PROLIFERATION OF GUBERNACULUM CELLS INDUCED BY A SUBSTANCE OF LOW-MOLECULAR-MASS OBTAINED FROM FETAL PIG TESTES

To investigate the hormonal control of gubernacular development and te sticular descent we determined the effect of gonadal extracts and vari ous hormones on the proliferation of gubernaculum cell cultures establ ished from 55 male pig fetuses obtained at 60 to 90 days' gestation. T he percentage of descended testes was 0 at 60, 8% at 70, 40% at 80 and 87% at 90 days' gestation. Significant proliferation (as measured by [H-3]thymidine incorporation) of gubernaculum, but not 3T3, cells was induced by crude testicular but not ovarian extracts, and was directly related to its protein concentration. Significant proliferation of gu bernaculum cells was induced by low molecular mass (<30 kD) testicular , but not by high molecular mass (>30 kD), testicular and low or high molecular mass ovarian extracts obtained by centrifugation of crude ex tracts in microspin filter membranes with a molecular cut-off mass of 30 kD. Proliferation of gubernaculum cells induced by the low molecula r mass (<30 kD) testicular extract was significantly greater than that stimulated by testosterone or dihydrotestosterone. Polyacrylamide gel electrophoresis demonstrated a unique protein band at approximately 2 6 kD in the crude and low molecular mass testicular, but not in the ov arian, extracts. It is possible that this represents a novel peptide h ormone secreted by the fetal testis, responsible for stimulating the g rowth of the gubernaculum, thereby mediating testicular descent.