Recently it has been shown that 3T3-L1 fibroblasts growing in culture can convert into adipose cells. This conversion is a type of differentiation which occurs after the cells form a monolayer and stop growing. Prostaglandin F2 alphaand 1-methyl-3-isobutyl xanthine trigger the differentiation process by rapidly and irreversibly programming the fibroblasts to differentiate into adipose cells within 8 days. The proposed research involves further studies of this interesting phenomen in the hopes of gaining insight at the molecular level of the differentiation process. To determine if the triggering of differentiation is a general phenomenon, a number of cell types will be investigated using epinephrine, and ACTH in any cells that exhibit the conversion into adipocytes. Triglyceride formation is measured by Oil-Red-O staining and radioactive labeling of lipids. Prostaglandin binding, subcellular distribution, specificity and the effect of indomethacin on the conversion process will be studied. The role of the cyclic nucleotides in the triggering of differentiation will also be investigated with emphasis on the enzymes involved in cyclic nucleotide metabolism.