Abstract
A morphometric study of gonadal interstitial cells in 16 equine fetuses, ranging in age from 120 to 330 days of fetal age, was done to assess the possible relationship of fetal gonads to high plasma concentrations of immunoreactive inhibin in pregnant mares during the second half of pregnancy with its peak at about 280 days of gestation, which has been reported recently. Interstitial cells of fetal gonads underwent progressive hypertrophy to reach a maximum size around 250 days of gestation, and subsequent degenerative changes in these cells resulted in a rapid decrease in the volume density and size of the interstitial cells. Thus, the morphometric change in the interstitial cells was almost synchronous with high concentrations of immunoreactive inhibin in the plasma of pregnant mares. This observation, taken in conjunction with the fact that inhibin α-chain (1-30) was detected immunohistochemically in the cytoplasm of the interstitial cells, appears to provide morphometric evidence that the interstitial cells in fetal gonads are closely related to inhibin production.
