Thyroid hormone and follicle-stimulating hormone regulate M  llerian-inhibiting substance messenger ribonucleic acid expression in cultured neonatal XXXX Sertoli cells.

@entity35 @entity1375 @entity7456 @entity55928
Thyroid hormone is a major regulator of Sertoli cell development, and the present study sought to determine the role of T3 in M  llerian-inhibiting substance ( @entity55928 ) messenger RNA (mRNA) expression. @entity55928 , a Sertoli cell secretory protein that induces M  llerian duct regression and also may be critical for germ and Leydig cell development, is maximal perinatally, then decreases as Sertoli cells mature. The fall in @entity55928 mRNA expression is delayed by @entity1375 in vivo, indicating that T3 could regulate @entity55928 mRNA. However, understanding of the hormonal regulation of @entity55928 has been limited due partly to the lack of a primary Sertoli cell culture system in which sustained expression of @entity55928 or its mRNA can be obtained. We have developed a Sertoli cell culture system for examining hormonal regulation of @entity55928 mRNA. We then tested the effects of T3 and/or FSH treatment on @entity55928 mRNA levels in this new system. Initial studies indicated that @entity55928 mRNA production by 5-day-old @entity35 Sertoli cells was minimal in vitro. Therefore, Sertoli cells from 2-day-old @entity35 were cultured for 2 or 4 days. After 2 days in vitro, steady state @entity55928 mRNA levels were decreased to 36% of the levels seen in freshly isolated Sertoli cells from 2-day-old @entity35 . However, by day 4 of culture, steady state @entity55928 mRNA production had recovered to 67% of that seen in freshly isolated 2-day-old Sertoli cells, which closely paralleled the decrease seen in @entity55928 production in vivo from days 2-6. @entity55928 mRNA levels were decreased 53%, 64%, and 86% in cultures treated with 0.01, 0.1, and 1.0 nM T3 (P < 0.05), respectively. This decrease in Sertoli cell @entity55928 mRNA did not reflect a nonspecific effect on cell viability and/or activity, as shown by a dose-responsive increase in @entity7456 mRNA in these same cultures. FSH (2.5-100 ng/ml) also produced a dose-responsive decrease in @entity55928 mRNA levels, and FSH and T3 together had an additive inhibitory effect on @entity55928 mRNA levels, indicating that these hormones may act through distinct mechanisms. In summary, this is the first primary culture system in which sustained @entity55928 mRNA production can be demonstrated, and it should prove useful for understanding the regulation of @entity55928 in developing Sertoli cells. In addition, T3 and FSH are major regulators of the postnatal decrease in @entity55928 production by the @entity35 Sertoli cell, and these hormones may act through separate pathways.
