Focal distribution of surface marker enzymes after long-term culture of adult rat bladder epithelium and methylnitrosourea (NNU)-induced bladder tumors.

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Abstract
Cytochemical techniques showed that alkaline phosphatase was associated with the plasma membrane of basal and intermediate cells in normal adult rat bladder epithelium. 5''-Nucleotidase was associated with the plasma membrane of basal, intermediate and superficial cells, including the asymmetric membrane. Normal localization of both enzymes was maintained in explants for up to 2 mo., in the organized areas of the culture where epithelium and stroma were still in their normal relationship. In epithelial outgrowths, maintained in culture for up to 8 mo., the localization of both enzymes was abnormal: alkaline phosphatase was detected in some cells as large deposits of reaction product associated with the external surface of the plasma membrane (extramembranous) and in other cells as smaller deposits within the plasma membrane (intramembranous) and in mitochondria; 5''-nucleotidase, initially detected as extramembranous deposits was lost from the outgrowth after 15 days in culture. N-methyl-N-nitrosourea (MNU)-induced rat bladder tumors contained extramembranous alkaline phosphatase, localized as a continuous layer around the cells. Little 5''-nucleotidase activity was found. After 2 wk to 2 mo. in culture, extramembranous alkaline phosphatase activity was still present but in discrete foci only. In some cases the plasma membrane of a single cell was associated with reaction product and the adjacent cell was not. More often, however, certain areas of the plasma membrane within 1 cell were active and other areas were not. No corresponding structural differentiation could be seen.