-injected fish. The significance of these findings was discussed.