RENIN LOCATION IN CONTRACTED HUMAN KIDNEYS

In haemodialysed patients with non-functioning contracted kidneys – in some of which nearly all glomeruli were found to be hyalinized and the juxtaglomerular apparatus often unidentifiable – a pronounced hyperplasia of epithelioid-like cells could be demonstrated in the muscular layer of the small cortical arteries. In addition, juxtaglomerular-like granules could be observed in some of these epithelioid cells. The ultrastructure was found to be similar to that of the epithelioid cells of the juxtaglomerular apparatus. In freeze-dried tissue sections from kidneys supravitally stained with Neutral Red, vascular fractions comprising the cortical small arteries, including epithelioid cells, were isolated by microdissection. In these fractions a high renin content was found, in contrast to the low renin activity of the surrounding tubular tissue. The total renin content of the kidney tissue was increased and in most patients plasma renin values were elevated before nephrectomy. It is concluded that, in contracted kidneys, significant amounts of renin are formed outside the juxtaglomerular apparatus in epithelioid cells situated in the media of small arteries, morphologically identical to the epithelioid cells in the afferent arteriole of the normal kidney.