[Factor inhibiting gonocyte division in the testes of the rabbit fetus]

A factor of protein nature selectively inhibiting the division of gonocytes was isolated from the extracts of testes of the 27 and 29 day old rabbit foetuses by the method of gel-chromatography with Sephadex G-100. Its molecular mass equals 30 000. This factor is also present in the testes of newborn, one month old and adult rabbits. It appears to be involved in the local mechanisms of regulation of spermatogenesis, unlike inhibin acting via the central mechanisms affecting the FSH and LH secretion by the pituitary.