In vivo study of platelet aggregation in rats.

A simple in vivo method for the study of platelet aggregation in rats is described. The presence of circulating platelet aggregates in the blood of rats is shown after induction of intravascular platelet aggregation. This aggregation can be triggered either acutely, for example with ADP and collagen, or chronically, for example with a thrombogenic diet. The antagonist activity of acetylsalicylic acid indicates that this method can be used to evaluate anti-thrombotic drugs.

Inhibition of potassium-induced contracture of the isolated rat aorta by amiloride.

Potassium contractures of helically cut strips of rat aorta were recorded isometrically. Contractures induced by KCl 40 mmol/l were decreased dose-dependently by amiloride (1.7 X 10(-5) to 1.4 X 10(-4) mol/l) added to the bath 10 min before the depolarization. Ouabain (10(-3) mol/l) antagonized this effect. Contractures induced by using, instead of normal Krebs solution, a solution in which potassium was replaced by sodium (Krebs potassium) were also decreased dose-dependently by amiloride, but the slope of the linear log dose-effect curve line was steeper. When arteries were incubated in a solution deprived of sodium and calcium (isotonicity maintained by choline), the intensity of consecutive contractures by Krebs potassium decreased progressively. Incubation in a normal Krebs solution restored the normal contractures; amiloride added at the same time prevented this restoration. These findings are in agreement with the assumption that sodium-calcium exchange plays an important part in the contracture of vascular smooth muscles.

Alternative methods: Hen's egg chorioallantoic membrane and in vitro cytotoxicity - a complementary approach.

Synopsis The ocular irritation potential of 107 cosmetics and toiletries was compared using the rabbit's eye Draize test (IOMA), a cytotoxicity in vitro method (CFIO), and the hen's egg chorioallantoic membrane test (HET-CAM). There was a good correlation between both alternative methods and the Draize test. Non-correlating results were observed in 12 cases with the HET-CAM method (six false positives, two false negatives, four technical failures) and in 14 cases with the CFIO method (ten false positives, four false negatives). However, all clearly irritant products were detected. False negatives were only found in products whose ocular irritation index lay close to the boundary (IOMA = 15) between the slightly and the moderately irritant products. None of the products was falsely found to be negative by both alternative methods. Therefore, the risk of underestimating the ocular irritation potential was avoided. The coupling of these two methods seemed to be of interest as an alternative approach to the assessment of the potential for ocular irritation of cosmetics and toiletries.