Ubiquitous distribution of growth hormone receptors and/or binding proteins in adenohypophyseal tissue

Liver GH receptor (GHR)-like mRNA has been shown to be widely distributed throughout rat and rabbit pituitary glands. In the present study RNA extracted from rabbit anterior pituitary glands was reverse transcribed, and the cDNA amplified by the polymerase chain reaction (PCR) in the presence of 3'- and 5'-flanking oligonucleotide primers for the extracellular and transmembrane domains of the rabbit GHR. A 499-basepair (bp) fragment was generated, identical in size to that in rabbit liver, kidney, and adipose tissue. Digestion of this fragment with a restriction endonuclease (SalI) produced moieties of 280 and 219 bp, as observed for the amplified cDNA fragments from liver, kidney, and adipose tissue. In situ hybridization of a cRNA probe for the rabbit GHR with cryostat sections of the anterior pituitary gland was demonstrated. Specific hybridization occurred throughout the adenohypophysis and was present in somatotroph and nonsomatotroph cells, identified by hybridization of the same tissue sections with a complementary riboprobe for rat GH mRNA. Electron microscopy and immunogold staining, using monoclonal antibodies against the extracellular domain of the rat (MAb 263) or rabbit (MAb 7) GHR, demonstrated the presence of the...Continue Reading