Figure 4.

(Left) Binding of ¹²⁵I-10 to sections containing sst₁-sst₅-expressing cell pellets. All sections were incubated with 8,000 cpm/100 μl of ligand. Strong specific labeling with the ligand is seen only in sst₃ cells. (A, C, E, G, I) Autoradiograms showing total binding of ¹²⁵I-10 to sections of cell pellets expressing sst₁ (A), sst₂ (C), sst₃ (E), sst₄ (G), and sst₅ (I). (B, D, F, H, K) Autoradiograms showing nonspecific binding of ¹²⁵I-10 (in the presence of 10⁻⁶ M unlabeled 10). (Right) In vitro receptor autoradiography detection of sst₃ receptors in a human inactive pituitary adenoma. (A) Hematoxylin and eosin-stained section. Bar = 1 mm. (B) Autoradiogram showing total binding of ¹²⁵I-labeled 10. (C) Autoradiogram showing nonspecific binding of ¹²⁵I-10 (in the presence of 10⁻⁶ M unlabeled 10). The tumor was shown to have predominantly and abundantly sst₃ mRNA with in situ hybridization. Although a significant nonspecific binding is seen in C, specific binding can nevertheless be clearly identified.