Juxtaglomerular cells in mice after long-term treatment with captopril--an electron microscopic study.

In mice, the juxtaglomerular cells were examined using qualitative and quantitative electron microscopy after an administration of captopril. After treatment with captopril for 2, 7 and 14 days, the specific granules were decreased in number, the Golgi apparatus was well developed, and the rough endoplasmic reticulum was dilated in profile. In the dilated rough endoplasmic reticulum, the intracisternal granules were occasionally seen after a 2-day treatment, were increased in size and number after a 7-day treatment and were hardly seen after a 14-day treatment. In a few cells associated with intracisternal granules on the 7th day, the Golgi apparatus was not well developed and some lysosomal bodies containing granules similar to the intracisternal granules were seen. In these cells, an excess of the intracisternal granules may be controlled by lysosomes. These findings suggest that the juxtaglomerular cells stimulate renin synthesis after long-term treatment with captopril, but a further increase in renin synthesis cannot be expected after the 7th day.