The cytoprotective effects of (+/-)-15-deoxy-16-alpha, beta-hydroxy-16-methyl PGE1 methyl ester (sc-29333) versus aspirin-shock gastric ulcerogenesis in the dog.

SC-29333 (SC) has been reported to protect the gastric mucosa from the effects of topical aspirin. We compared SC and 16,16-dimethyl PGE2 (16-dm) in 20 chambered canine stomachs (6 controls and 7 of each PG). Prostaglandin was added to an acid solution (100 mM HCl; 54 mM NaCl) at 0, .001, .01, 0.1, and 1.0 microgram/ml (two periods each). Then aspirin (20 mM) and PG (1.0 microgram/ml) (two periods) were followed by hemorrhagic shock (near 60 mm Hg mean arterial pressure). 16-dm caused a significant efflux of fluid (-6.5 +/- 5.3 to 17.3 +/- 6.7 microliters/min), Na+ (2.1 +/- 0.5 to 6.8 +/- 1.6 muEq/min), and Cl- (-0.9 +/- 2.4 to 5.3 +/- 1.3 muEq/min), but did not affect K+ or H+. 16-dm also caused a slight drop in potential difference (PD) (67.6 +/- 1.7 to 60.3 +/- 2.0 mV). 16-dm did not significantly affect total blood flow. Percent lesion formation was more severe than controls (20.2 +/- 3.5 vs 11.6 +/- 1.7 percent) but not statistically significant. SC had no significant effect on fluid, H+, Na+, K+, or Cl-. It caused an increase in blood flow (6.85 +/- 1.46 to 26.20 +/- 2.74 ml/min, p less than .001). SC significantly reduced percent lesion formation (1.9 +/- 0.9% p less than .001). We conclude: 1) SC causes an increase in mucosal blood flow and protects from aspirin-shock ulcerogenesis. 2) 16-dm stimulates an efflux of non-parietal extracellular fluid and fails to protect against aspirin injury during mucosal ischemia. 3) SC cytoprotection may be mediated by increased mucosal blood flow. 4) The mechanism of cytoprotection with 16-dm may require sufficient mucosal blood flow for filtration of non-acid fluid from blood to gastric lumen.