FETAL THYMUS AND THYMULIN STIMULATE THE PROLIFERATION OF GONOCYTES IN FETAL-RAT TESTIS INVITRO

Testes from 13.5-day-old rat foetuses were culture in vitro for 1 or 2 days : 1) in synthetic medium; 2) in thymulin- or corticosterone supplemented medium; 3) in co-culture with fragments of foetal thymus; 4) in co-culture with fragments of foetal thymus in corticosterone-supplemented medium. The numbers of germ cells were about 2-fold greater in testes cultured with fragments of thymus, or in thymulin-supplemented medium than in all the other experimental conditions. These results indicated that thymulin can stimulate foetal gonocytes proliferation and that corticosterone inhibits thymulin-stimulated gonocytes proliferation. The data suggest a functional relationship between corticosterone, thymulin and the foetal gonocytes in vivo.