Circadian Changes in Testosterone and Estradiol-17 Glucuronides and Sulfate Steroids during Spawning Phase in Fresh Water Fish Female Cirrhinus mrigala

The aim of this investigation was to know daily changes (circadian) in the blood plasma free (unconjugated) testosterone (TF) and estradiol-17β(E2F) and its conjugated testosterone glucuronide (TG) and testosterone sulfate (TS) as well as estradiol-17β glucuronide (E2G) and estradiol-17β sulfate (E2S) sex steroids in a mature female fish Cirrhinus mrigala (Ham.) during spawning phase using enzyme-linked immunosorbent assay (ELISA) method. The two sex steroids testosterone and estradiol-17β exhibited identical circadian rhythm: a major peak 29.02±3.58 ng/ml occurred at the onset of the dark phase and a minor peak 12.79±1.89 ng/ml was generally observed 4 hour after the onset of light phase . The TG peak (9.23±1.04 ng/ml was in the dark phase whereas TS during 12.00 PM of dark phase. The E2G 7.19±.76 ng/ml peak was also indicated high during 04.00 am of the dark phase. Result indicated that during the dark phase elevation of free and conjugated sex steroids have important role for spawning, and maintaining the equilibrium of free and conjugated steroids.