Search

Nocloprost (9 beta-chloro-16,16-dimethyl prostaglandin E2 (PGE2)) was examined for gastroprotective and ulcer-healing activity and compared to 16,16-dimethyl PGE2 (dmPGE) in rats. Nocloprost given intragastrically (i.g.) at various doses (0.01-10 micrograms/kg) 30 min before 100% ethanol, acidified aspirin (ASA), acidified taurocholate, water immersion, or restraint stress dose dependently prevented the formation of gastric lesions, the ID50 values being 0.25, 0.58, 0.06 and 0.12 micrograms/kg, respectively. The gastroprotection provided by nocloprost given i.g. was somewhat enhanced by the presence of acid in the stomach and was reduced by inhibition of gastric acid secretion. Nocloprost given s.c. also showed protective activity against ethanol damage but was ineffective when applied intraduodenally. The protective effect of nocloprost lasted about 8 h whereas that induced by dmPGE lasted 6 h. Nocloprost (0.01-100 micrograms/kg) given i.g. failed to affect gastric acid secretion or intestinal secretion (enteropooling) but prevented the increased gastroduodenal alkaline secretion. Nocloprost alone caused only a transient increase in the mucosal blood flow but prevented the fall in blood flow caused by 100% ethanol. [3H]Nocloprost was absorbed from the small intestine but was then taken up and metabolized by the liver and excreted into the bile so that very little reached the systemic circulation in an unchanged form. Nocloprost, unlike dmPGE, accelerated the healing of chronic gastric ulcerations and enhanced mucosal growth. We conclude that nocloprost is a locally active PGE2 analog with high cytoprotective and ulcer-healing efficacy.

Leukotriene C4 (LTC4) and platelet activating-factor (PAF) were found to affect gastric microcirculation and mucosal integrity but their role in acute gastric damage has not been established. The present study with rats confirms that exogenous LTC4 (10 micrograms/kg.h s.c.) or PAF (10 micrograms/kg i.p.) alone caused only mild gastric mucosal injury but greatly augmented mucosal lesions produced by other irritants such as absolute ethanol, taurocholate, aspirin or stress. These acute lesions were accompanied by a significant increase in mucosal generation of LTC4, and the addition of PAF further increased it. Pretreatment with BN 52021, a PAF receptor antagonist, abolished PAF-induced gastric lesions and reduced LTC4 generation in tests with PAF plus ethanol. Nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway, and FPL 55712, an LTC receptor-antagonist, reduced dose dependently the extent of gastric damage in various models of gastric lesions. Again, these protective effects were accompanied by a reduction in mucosal LTC4 formation. In addition, the protection induced by nordihydroguaiaretic acid was reversed in part by the pretreatment with indomethacin, suggesting that it could be attributed to increased biosynthesis of protective PG. The results indicated that LTC4 biosynthesis is increased in various forms of gastric damage and that LTC4 may be involved in the pathogenesis of this damage.