Pharmacological regulation of gastric mucous glycoprotein secretion

Gastric mucous glycoproteins (GMGs) are an important protective component of the gastric 'mucus bicarbonate barrier'. The characterization of drug effects on GMG metabolism is difficult because the quantification of GMGs poses analytical problems and because indirect drug effects (e.g. on other gastric secretory functions) can influence GMG metabolism or quantification and thereby complicate the interpretation of in-vivo experiments. The use of suitable in-vitro systems, in particular of isolated gastric mucous cells, helped to resolve the latter problem and enabled the characterization of direct effects of prostaglandins, gastric acid secretagogues, peptide hormones, growth factors, adrenoceptor agonists, and synthetic compounds (e.g. teprenone) on GMG metabolism. Furthermore, from these experiments, evidence has accumulated that the cyclic AMP system, the inositol trisphosphate/calcium/protein kinase C system and the cyclic GMP system are involved in the intracellular transmission of drug effects on GMG metabolism.