Comparative analysis of milt quality and steroid levels in blood and seminal fluid of Persian sturgeon males, Acipenser persicus during final maturation induced by hormonal treatment

Steroids both in seminal fluid (SF) and blood serum (BS) as well as the milt quality (sperm motility and sperm production) were investigated during final maturation of Persian sturgeon. The BS levels of testosterone (T), 11-Ketotestosterone (11-KT), progesterone (P), 17α,20β,21-trihydroxy-4-pregnen-3-one (20βS), cortisol (C) and 17α,hydroxyprogesterone (OHP) elevated after pituitary preparation (PP) treatment and then decreased during stripping period for spermiating males. Such elevations did not occur for non-spermiating individuals and steroids remained in basal levels after PP treatment until the end of stripping period. For both groups (spermiating and non-spermiating fish), the BS levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) did not show significant changes during experiment. During stripping period, the values of all tested steroids were significantly lower in SF than in BS of spermiating males. SF levels of 20βS and 11-KT showed a decreasing trend and the other steroids were unchanged during this period. Significant positive correlations were found between the values of 20βs and 11-KT in BS with their levels in SF. Also, BS and SF levels of 20βs and 11-KT were positively correlated with sperm motility characteristics (percentage and duration of motility) and sperm production (sperm density and milt volume), respectively. The results showed the probable involvement of 20βs, P, OHP, T, 11-KT and C in final maturation of Persian sturgeon, especially 20βs and 11-KT had good correlations with qualitative parameters of milt. The lower levels of steroids in SF than those in BS might also be essential for viability of Persian sturgeon spermatozoa. Probably, there are mechanisms that stabilize the concentrations of a number of hormones in the SF.