PITUITARY AND ADRENOCORTICAL FACTORS IN THE CONTROL OF THE WATER AND ELECTROLYTE COMPOSITION OF THE FRESHWATER EUROPEAN EEL (ANGUILLA ANGUILLA L.)

Abstract

SUMMARY The hypophysectomized eel (Anguilla anguilla L.) in fresh water showed a marked decline in serum Na and Ca concentrations whilst serum K concentration was elevated compared with sham-operated controls. Muscle was hyperhydrated with decline in Na, K and Mg concentrations. The total amount of Na and K/kg. fat-free dried muscle was decreased. The ratio serum [Na]:[K] was lowered. Injection of mammalian prolactin rendered water content normal but not the electrolyte values. Injections of corticotrophin or cortisol brought electrolyte levels towards normal values though muscle hyperhydration was still evident. Injection of prolactin (2 mg./100g. body weight/day) plus cortisol (20 μg./100 g. body weight/day) rendered the values for water and electrolyte composition similar to those for intact and sham-operated controls. The results are discussed in terms of the equivalence of mammalian prolactin to the fish hormone, paralactin, and of cortisol as a prime agent in controlling electrolyte balance in the Teleostei.