DISTRIBUTION OF PYY RECEPTORS IN HUMAN FAT-CELLS - AN ANTILIPOLYTIC SYSTEM ALONGSIDE THE ALPHA(2)-ADRENERGIC SYSTEM

The antilipolytic effect of peptide YY (PYY) and neuropeptide Y has recently been shown in human adipocytes. PYY receptors were investigated in three human adipose deposits. A greater number of I-125-labeled PYY binding sites was found in femoral adipocyte membranes (maximal binding = 40 +/- 4 fmol/mg protein; dissociation constant = 0.3 +/- 0.1 nM) when compared with mammary and pericolonic adipose tissue. PYY receptors, like alpha2-adrenergic sites, were largely expressed in femoral fat cells. Such a distribution was not specific either to inhibitory or to stimulating adenylyl cyclase systems since adenosine A1 and beta-adrenergic receptors were more numerous in pericolonic adipocytes. On isolated adipocytes, PYY (10(-7) M) inhibited lipolysis by 58 +/- 2% in femoral and 14 +/- 4% in pericolonic fat cells; epinephrine had the following similar response: 62 +/- 5 and 26 +/- 8%, respectively. A close relationship between the number Of alpha2-Sites and PYY sites and the antilipolytic effects initiated by PYY and an alpha2-agonist was observed. No significant differences were noted in the amount of G(i) proteins in femoral and pericolonic adipocyte membranes.