Identification of alternatively spliced messenger ribonucleic acid encoding truncated growth hormone-releasing hormone receptor in human pituitary adenomas

The expression of GHRH receptor (GHRH-R) messenger ribonucleic acid (mRNA) was studied in 22 pituitary adenomas and 2 normal anterior pituitaries. Northern blot analysis revealed that GHRH-R mRNA were expressed in all 14 GH-producing adenomas, 1 of 3 ACTH-producing adenomas, the 1 PRL-producing adenoma, 2 of 4 nonfunctioning adenomas, and the 2 normal anterior pituitaries. Their expression levels varied among GH-producing adenomas and were relatively low in GH-nonproducing adenomas. In addition to the major transcript with a molecular mass of 2.0 kilobases (kb), the transcripts were identified at 2.8 and 4.5 kb in some GH-producing adenomas. To examine the structural variations in GHRH-R mRNA in pituitary adenomas, we amplified the complementary DNA fragment encompassing the region from the third cytoplasmic loop to the sixth transmembrane domain of GHRH-R. This region was selected because this region of the G protein-coupled receptor has been known to interact with G protein. Two amplified fragments with...