Different metabolic regulation by adenosine in omental and subcutaneous adipose tissue

Adenosine content was higher in omental adipose tissue (0.91 +/- 0.13 nmol g-1 of wet weight; mean +/- S.E.M.) than in abdominal subcutaneous adipose tissue (0.42 +/- 0.08 nmol g-1 of wet weight) in rapidly frozen surgical biopsy samples taken from ten patients undergoing elective abdominal surgery. This difference was statistically significant (P less than 0.002). The sensitivity of isoprenaline-stimulated lipolysis to inhibition by N6-(phenylisopropyl)adenosine was studied in omental and abdominal subcutaneous adipocytes isolated from nine patients. The effect of this adenosine Ri-site agonist was less pronounced in omental than in abdominal subcutaneous adipocytes which could be due to a desensitization phenomenon. This difference was statistically significant (P = 0.012). The ratio of the inhibitory guanine nucleotide binding proteins Gi1 and Gi2 to the corresponding stimulatory protein Gs was the same in plasma membranes prepared from omental and abdominal subcutaneous adipocytes. In conclusion, in omental adipose tissue, adenosine content is higher and the response to this nucleoside is less pronounced than in subcutaneous adipocytes. This difference cannot be explained by a different (Gi1 + Gi2)/Gs ratio.