EFFECTS OF HYPOPHYSECTOMY AND PITUITARY REPLACEMENT ON THE PLASMA FREEZING-POINT DEPRESSION, CL-, GLUCOSE AND PROTEIN ANTI-FREEZE IN THE WINTER FLOUNDER (PSEUDOPLEURONECTES-AMERICANUS)

1. 1. The freezing point depression of hypophysectomized winter flounder plasma remained at winter levels during the summer months, whereas the values in sham operated control fish declined. 2. 2. Plasma Cl- and glucose concentrations did not differ between hypophysectomized and sham operated fish. 3. 3. Administration of a winter flounder pituitary homogenate to the hypophysectomized fish for 12 days during the summer resulted in a significant decline in the plasma freezing point depression but did not alter plasma Cl- or glucose concentrations. 4. 4. It was concluded that the pituitary gland is necessary for the disappearance of the protein antifreeze from the plasma during the summer. © 1979.