Møldrup A, Billestrup N, Nielsen J H
Hagedorn Research Laboratory, Gentofte, Denmark.
J Biol Chem. 1990 May 25;265(15):8686-90.
Insulin-producing rat islet RIN-5AH tumor cells express multiple binding sites for human growth hormone (hGH). The effect of rat growth hormone (rGH), rat prolactin (rPRL), and human placental lactogen (hPL) on the binding of 125I-labeled hGH (125I-hGH) to RIN-5AH cells revealed the presence of both lactogen and somatogen receptor populations. Covalent cross-linking of 125I-hGH, 125I-rGH, and 125I-rPRL to the RIN cells identified a 115-kDa somatogen receptor protein that binds hGH and rGH but not rPRL and hPL, and a 95-kDa lactogen receptor protein that binds hGH, rPRL, and hPL but not rGH. Antiserum directed against the 37.5- and 40.7-kDa GH-binding proteins of mouse hepatic tissue specifically recognized the 115-kDa protein cross-linked with 125I-hGH, whereas a monoclonal antibody raised against the hepatic 42-kDa rPRL receptor recognized the 95-kDa protein cross-linked with 125I-hGH. Northern blot analysis of RNA from RIN-5AH cells using an rGH receptor-specific cDNA probe showed three transcripts of 5.8, 1.8, and 1.5 kilobases, respectively. Analysis with an rPRL receptor-specific cDNA probe revealed the presence of a predominant 3.5-kilobase transcript. We conclude that the insulin-producing cells express large forms of both the GH and PRL receptors which are structurally related to those of hepatic tissue.
