HUMAN NEUROPEPTIDE YY1 RECEPTORS EXERT UNEQUAL CONTROL OF THE EXTRACELLULAR ACIDIFICATION RATE IN DIFFERENT

The ability of the human neuropeptide YY1 receptor subtype to increase the extracellular acidification rate in different cell lines was inve stigated by using the Cytosensor Microphysiometer. In CHO-Y-1 cells (C hinese Hamster Ovary cells expressing the cloned human neuropeptide YY 1 receptor), neuropeptide Y increased the acidification rate by up to 15% of the basal level with a -Log(EC50) of 7.42. As expected for neur opeptide YY1 receptors, this response was potently inhibited by the ne uropeptide YY1-selective non-peptide antagonist BIBP3226 nylacetyl)-N- [(4-hydroxy-phenyl)methyl]-D-arginine amide). Its enantiomer BIBP3435 etyl)-N-[(4-hydroxy-phenyl)methyl]-D-argininamide) was less potent. Th e antagonists themselves did not affect the extracellular acidificatio n rate at concentrations up to 10 mu M. In SK-N-MC cells (a neuroblast oma cell line of human origin that expresses the neuropeptide YY1 rece ptor) no change of the acidification rate could be observed in the pre sence of neuropeptide Y at concentrations up to 1 mu M. For control, t he neuropeptide YY1 receptors were also investigated by assessing whol e cell radioligand binding and, at the functional level, by assessing their ability to decrease the forskolin-induced accumulation of cAMP. The specific (i.e., neuropeptide Y-displaceable) binding of [H-3]neuro peptide Y was to a homogenous class of high-affinity sites in both SK- N-MC and CHO-Y-1 cells. The equilibrium dissociation constants for [H- 3]neuropeptide Y, the total number of binding sites and the kinetic co nstants for association and for dissociation were similar. Neuropeptid e Y produced a dose-dependent inhibition of forskolin-induced CAMP acc umulation in SK-N-MC cells (-log(EC50) = 9.40) but it did not affect C AMP accumulation in CHO-Y-1 cells. Non-transfected CHO-K1 cells were u sed as negative control throughout the study. No binding or response c ould be observed in these cells. Our data suggest that the signalling mechanisms of neuropeptide YY1 receptors are closely related to the ce ll type in which they are expressed. (C) 1998 Elsevier Science B.V.