NEUROPEPTIDE-Y RECEPTORS IN A PROTOZOA STYLONYCHIA-MYTILUS

Radio ligand binding assays(RLBA) were used to study neuropeptide Y (N PY) receptors in a protozoa Stylonychia mytilus. The experimental resu lts showed that 2-3 x 10(3)/mL Stylonychia cells incubated in Pringshe im solution which contained H-3-NPY could specifically bind H-3-NPY an d concomitantly present saturable characteristic. This suggested that Stylonychia possessed some specific binding sites for NPY. Scatchard t ransformations of binding assay for the NPY receptors at 25 degrees C are compatible with the specific activity of 42. 47 fmol/10(3) cells a nd the binding equilibrium constant of 0.113 nmol/L. The data of I-125 -NPY binding assay to the membrane protein extract of Stylonychia indi cated that there was a significant difference between the amount of to tal bound and nonspecific bound of I-125-NPY. This result indicated th at NPY receptors were probably localized mainly on the cell membrane.