EXPRESSION OF THE GENES ENCODING BOMBESIN-RELATED PEPTIDES AND THEIR RECEPTORS IN ANTERIOR-PITUITARY TISSUE

The bombesin-related peptides gastrin-releasing peptide (GRP) and neur omedin B (NMB) have been demonstrated in the anterior pituitary (AP) o n an immunological basis. We studied the presence of mRNAs for these p eptides and for their receptors by RNAse protection assay using fresh adult male rat AP, AP cell reaggregates cultured in the presence of es tradiol and the rat AP derived GH3 cell line. In total RNA from fresh AP we detected high amounts of NMB mRNA and much smaller amounts of GR P mRNA, while finding a weak signal for GRP-receptor (GRP-R) and NMB-r eceptor (NMB-R) mRNAs. In total RNA from the reaggregate cell cultures we detected high levels of NMB mRNA as well as a strong signal for GR P-R mRNA. Finally, in GH3 cells, high levels of NMB mRNA and GRP-R mRN A were found, while GRP mRNA and NMB-R mRNA remained undetectable even in high amounts (200 mu g) of total RNA. We conclude that mRNAs encod ing both bombesin-related peptides and each of the mRNAs encoding thei r receptors are expressed in rat AP tissue. NMB mRNA is more prominent than GRP mRNA in all AP-like tissues examined (fresh AP, estradiol-tr eated reaggregate AP cell cultures and GH3 eels). NMB-R mRNA and GRP-R mRNA are both present in low levels in fresh AP whereas the GRP-R mRN A is predominant in GH3 cells and estradiol treated AP reaggregate cel l cultures. Compared to fresh AP tissue, NMB mRNA and GRP-R mRNA expre ssion is enhanced in estradiol-treated reaggregate cell cultures. Thes e data suggest a local role for bombesin-related peptides in AP tissue .