[The relationship of mesangial cells to the renal juxtaglomerular apparatus].

A comparison between the ultrastructural characteristics of mesangial cells and myoepithelioid ones of the juxtaglomerular apparatus (JGA) of the kidney was carried out under conditions of activation and reduction in the secretion of renin. Bilateral adrenalectomy and parenteral protein loading were used for intensifying the activity of JGA. The state of a decreased functional activity of the JGA was studied under conditions of 7-day starvation. It was established that both in the case of adrenalectomy and in protein loading mesangial and myoepitheloid cells showed a similar type of reaction, the essence of the latter being activation of the protein synthesis. Moreover, in mesangial cells there were observed secretory granules similar structurally to those of the myoepithelioid cells. A-Decrease in secretion in myoepithelioid cells of the JGA in starvation was accompanied at the same time by a reduction in the synthetic activity of mesangial cells. An analogous reaction of mesangial and myoepithelioid cells in activation and reduction of renin secretion justifies the suggestion about the functional unity of these cells in producing biologically active substances of the JGA of the kidney.