Control of the mitotic activity in the rat seminal vesicle by "chalone".

One month after castration male rats were injected daily with 2 X 50 mug of testosterone. Starting before the highest mitotic activity of seminal vesicles, 3 injections of normal seminal vesicle extract were given into the lumen at 3 h intervals. The contralateral seminal vesicle was injected with rat liver extract. Tritiated thymidine was given intravenously. The labelling index of the seminal vesicles was determined by means of radioautography. The crude supernatant of seminal vesicle was the most effective to inhibit the mitotic activity of the seminal vesicles. The decrease was on an average 34 per cent. The liver extract did not influence the mitotic activity. When the seminal vesicle extract was fractionated by Sephadex G-25, the largest fraction (M. W. greater than 3000) showed the highest inhibitory activity, whereas the smallest fraction (M. W. less than 1000) was ineffective. The inhibition of mitosis can also be induced by an unspecific factor, since pronase showed slight inhibitory action on seminal vesicle mitosis. However, the seminal vesicle extract had no inhibitory action on the epidermal mitotic activity.