Partial purification of somatotropin receptors from pig liver: they arise from a single somatotropin receptor messenger RNA transcript.

I. Louveau, T. D. Etherton

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Specific binding sites for porcine somatotropin (pST) have been identified in pig liver microsomal membranes. Little information, however, is available about the size and number of ST receptor (ST-R) forms present. Therefore, the present study was conducted to characterize ST-R in pig liver using two approaches. In the first set of experiments, cross-linking of [125I]bST (bovine ST) to microsomal membranes, followed by gel electrophoresis under reducing conditions, revealed the presence of a predominant protein of 107 kDa and four other proteins of 71, 52, 40, and 26 kDa. In a second set of experiments, ST-R were partially purified using affinity chromatography. Binding studies indicated that there was an approximately 1,800-fold purification compared to liver homogenate. Two specific proteins of 107 and 40 kDa were detected after crosslinking of [125I]bST to partially purified ST-R. Northern blot analysis revealed that these proteins arise by posttranslational modification of a single 4.2-kilobase somatotropin receptor messenger RNA transcript. Although the present study indicates that several forms of ST-R are present in pig liver, it is not clear what physiological role these different ST-R play in mediating the hepatic effects of pST. It is evident, however, that the smaller proteins are generated from the 107-kDa protein, which is the predominant isoform present in liver microsomal membranes.

Original languageEnglish (US)
Pages (from-to)3421-3428
Number of pages8
JournalJournal of animal science
Issue number11
Publication statusPublished - Nov 1992


All Science Journal Classification (ASJC) codes

  • Food Science
  • Animal Science and Zoology
  • Genetics

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