Influence of anatomic site and age on the replication and differentiation of rat adipocyte precursors in culture

of adipocyte precursors from 70-400-g rats, we ex-plored the possibility that regional variations in prop-erties of adipose tissue may reflect site-specific char-acteristics intrinsic to the cells, rather than extracel-lular influences. Initially, studies were made of the nature of the fibroblastlike cells from perirenal adipose tissue stroma. Using colony-forming techniques, it was shown that these cells were adipocyte precursors; each confluent colony that was derived from a single cell displayed differentiated adipocytes. This characteristic was evident in cells from rats of all ages and persisted during secondary culture. At all ages of rats studied, perirenal cells replicated more rapidly than epididy-mal precursors, e.g., for 179-g rats the population-dou-bling times were 19.3±0.7 vs. 25.5±1.2 h (means±SEM, P < 0.03). With aging of the rats, the replication rate of their perirenal cells decreased progressively. Under clonal conditions, the colony size distribution of both perirenal and epididymal precursors revealed heter-ogeneity in their capacity for replication, perirenal cells showing greater proliferation. These also differ-entiated more extensively by morphologic and enzy-matic criteria. Age and site had effects that persisted through many cell generations; however, high-fat feeding had no perpetuating influence. The dissimilar properties of perirenal as compared with epididymal precursors may reflect differences in regulation of gene expression. The data are also compatible with a later development in embryological life of perirenal tissue. Dr. Djian was a Fellow of the Banting and Best Diabete