AR versus ER (α) expression in the testis and pituitary following chronic estrogen administration in adult rat

Modulation of the testis-pituitary axis has direct relevance to the expression of androgen and estrogen receptors. Androgen receptor (AR) and estrogen receptor (ERα) expression during hypospermatogenesis after chronic estrogen administration to rats was studied in the adult testis and pituitary utilizing immunohistochemistry, western blotting, and RT-PCR. Both organs demonstrated higher AR transcriptional activity gradually increasing from 15 days (d) to 30 d of estrogen treatment. However, the AR protein as measured by either immunostaining or western blotting demonstrated a significant decline. A distinct break down of the AR protein in the pituitary into two specific bands was seen. In contrast, higher ERα transcriptional activity coincided well with the rise in protein and immunoexpression in both organs. FSH and testosterone (serum, intra-testicular testosterone) were found significantly (p < 0.001) lowered compared with raised estradiol levels. Spermatogenesis was adversely affected and was associated with a significant increase in cell apoptosis in both organs. The pituitary demonstrated a higher rate of apoptosis at the end of 30 d of estrogen treatment. Taken together, the above data indicate that chronic estrogenization to adult rats up-regulates ERα but down-regulates AR protein expression in testis and pituitary which probably has a direct association to the marked rise in cell apoptosis in these organs.