Fig. 3.

FSH inhibits Raf kinase activity. A, Total RNA from untreated wild-type Sertoli cells isolated from 15-d-old rats cultured for 5 d was assayed by quantitative real-time PCR. The levels of the mRNAs expressing Raf-1, A-Raf, and B-Raf are shown relative to B-Raf (=1). Values with different lowercase letters differ significantly (P < 0.05) (n = 3). B, Wild-type Sertoli cells were treated with EtOH-vehicle (V), 100 nm testosterone (T), T + FSH (1 μm), or T + FSH + IBMX (I, 0.5 mm) for 10 min. Whole-cell extracts were incubated with purified GST-MEK protein in the presence of ATP, and the relative levels of phosphorylated and total GST-MEK1 were determined by Western blot using antisera against phosphorylated or total MEK½. C, Whole-cell extracts from Sertoli cells treated (B) were assayed by Western blot using antiserum against phosphorylated Raf-1. The blots shown are representative of three independent experiments.