Sperm protamine levels as indicators of fertilising potential in sexually mature male rats

Abstract

We have earlier reported that administration of cyproterone acetate, fluphenazine decanoate, tamoxifen citrate, oestradiol valerate to adult male rats, at doses of 50, 5.77, 0.71, 0.28 micromol kg(-1) body weight given for periods of 15, 60, 60, 10 days, respectively, partially suppressed/reduced availability of one or more reproductive hormones viz. LH, FSH, testosterone and reduced their siring ability. The reduction in epididymal sperm counts was not considerable after treatment with these drugs, but conventional methods of assessment of spermatozoa quality viz. sperm chromatin structure assay (SCSA), nuclear chromatin decondensation (NCD) assay, monobromobimane (mBBr) uptake, had shown quantifiable changes in caput sperm chromatin compaction and reduced the testicular levels of protamine 1. The present follow-up study attempts to quantify changes in caudal sperm chromatin which has undergone compaction in the epididymis, in the altered hormonal microenvironment of rats treated with cyproterone acetate, tamoxifen citrate, fluphenazine decanoate, oestradiol valerate, at doses of 50, 5.77, 0.71, 0.28 micromol kg(-1) body weight respectively given for periods of 15, 60, 60, 10 days, with a view to correlating these changes to reduction in their fertilising potential. During the androgen-dependent transit of spermatozoa from caput to cauda epididymis, thiol group oxidation and tyrosine phosphorylation of protamine occurs in maturing sperms concomitant with development of fertilising ability. The results indicate that conventional methods viz. SCSA, NCD, mBBr uptake fail to detect changes induced by hormone deficits in sperm chromatin condensation, as a result of maturation during transit from caput to cauda epididymis. Absence of protamine 1 in epididymal sperm was observed in either testosterone or FSH deficient rats that correlated with reduced fertilising potential. The study suggests that changes in LH/T or FSH affect a hitherto unknown common molecular mechanism in the testis, underlying the protamination of rat spermatozoa. In conclusion, loss of P1 occurs in adult male rats deprived of T or FSH and is a reliable detectable change in epididymal sperm indicative of chromatin condensation defects associated with endocrine imbalance and poor fertility status.