Diurnal variations in prolactin secretion and serum Na+ and K+ concentrations in the freshwater catfish. Clarias batrachus.

Variations in the pituitary gland and blood serum prolactin levels along with Na+ and K+ ions concentrations during 24 hr period were studied in Clarias batrachus. Prolactin secretion exhibited clear diurnal rhythm. Peaks in the prolactin content of pituitary and serum were recorded at early photophase 06.00 and 09.00 hr respectively. Troughs in the both pituitary and serum were noticed during mid darkphase at zero hour (24.00 hr). The concentration of serum Na+ and K+ ions also demonstrated marked diurnal changes but unlike prolactin levels, the highest cation concentrations were encountered during mid darkphase and the lowest at the middle of photophase. Apparently, there was no relationship between changes in prolactin secretion and Na+ and K+ ions concentrations.