Prolactin binding sites in the adrenal glands of mink (Mustela vison)

1. The purpose of this study was to determine if the mink adrenal gland might be a target organ for prolactin by establishing whether or not binding sites for the hormone exist in adrenal cell membranes. 2. Adrenal glands were collected from adult female mink in November, 1991, homogenized and subjected to differential centrifugation into three particulate fractions; 1500, 15,000 and 50,000 g. All binding determinations were made using 125I-oPRL and 200-300 micrograms protein from the 50,000 g particulate fraction. Optimal binding occurred within 8 hr at 25 degrees C. 3. Scatchard analysis of saturation data revealed a single set of high affinity (Kd = 9.27 x 10(-11) +/- 1.63 M), low capacity (Bmax = 34.22 +/- 5.37 fmol/mg) binding sites. 4. Binding sites appeared to be hormone specific as only oPRL (73% displacement) and oLH (8% displacement) inhibited binding of 125I-oPRL to adrenal membranes. No inhibition of 125I-oPRL binding to adrenal membranes occurred in the presence of a 500-fold excess of bTSH, oGH or oFSH. 5. Prolactin binding sites were readily detected in adrenal and kidney tissue, but were low in liver and almost non-detectable in spleen or lung tissue. 6. Our data suggest that the mink adrenal gland is a target organ for prolactin and that an interaction between the pituitary and adrenal glands may exist that is important for the regulation of such physiological processes as fur growth cycles.