Localization and characterization of somatostatin-14 and somatostatin-28 receptors in the rat pituitary as studied by slide-mounted frozen sections.

The localization and characterization of somatostatin-14 (SS-14) and somatostatin-28 (SS-28) receptors were studied in the rat pituitary using the iodinated agonists [Tyr0, D-Trp8]-SS-14 and [Leu8, D-Trp22, Tyr25]-SS-28 as tracers. Slide-mounted frozen sections were used for the autoradiographic localization and biochemical characterization of somatostatin receptors. In the latter case, counting was performed on scraped off serial sections which contained both anterior and posterior pituitary. Specificity studies demonstrated that either tracer could be displaced with SS-28 and SS-14. A number of unrelated peptides were unable to compete with either tracer. Scatchard analysis of saturation curves gave one-site interactions with KD values of 0.53 +/- 0.08 nM and 0.22 +/- 0.03 nM for the SS-14 and SS-28 iodinated agonists, respectively. Using autoradiography, SS-14 and SS-28 receptors were shown to be distributed in the anterior pituitary only. Using densitometry, displacement and saturation curves could be also obtained.