DIFFERENTIAL EXPRESSION AND REGULATION OF SSTR(2) MESSENGER-RNA IN RAT GASTRIC ANTRUM AND CORPUS

Somatostatin modulates both endocrine and exocrine functions in the ga stric mucosa, where three of the five cloned somatostatin receptors ar e present. This study examines changes in somatostatin receptor (SSTR) mRNA abundance during fasting, feeding, and profound acid inhibition with omeprazole. Serum gastrin as well as somatostatin and SSTR mRNA a bundances were measured in antrum and corpus. In Northern blots of cor pus RNA, the SSTR(2) probe hybridized with two previously reported spe cies of mRNA (2.4 and 2.8 kb); in addition, a weak previously unreport ed 1.6-kb band was detected. In antrum, the 1.6-kb band dominated. Fas ting increased antral somatostatin mRNA from 100 +/- 8 to 161 +/- 24% and SSTR mRNA from 100 +/- 10 to 179 +/- 14% (P < 0.05). Omeprazole re duced antral somatostatin mRNA to 34 +/- 4% of control (P < 0.05) and elevated SSTR mRNA to 135 +/- 5% of control (P < 0.01). Omeprazole tre atment reduced corpus somatostatin mRNA to 59 +/- 5% (P < 0.05), and e levated SSTR mRNA to 140 +/- 3% of control (P < 0.01). The results the refore indicate that a novel SSTR mRNA subtype exists in the stomach a nd predominates in the antrum. The abundance of this SSTR mRNA is upre gulated by both fasting and achlorhydria; conditions that increase or decrease endogenous antral somatostatin, respectively.