The Effect of Hypophysectomy on Sodium Metabolism of the Gill and Kidney of Fundulus Kansae

Renal and extra-renal sodium loss was measured for intact and hypophysectomized Fundulus kansae in fresh water and during adaptation to sea water. 2. In fresh water, urine was copious and dilute but a major route of sodium loss. 3. Following transfer to sea water, urine flow was reduced and extra-renal sodium excretion increased. Renal sodium loss decreased (because of a reduction in urine flow), then increased to above fresh water values, then, after several days in sea water, returned to a low value. 4. Hypophysectomized fish in fresh water had a reduced urine flow, an increased renal sodium loss, while extra-renal sodium outflux was unaffected. 5. Following transfer to sea water, hypophysectomized fish shut-down urine flow and although they increased extra-renal sodium excretion, they did not do so as rapidly as controls. Urine sodium loss was reduced and remained low.