Short-term effects of 17β-estradiol on physiological responses in stellate sturgeon Acipenser stellatus.

There is no evidence of the effect of 17β-estradiol (E2) administration on stress response and related metabolites after a short-period in chondrostean. In this study, we examined whether E2 is capable of inducing the hypothalamus-pituitary-interrenal axis activity. To accomplish this, sexually immature Acipenser stellatus were injected intraperitoneally with saline or E2 (5mg/kg body mass) and sampled 0, 1, 3, 6, 12, 24, 48, and 72h later. Plasma E2, cortisol, glucose, lactate, hematocrit (Hct), total protein (TP), cholesterol, triglyceride, alkaline phosphatase activity (ALP), calcium (Ca), and phosphorus concentrations were examined. Plasma levels of E2 significantly increased after 1h in E2-injected fish and remained high after 12h. E2 injection enhanced plasma TP and Ca concentrations, but had no effect on other parameters. Injection of either saline or E2 enhanced plasma glucose, lactate, TP, and Ca concentrations, but had no effect on Hct, cholesterol, triglyceride, and ALP. The results demonstrated that acutely elevated level of E2 did not lead to intense changes of stress metabolites and altered biochemical changes compared to the fish in control or saline treatment groups. Therefore, we found no exhibition of E2 on the rate of cortisol synthesis or stress indicators in this species, while E2 could modulate some other related metabolites on vitellogenesis pathway.