Changes in Plasma Level of Steroid Hormones (Estradiol 17β, 17α20β Hydroxy Progesteron and Cortisol) and Electrolytes, During Different Stages of Reproductive Cycle in Rutilus rutilus caspicus from Bandar Torkaman (South of Caspian Sea)

The present study aimed to evaluate the changes of estradiol-17β (E2) and 17α20β- hydroxy progesterone (17OHP), cortisol and some electrolytes (Ca2+, K+ and Na+) in the plasma of female R. rutilus caspicus during annual reproductive cycle. Plasma level of steroids was measured using RIA, cortisol using ELIZA and electrolytes using flamephotometry technic. The highest plasma level of E2 (147.16±9.01 ng/ml) was measured at the end of vitellogenesis stage of oocytes. On the contrary, maximum plasma level of 17OHP (4.71±0.64 ng/ml) and cortisol (12.67±2.25 ng/ml) was observed in early April just before spawning time. The maximum concentration of Ca2+ was observed during the vitellogenesis stage of oocytes and then decreased when vitellogenesis progressed. The highest level of K+ decreased sharply in maturation stage of oocytes (P>0.05). The results of the present study revealed that changes in plasma levels of steroids and electrolytes were closely correlated to ovarian development during reproductive cycle.