Determination of guanine nucleotide sensitivity of [125-I]-neuropeptide Y binding in the rat pituitary gland by quantitative autoradiography.

[125I]-neuropeptide Y receptors were characterized in the rat pituitary gland using quantitative autoradiography. Scatchard analysis of saturation isotherms showed high affinity (Kd 8.5 x 10(-11) M) and single class of binding sites (Bmax 0.22 pmol/mg of protein) in the posterior lobe of the pituitary gland, with no specific binding in the intermediate or anterior lobe. Increasing concentrations of guanine nucleotide analogues and peptide YY inhibited neuropeptide Y binding. In addition, neuropeptide Y binding was pertussis-toxin-sensitive. These results add additional information about a possible neuronal (through neuropeptide Y) and hormonal (through peptide YY) regulation of posterior pituitary function, which is most probably GTP-dependent.