Adenosine Release from Isolated Rat Adipocytes: Influence of Fat Cell Concentration and Cell Size 1

Abstract

The release of adenosine by isolated rat adipocytes into the incubation medium was studied in relation to fat cell size and concentration. Incubations were carried out for 60 min at 37°C in Krebs-Ringer bicarbonate-albumin medium containing 6 mM glucose. 2′-Deoxycoformycin was added to inhibit endogenous adenosine deaminase activity (maximal supression was achieved at 0.8 μM concentration of the inhibitor). The data show that (a) the amount of adenosine released into the medium was similar for the first and second 30-min incubation periods; (b) increasing adipocyte concentration markedly inhibited adenosine release; and (c) large fat cells (volume > 300 pl) released significantly more adenosine (per fat cell) into the medium than smaller fat cells (volume < 180 pl) when incubated at concentrations of ≥ 350,000 cells/ml. Above this cell concentration, differences between adenosine release and cell size were not noted. Adenosine release by isolated rat adipocytes appears to be a precisely regulated process which is exquisitly sensitive to the number of fat cells in the incubation medium and, to a certain extent, to the adipocyte size.