HISTOAUTORADIOGRAPHICAL AND ELECTRON MICROSCOPICAL STUDIES OF THE PRENATAL ADRENAL MEDULLA IN SPONTANEOUSLY HYPERTENSIVE RAT

Abstract

and fine structure of the adrenal medulla in Spontaneously Hypertensive Rat (SHR, Okamoto and Aoki) was examined in the prenatal stage. The labeling index of the fetal adrenal medulla in SHR was 10}1.38 on the 20th day of gestation and became lower on the 22nd day of gestation. This tendency was consistent with the decrease of mitotic index. The autoradiographical grain count per labeled cell on the 20th day of gestation didn't differ from that on the 22nd day of gestation. These results indicate that the generation time of the adrenal medullary cell in SHR became more longer on successive day of gestation. However, there was no significant difference of the histology and histoautoradiography between SHR and control. Ultrastructurally, most of medullary tissue on the 20th day of gestation were composed of the intermediate cells containing many intermediate granules. These granules increased in number during the fetal life. In most of the adrenal medullary cells, the fine structure was similar to that observed in the control group. These findings suggest that the difference of cell proliferation and cell differentiation in the adrenal medullary cells between SHR and control appears after birth, because the significant difference in the medullary cells of both groups has previously reported in the adult rats.