Granular cells in the juxtaglomerular apparatus in perinatal rats

Granular cell indices (GCI; Dunihue and Robertson, '57) in kidneys of fetal and newborn rats were determined by examining sections stained with Bowie's technique. Some fetuses were delivered prematurely by Caesarean section a day earlier than the expected delivery, and were then nursed by a foster mother. Similarly, postmature Caesarean newborn rats were obtained; retention one day beyond the normal gestation was induced by maternal progesterone injections. The GCI was strikingly increased within a day after birth, followed by an immediate decrease therafter. This was also observed in both premature and postmature rats. It seems that this temporary increase of the GCI is not attributable solely to the age of rat, but follows only the separation from the maternal environment.