Gastrin-releasing peptide (GRP) and its

Proforms of gastrointestinal peptides are cleaved at paired basic residues into intermediate forms. Paired basic residues at the C-terminal then are excised by carboxypeptidases before the peptide is amidated. An obese mouse, called Cpe(fat)/Cpe(fat), has a missense mutation in carboxypeptidase E (CPE) with no pancreatic CPE activity and a reduced processing of pancreatic proinsulin to insulin. The purpose of this study was 1) to look for the presence of CPE in the antrum of the stomach, duodenum, and colon in the Cpe(fat)/Cpe(fat) mouse; 2) to determine whether CPE is involved in the processing of progastrin (Pro-G) to its carboxyl-terminal amidated form; and 3) to determine whether a decrease in amidated gastrin results in an up-regulation of stomach gastrin messenger RNA (mRNA) levels. In Cpe(fat)/Cpe(fat) mice, CPE activity was absent in the antrum and colon. In Cpe(fat)/Cpe(fat) mice, amidated gastrin levels were reduced significantly. Levels of the precursor for amidated gastrin (gastrin-Gly-Arg-Arg) were markedly elevated. Gastrin mRNA levels were increased approximately 2-fold over the levels in Cpe(fat)/Cpe(fat) mice. These results indicate that CPE is needed for processing progastrin to gastrin in the stomach and that amidated gastrin exerts an inhibitory feedback effect on gastrin mRNA levels.

No abstract

The potential for the thiol-containing drugs, N-acetyl cysteine and N-mercaptopropionyl glycine, to act as antioxidants intracellularly has been studied in erythrocytes under oxidative stress. The effects have been compared with that of the glutathione peroxidase inhibitor, mercaptosuccinate. The results show differential responses of sickle and normal erythrocytes to the thiol compounds. N-acetyl cysteine is the more efficacious with no toxic effects in these systems. N-Mercaptopropionyl glycine is not only limited in its ability to demonstrate antioxidant capacity in erythrocytes but also exerts deleterious effects.

No abstract