Polycystic kidney disease induced by corticoids. A quantitative and qualitative analysis of cell populations in the tubular cysts.

The sequential changes of cell morphology and the ratio distribution of the different types of cells which exist in tubular cysts induced by methylprednisolone acetate have been studied by light, transmission and scanning electron microscopy. We have also studied the blood levels of sodium and potassium by flame photometry. In both control and cystic ducts, at the level of the outer cortex, the first intercalated cells (IC) were not observed until the 4th postnatal day. Some intermediate cell configurations were observed during the 3rd postnatal day, suggesting that some primitive principal cells (PC) are transformed into IC. Development of IC seems to be independent of both the effects of corticoids and the blood levels of potassium. The ratio distribution and the types of IC observed throughout the period studied was similar in both normal and cystic ducts. The type of IC characterized by the presence of a huge apical process, which has gone previously undescribed with either TEM or SEM, was observed in both control and cystic ducts. We propose to name these cells as cells with surface pattern type V. During the period of regression of the tubular cysts dead and migrating cells were observed closely associated with cilia of the PC. Both types of cells do not seem to represent, based in their localization and frequency, abnormal cell types of the cyst wall. Our results support the hypothesis that renal cysts are giant collecting ducts which conserve both the morphology and the function of the epithelium.