The effects of long-term thyroxine administration on hematological, biochemical and immunological features in sterlet sturgeon (Acipenser ruthenus)

This study examined the effects of thyroxine (T4) on hematological indices, immune parameters and the stress markers of female sterlet sturgeon. Adult broodstock (708 ± 37 g) were assigned to three groups each consisting of ten females. Fish were injected with coconut oil (control), 1 mg T4 kg body weight−1 in coconut oil (T1) or 10 mg T4 kg body weight−1 in coconut oil (T10). Injections were given intraperitoneally four times over a 170-day treatment period. At the end of the experiment, hemato-biochemical and immunological changes were measured. Treatment with the high concentration of T4 led to a significant increase in weight gain at the end of the experiment. The number of red blood cells, hemoglobin content and hematocrit were also significantly higher in the T10 group compared to the other groups (P < 0.05). The lowest levels of plasma alkaline phosphatase, aspartate amino transaminase and lactate dehydrogenase were found in the T10 group (P < 0.05). Alanine amino transaminase did not differ between groups (P > 0.05). The highest levels of total protein, albumin, complement component 3, complement component 4, and immunoglobulin M were found in the T10 group (P < 0.05). Additionally, higher and lower levels of glucose were noted in T10 and T1 treatments, respectively. Cortisol concentration was highest and lowest in T10 and control groups, respectively (P < 0.05). These findings demonstrate the actions of T4 on multiple regulatory pathways controlling the physiological condition of sterlet sturgeon broodstock.