THE JUXTAGLOMERULAR APPARATUS IN RENAL ALLOGRAFT REJECTION: HISTOLOGICAL AND ULTRASTRUCTURAL STUDY.

In the canine renal allotransplanted model, typical granular cells are present in the afferent arterioles, and the granulation index of those cells increased as the rejection process progressed. Electron microscopic study confirmed that there is an increase in the number of granules in these epithelial cells which exhibited two types of intracytoplasmic granules: the specific type with secretory droplets, and the non-specific with heterogenous content, similar to digestive vacuoles. The first type predominates in the examined series and seems to represent a mixture of grannies with some degree of storage. The presence of specific granules with crystalloid appearance is a less frequent phenomenon and seems to represent early hormonal production. The pressence in the granular cells of myofilaments and attachment bodies, characteristic of smooth muscle cells, suggests the possibility that those granular cells may be due to metaplasia of pre-existing smooth muscle cells, Plasma erythropoietin levels correlate well with the increased JGI seen in rejection. On the other hand, plasma renin activity docs not correlate with blood pressure changes or with the granulation activity of the juxtaglomerular apparatus. The hemodynamic changes following the rejection process, which resulted in severe renal hypoxia in the examined model, may be a factor in explaining the relationships between JGI and peripheral hormonal levels. [ABSTRACT FROM AUTHOR]