Histological and ultrastructural studies of the human juxtaglomerular apparatus in Bartter's syndrome and renal artery stenosis.

Histological and ultrastructural studies of the juxtaglomerular apparatus (JGA) were performed on renal biopsy material from three cases of Bartter's syndrome and two cases of renal artery stenosis. These cases of known JGA hyperfunction were compared with the apparatus in a presumed inactive or basal state as in minimal lesion glomerulonephritis. Light microscopic assessment of the ease of JGA identification, its size and cellularity, provides a valuable reflection of activity and indicates those cases which require ultrastructural assessment of granule turnover. Granule stains often failed to demonstrate any significant increase in granule number in the two conditions studied, and only ultrastructural studies allowed evaluation of secretory activity, rhomboid granule formation and granule release. From these investigations, a proposed mechanism of granule turnover is suggested. The morphological findings in both Bartter's syndrome and renal artery stenosis support the concept of hyperfunction of the apparatus. They may help to elucidate the pathogenesis of Bartter's syndrome and to predict the outcome of surgical intervention in renal artery stenosis. Such studies could profitably be performed on renal biopsies in other disease states, so augmenting our understanding of the contribution of the JGA to the pathogenesis of a variety of glomerular and vascular lesions.