iloprost and Stomach-Ulcer

In this study, the time-dependent ulcerogenic effects of restraint-cold stress and indomethacin on the gastric mucosa and the temporal variation in the protective effect of iloprost, a synthetic stable analog of prostacyclin, were investigated in rats synchronized to 12h light and 12h darkness, lights on at 08:00. The severity of gastric ulceration produced by either stress or indomethacin showed marked circadian variation; it was greatest at 11 HALO (hours after lights on) for restraint-cold stress and at 23 HALO for indomethacin. The severity of the induced ulcerogenesis was least at 7 HALO for both stimuli. The protective effect of iloprost against restraint-cold stress was most prominent at 15 HALO and 19 HALO with an approximately 80% protection score. On the other hand, pretreatment with iloprost reduced the indomethacin-induced mucosal injury only at 23 HALO. The circadian variation in the effect of iloprost and in the rhythmic modalities of these two experimental ulcer models are indicative of differences in their underlying mechanisms. In experimental models of ulceration, the circadian time of application of the ulcerogenic stimulus must be considered as an important experimental factor. Moreover, the protective effectiveness of antiulcer drugs can express time-dependent differences and must also be taken into account in investigative research.

Topics: Animals; Anti-Ulcer Agents; Circadian Rhythm; Cold Temperature; Disease Models, Animal; Drug Administration Schedule; Female; Gastric Mucosa; Iloprost; Indomethacin; Male; Rats; Restraint, Physical; Stomach Ulcer; Stress, Physiological

Infusion of endothelin-1 reduced vascular flow in the isolated perfused rat stomach. Concurrent infusion of iloprost and capsaicin, respectively, did not counteract the flow-reduction caused by endothelin-1. Infusion of prostaglandin (PG)F2 alpha caused vasoconstriction and significantly augmented the endothelin-1-induced flow reduction. In vivo, i.v. infusion of endothelin-1 (50 pmol/kg//min for 10 min) did not cause gastric mucosal damage, but enhanced injury produced by intragastric instillation of 20% ethanol. Intragastric administration of iloprost or PGF2 alpha prevented the pro-ulcerogenic effect of endothelin-1. Similarly, stimulation of afferent sensory neurons by intragastric capsaicin (0.5 mg/kg) protected against damage caused by endothelin-1 and 20% ethanol. Functional ablation of afferent sensory neurons by s.c. administration of 125 mg/kg capsaicin markedly enhanced gastric mucosal damage by intraluminal 20% ethanol. This damage was, however, not further increased by infusion of endothelin-1. These findings show that protection against the proulcerogenic effect of endothelin-1 can occur without antagonism of vasoconstriction. The findings also show that parameters involved in protection such as afferent sensory neurons do not contribute to the pro-ulcerogenic effects of endothelin-1 suggesting that protection against and potentiation of damage rely on different mechanisms.

Topics: Animals; Capsaicin; Dinoprost; Endothelins; Gastric Mucosa; Iloprost; In Vitro Techniques; Neurons, Afferent; Prostaglandins; Rats; Regional Blood Flow; Stomach; Stomach Ulcer; Vasoconstriction

1. The interactions between carbenoxolone and nitric oxide (NO) were examined by investigating their effects on human platelet aggregation, on rat aortic strips precontracted by phenylephrine and on protection of rat gastric mucosa against ethanol-induced injury. 2. Carbenoxolone (100-300 microM) caused a significant and concentration-dependent potentiation of rat peritoneal neutrophil (RPN)- 3-morpholino-syndnonimine (SIN-1)- or iloprost-induced inhibition of platelet aggregation. Higher concentrations (500 microM) of carbenoxolone alone markedly inhibited platelet aggregation. Pretreatment with carbenoxolone (100-300 microM) antagonized the reversal of the RPN- or SIN-1-induced antiaggregatory effect by oxyhaemoglobin (10 microM). 3. Rat aortic strips with intact endothelium precontracted by phenylephrine (0.1-0.3 microM) were relaxed by carbenoxolone (100-300 microM) in a concentration-dependent manner. Relaxations were abolished by mechanical removal of the endothelium or by incubation with methylene blue (10 microM) or NG-nitro-L-arginine (L-NNA, 100 microM). Sodium nitroprusside (10 nM)-induced relaxations of endothelium-denuded rat aortic strips were potentiated by carbenoxolone (100 microM). . The carbenoxolone (200 mg kg-1, p.o.)-induced gastroprotection against ethanol was antagonized by L-NNA (5-40 mg kg-1) in a dose-dependent manner. Pretreatment of rats with indomethacin (10 mg kg-1, s.c.) increased the effect of L-NNA. 5. The results suggest that the activity of carbenoxolone in the experimental systems tested is due to phosphodiesterase inhibition, although radical scavenging properties of the drug could contribute to some of the effects observed. In the rat gastric mucosa both increased prostaglandin levels and effects on the NO system could contribute to the protective action of carbenoxolone.

Topics: Animals; Aorta; Arginine; Carbenoxolone; Gastric Mucosa; Humans; Iloprost; In Vitro Techniques; Male; Methylene Blue; Molsidomine; Muscle Relaxation; Muscle Tonus; Neutrophils; Nitric Oxide; Nitroarginine; Nitroprusside; Oxyhemoglobins; Rats; Rats, Inbred Strains; Stomach Ulcer; Vasodilator Agents

This study was undertaken to evaluate the efficacy of iloprost and UK 38485 in the prevention of gastric lesions due to restraint-cold stress, ethanol or indomethacin. Prior injection of iloprost to the rats significantly prevented the increase in ulcer index by restraint- cold stress or indomethacin but nonsignificantly reduced the ulcer index induced by ethanol. UK 38 485 at lower doses caused a highly significant decrease in the ulcer index induced by all noxious stimuli used in this study. UK 38 485 also reduced the increased 3H back diffusion due to restraint-cold stress. Higher doses of the compound, however, failed to decrease the mucosal damage due to restraint-cold stress. Combination of iloprost and UK 38 485 produced a further significant decrease in the ulcer index induced by all noxious stimuli and increased 3H back diffusion induced by restraint-cold stress. In relation to these results the importance of PGI2/TXA2 ratio in the production of gastric mucosal lesions is discussed.

Topics: Animals; Epoprostenol; Ethanol; Female; Gastric Mucosa; Iloprost; Imidazoles; Indomethacin; Male; Rats; Stomach Ulcer; Stress, Physiological; Thromboxane A2; Thromboxane-A Synthase

A new synthetic stable analog of prostacyclin (ZK 36 374, Iloprost) has been shown to inhibit gastric lesions due to restraint-cold stress in rats in a dose-dependent manner. Therefore substitution of the decreased prostacyclin in the gastric mucosa may play an important role in the prevention or treatment of gastric ulcers.

Topics: Animals; Cold Temperature; Dose-Response Relationship, Drug; Epoprostenol; Female; Gastric Mucosa; Iloprost; Injections, Intraperitoneal; Male; Rats; Rats, Inbred Strains; Stomach Ulcer