Butyrate-induced cell differentiation of cell-cycle mutants and ‘wild-type’ mastocytoma cells: Histamine, 5-hydroxytryptamine and metachromatic granules as independently regulated differentiation markers

Abstract

In cultures of heat-sensitive (hs; arrested at 39.5°C, multiplying at 33°C) and cold-sensitive (cs; arrested at 33°C, multiplying at 39.5°C) cell-cycle mutants that had been isolated from the same subclone (K21) of the murine P-815-X2 mastocytoma line, the degree of cell differentiation was assessed by determining the cellular histamine and 5-hydroxytryptamine (5-HT) content as well as the number of metachromatic granules per cell. The findings were compared with those obtained for ‘wild-type’ K21 and P-815-X2 cells. The addition of butyrate to ‘wild-type’ cells or to mutant cells maintained at the respective permissive temperature resulted in a relative increase in the level of all three differentiation markers. In cs mutant cells, essentially the same pronounced increase in granule numbers was observed during butyrate treatment at 39.5°C and during incubation at 33°C without butyrate, thereby suggesting that butyrate induces morphological cell differentiation in cs mutants via the same mechanisms as exposure to the nonpermissive temperature. In contrast, the histamine and 5-HT levels reached in hs and cs mutant cells in the presence of butyrate were higher than those observed during incubation at the nonpermissive temperature. Large quantitative differences were detected with respect to the potential of individual cell lines to express the three differentiation parameters. High levels of histamine were characteristic of‘wild-type’ P-815-X2 cells treated at 33°C with butyrate, while low amine levels and small numbers of granules were observed in K21 cells (i. e., the parent line of hs and cs mutants). In contrast, a high 5-HT content was typical of hs mutant cells treated with butyrate at 33° or 39.5°C, whereas high numbers of granules per cell were found after the exposure of cs mutant cells to butyrate and/ or the nonpermissive temperature. The quantitative expression of these differentiation parameters therefore appears to be independently regulated in hs and cs mastocytoma sublines.