Effect of FSH on Protein Biosynthesis in Testes of the Immature Rat

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Abstract
Incorporation of amino acid-14C into tricholoracetic acid-precipitable material by testis from 20-day-old rats was measured in vitro. It was concluded that this incorporation Was a measure of testicular protein biosynthesis in that it was time dependent, was abolished by heating the tissue, was neither altered by extracting the precipitate with hot NaCl nor decreased by alkaline hydrolysis, and was inhibited by addition of puromycin in vitro. Protein biosynthesis in the testis of the immature rat was stimulated by FSH administered as a single intraperitoneal injection. The response to FSH was observed with 3 amino acids (lysine-14C, leucine-14C and tyrosine-14C), was time dependent (significant Stimulation was observed 30 min following injection and maximal stimulation was reached after 1 hr), was dose dependent (within the range 0f 0.2 to 200 μg/rat), and was abolished by addition of puromycin in vitro. The stimulation of tiesticular protein biosynthesis by FSH proved to be specific for that hormone and for other gonadotrophins with FSH-like activity (i.e., PMS and HCG). With the placental gonadotrophins, however, the stimulation was not dose dependent. Two lines of evidence demonstrated that the increased protein biosynthesis produced by FSH could not be entirely attributed to enhanced amino acid transport into testicular cells: a) FSH, under conditions where protein biosynthesis was stimulated, did not increase the transport of a-aminoisobutyric acid-I-14C by the tissue, b) Stimulation by FSH was not diminished by increasing the concentration of lysine-14C in the incubation medium (i.e., further addition of substrate of the same specific activity did not result in an increased incorporation into acidprecipitable material). It is concluded that these observations are in keeping with the hypothesis that the action of FSH on the immature rat testis involves accelerated protein biosynthesis. (Endocrinology81: 1151, 1967)