Testicular and serum levels of inhibin and expression of inhibin subunit mRNAs are differentially affected by hemicastration in rats of various ages.

Age-related short-term effects of hemicastration on testicular weight, serum FSH, immunoreactive inhibin, LH and testosterone, testicular levels of inhibin subunit mRNA expression, and bioactive and immunoreactive inhibin were studied in rats of 8, 15 and 22 days of age. Hemicastration led to an increased weight of the remaining testis after 24 h in 8- and 15-day-old rats, but not in 22-day-old rats. Serum FSH levels were elevated in all hemicastrated rats after 8 h. However, serum immunoreactive inhibin levels were decreased only after 72 h in 8-day-old rats and after 24 h in 15- and 22-day-old rats. Inhibin alpha-subunit mRNA expression was increased in the testes of hemicastrated rats of 8 and 15 days of age, whereas inhibin beta B-subunit mRNA expression was elevated in the testes of 15-day-old rats but not in those of 8- and 22-day-old rats. The increase in alpha-subunit mRNA content per testis was caused by an increased concentration and increased testicular weight, whereas the increase in beta B-subunit mRNA in the remaining testis parallelled the increased testicular weight, indicating that different mechanisms play a role in the regulation of these mRNAs. In 22-day-old rats, a transiently decreased expression of inhibin beta B-subunit mRNA was observed 8 h after hemicastration.(ABSTRACT TRUNCATED AT 250 WORDS)