Hormone‐sensitive adenylyl cyclase in preadipocytes cultured from adipose tissue: Comparison with 3T3‐L1 cells and adipocytes

The adenylyl cyclase system of preadipocytes derived from the stromal vascular fraction of perirenal rat fat pads was characterized. Unlike mature adipocytes, preadipocyte adenylyl cyclase was only weakly stimulated by catecholamines and adrenocorticotrophic hormone, but was stimulated by guanine nucleotides. Parathyroid hormone and 2‐chloroadenosine also stimulated preadipocyte adenylyl cyclase. The adenylyl cyclase system of preadipocytes resembled that of undifferentiated 3T3‐L1 cells. However, agents which induced the differentiation of the 3T3‐L1 cell adenylyl cyclase system did not have asimilar effect on predipocytes. A medium (CDM6) which induced some differentiation of preadipocyte adenylyl cyclase was developed. The observations that the adenylyl cyclase system of preadipocytes and undifferentiated 3T3‐L1 cells are similar, that preadipocyte adenylyl cyclase can be induced to develop along lines similar to early differentiation of 3T3‐L1 cells, and that the adenylyl cyclase system of fully‐differentiated 3T3‐L1 cells has characteristics intermediate between predipocytes and adipocytes, suggest that the differentiation of predipocyte and 3T3‐L1 adenylyl cyclase in vitro mimics adipose adenylyl cyclase development in vivo. The increased catecholamine and ACTH stimulation, and reduced GTP and adenosine sensitivites of adipocytes compared to preadipocytes suggest that a number of genes affecting adenylyl cyclase‐associated regulatory and receptor proteins are coordinately repressed and derepressed during development.