In situ hybridization study of growth hormone, prolactin, and proopiomelanocortin mRNAs in adenohypophyses of mice transgenic for human growth hormone.

Abstract

In mice transgenic for human growth hormone (GH) gene, pituitaries are significantly decreased in size and show morphologic changes in somatotrophs, lactotrophs, corticotrophs, and gonadotrophs that are due to the dual somatotropic and lactotropic effect exerted by the foreign hormone. To further elucidate the mechanisms by which GH, prolactin (PRL), and adrenocorticotropic hormone (ACTH) biosynthesis is regulated in this line of transgenic mice, we studied the pituitary content of GH, PRL, and proopiomelanocortin (POMC) mRNAs by in situ hybridization. Oligonucleotide probes labeled with35S were applied on paraffin sections of 7 pituitaries of transgenic mice (4 males and 3 females) and 7 pituitaries of sexmatched nontransgenic siblings. In both sexes, the number of cells and the intensity of hybridization signal for GH messenger RNA were decreased. In male mice, PRL mRNA was strongly diminished, whereas in female mice, no change was evident. The intensity of POMC mRNA signal was stronger in male transgenics than in the controls, The results suggest a decrease of GH gene transcription in both genders and of PRL gene only in males. In situ hybridization results are in accordance with previous immunocytochemical and ultrastructural findings describing inhibited somatotrophs in both sexes and suppressed lactotrophs in males.