Tissue distribution of growth hormone releasing hormone receptor

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The human growth hormone-releasing hormone (GHRH) is essential to the regulation of GH secretion and somatotroph proliferation. In 1992, molecular clonings of GHRH-receptor (GHRH-R) of human, rat and mouse were conducted. However, the expression of GHRH-R in human pituitary adenomas has been studied to only a limited extent by reverse-transcriptase-PCR (RT-PCR) and Northern blot analysis. This expression in human pituitary adenomas and non-neoplastic pituitary tissue apparently has not been examined by in situ hybridization histochemistry (ISH). The expression of human GHRH-R mRNA by RT-PCR and ISH was studied here not only in non-neoplastic pituitary tissue but pituitary adenomas as well. In all non-neoplastic pituitary specimens, this expression was recognized by RT-PCR.Only GH cells expressed GHRH-R mRNA,as indicated by in situ hybridization in the pituitary gland from a young girl. Among 38 pituitary adenomas, strong signals for GHRH-R mRNA were observed only in GH producing adenomas by RT-PCR and ISH.It is significant that no appreciable expression of GHRH-R was seen in the prolactin cells of normal pituitary gland, prolactinoma cells or cells from other types of adenomas.Based on the above, tumorigenesis or tumor growth of GH-producing cells would appear possibly related to the strong expression of GHRH-R mRNA.