Identification and tissue distribution of messenger RNA for the growth hormone receptor in the rabbit

Rabbit liver, a rich source of specific growth hormone (GH) receptors, contains three mRNA transcripts (4.2-4.5 kb, 3.1-3.2 kb, and 1.8-2.0 kb) which hybridize strongly to oligonucleotide probes complementary to nucleotide sequences in the extracellular and cytoplasmic regions of the rabbit liver GH receptor. The approximately 4.5 kb transcript was the most abundant and showed some sex difference (male greater than female) and a significant, approximately 2 fold increase in late pregnancy - observations consistent with changes seen in the specific 125I-hGH binding capacity of rabbit liver membranes prepared from the same tissue samples. The approximately 4.5 kb mRNA species, but not the smaller transcripts, was also detected, at lower abundance, in rabbit kidney, heart and lung but not in mammary gland, which is known to lack 125I-GH binding activity. These studies have identified the nature of the mRNA transcripts coding for the GH receptor in recognized/potential GH target tissues in the rabbit. The regulation of the major GH receptor mRNA in rabbit liver appears to broadly reflect known changes in expressed receptor protein.