Sites of renin production in fetal, neonatal, and postnatal Syrian hamster kidneys

Renin is first observed in the 14-day fetal kidney. There is a sharp increase in the number of renin positive cells in the 15-day fetal kidney. Renin is located in the smooth muscle cells of arterioles, interlobular arteries, and branches of the renal artery. In the neonatal kidney, the amount of renin appears to be equal to that observed in the 15-day fetal kidney and is still located in the same blood vessels. In the 24-hour postnatal kidney, there is a sharp decrease in the total amount of renin. Renin positive cells are now observed at the vascular pole. In the 48-hour postnatal kidney, there is a sharp increase in the total amount of renin. Most of the renin positive cells are located at the vascular poles; however, a few renin positive cells are seen in the interlobular arteries.