Electron microscopic observations comparing the gastric mucosal damage induced in rats and pigs by benoxaprofen and aspirin, reflecting their differing actions as prostaglandin-synthesis-inhibitors.

The ultrastructural changes in the gastric mucosa induced by oral administration of aspirin (2 x 125 mg/kg/day) were compared with the effects of benoxaprofen (20 mg/kg/day) in pigs and normal and arthritic rats after 10 or 14 days' treatment respectively. The object was to compare the effects of drugs having different effects on prostaglandin-synthesizing systems on the development of gastric mucosal damage. Benoxaprofen caused less gastric damage than aspirin. There were fewer lesions in benoxaprofen-treated animals and those which were seen were much less extensive. There were qualitative similarities between the effects of the drug treatments. There were also differences in the mucosal changes produced by both drugs in pigs and rats. This included (1) extravasation of erythrocytes which was seen in rats but not pigs, and (2) interstitial changes also seen in rats but not pigs. These interspecies variations may be due to differences in the resistance of the capillaries to drug effects. There were no differences in the mucosal-cell damage seen in normal compared with arthritic rats.

A modification of the adenosine triphosphatase method to demonstrate epidermal Langerhans cells.

Epidermal Langerhans cells are most commonly demonstrated by utilizing their adenosine triphosphatase reactivity. Although this is one of the best methods available to the light microscopist, it is a capricious technique which does not always permit optimal demonstration of this cell population. Prolonged fixation in cacodylate formalin and incubation in 1.32 X 10-3 molar adenosine triphosphatase permits reliable reproduction and good definition of these dendritic cells.

Ultrastructural observations on the pathogenesis of aspirin-induced gastric erosions.

It is shown by transmission electron-microscopy that the first structural change in rats, following a dose of aspirin, is to the basement membrane of the endothelial cell of the capillary and post-capillary venule. This leads to the breakdown of small blood vessels before any other cytolytic effect. This is a focal effect and it is proposed that the erosion develops as an ischaemic infarct.