Characterization of Union Sites for Opioids in Human Lymphocyte Membranes | Biomedgrid

The opioid peptides Methionine enkephalin and β-Endorphin are stimulators of Natural Killer cytolytic activity. To know the biochemical mech-anisms that explain this action, the binding of Methionine enkephalin and Naloxone in presence or ausence of Na+ ion and GTP to human Lymphocyte membranes was characterized.Methionine enkephalin or β-Endorphin in concentrations greater than physiological concentrations delivers stimulations of the order of 25% on the respective control value. For the receptors, a binding assay of the radioligands (3H)-Methionine enkephalin and (3H)-Naloxone was used, with the Scatchard analysis finding only one type of binding site in each case, with KD values of 6.8 and 5.9 [nm] and Bmax of 38 and 54 [fmol/mg of protein] respectively. These values are not comparable to those described in nervous, tumor or lymphoid tissue. The displacement tests revealed similarity between Naloxone and Methionine enkephalin binding sites due to their mutual displacement, unlike that observed with β-Endorphin.In contrast to previous studies, it was found that the effect of the Na+ ion (100 mM) did not modify the IC50 values, whereas GTP markedly reduced the total binding of both ligands: Methionine enkephalin and Naloxone and suggests the participation of a protein with G protein charac-teristics.