Conversion to adipocytes of a clonal bone marrow preadipocyte line (H-1/A) and fatty acid composition of the resultant adipocytes.

Conversion to adipocytes and fatty acid composition were investigated in a clonal bone marrow preadipocyte line (H-1/A). The growing cells exhibited a fibroblastic appearance. After the cessation of growth, triacylglyceride (TG) synthesis in the cells increased as they incorporated precursor from the growth medium and became adipocytes. Hydrocortisone and insulin accelerated the TG synthesis in H-1/A cells in a dose-dependent manner when they were cultured in the growth medium containing 10% horse serum. The rate of conversion to adipocytes was reduced as the concentration of horse serum was decreased, and this reduction was not influenced by the addition of insulin and/or hydrocortisone. These results suggest that conversion to adipocytes of H-1/A cells is primarily dependent on some component(s) of the serum. Conversion to adipocytes of the cells may involve a process of differentiation since the conversion was completely inhibited when the cells were cultured in the presence of bromodeoxyuridine. Fatty acid composition was significantly different between adipose H-1/A cells and adipocytes derived from other marrow preadipocyte line MC3T3-G2/PA6 cells. Unsaturated fatty acids accounted for 76% of the fatty acid composition of adipose H-1/A cells; in contrast, saturated fatty acids constituted 65% of the fatty acid composition of the adipose MC3T3-G2/PA6 cells. These results suggest that there is a heterogeneity of preadipocytes in bone marrow. These two preadipocyte lines thus provide a useful tool for the study of marrow adipocytes and can also be used to analyze the hematopoietic microenvironment through studies of the effect of these cells on hematopoietic cell proliferation.