[The structure and distribution of the interstitial cells in the medullary substance of the kidney].

Under study were peculiar features of the structure and distribution of interstitial cells of medullary substance (ICMS) in different parts of the rat renal papilla. The amount of lipid granules containing precursors of prostaglandin synthesis in ICMS was counted. The maximum lipid granulation of ICMS was found in the papilla center. The electron-microscopic study has recognized 3 types of ICMS: little differentiated (located in the papilla apex), highly differentiated (prevailing in the center) and cells of the transitional type. The degree of lipid granulation of ICMS showing the intensity of the prostaglandin synthesis and the character of distribution of ICMS seem to correlate with the functional heterogeneity of the medullary substance.