EXPRESSION OF THE GROWTH-HORMONE RECEPTOR GENE IN HUMAN DIGESTIVE TISSUES

We have examined the forms and the distribution of the messenger ribon ucleic acids (mRNAs) encoding the GH receptor (GHR) in human digestive tissues. GHR mRNAs were identified and characterized by Northern blot , dot blot, and in situ hybridization analyses, using complementary DN As coding for the extracellular part of the human liver GHR. Amplifica tion using the polymerase chain reaction was also used, as tissues exp ress low levels of GHR mRNAs. Our results demonstrate that the GHR gen e is expressed in human liver, pancreas, esophagus, stomach, small int estine, and colon. A single 4.5-kilobase mRNA form, which probably enc odes the full-length membrane receptor, was detected. GHR mRNA was vis ualized by in situ hybridization in hepatocytes, exocrine pancreas, an d some islet cells; signal was also present in the mucosa of the diges tive tract. No specific GH-binding-protein mRNA was found, suggesting that in man, the soluble form of the receptor is generated through pro teolytic cleavage of the membrane receptor.