The rat as a model to evaluate the gastric irritation potential of alkaline products.

Animal models historically used to assess the acute gastric irritation potential of accidental ingestion of consumer products include the dog, pig, rabbit, and cat. In looking at alternative methods that are of shorter duration and more cost-effective, the rat is being evaluated as a potential model. Acute gastric irritation is known to increase as the reserve alkalinity of the formulation increases. In initial experiments to assess the rat as a potential model, animals were dosed via oral gavage with 1 of 4 formulations ranging in reserve alkalinity from 4.0 to 10.8. Necropsies were performed at 15 and 60 min after dosing. Macroscopic and microscopic evaluations of the stomach revealed morphological differences in the various treatment groups that distinguish granular formulations having either a low (R.A. = 4.0), moderate (R.A. = 7.1), or higher (R.A. = 10.8) reserve alkalinity. Additionally, it was observed that the acute gastric changes in rats dosed with a liquid formulation having a low (R.A. = 4.2) reserve alkalinity were similar to those in rats dosed with a granular formulation having a moderate reserve alkalinity (R.A. = 7.1). This suggests that other factors such as types of ingredients, pH, and physical form influence the extent of acute gastric irritation and demonstrates that an evaluation of only reserve alkalinity is not sufficient to ensure the safety of these products. This preliminary work supports the rat as a potential model to assess the acute gastric irritation potential of alkaline formulations or substances.

Spontaneous corneal dystrophy and generalized basement membrane changes in Fischer-344 rats.

Groups of young, sexually mature Fischer-344 rats (n = 25/sex) obtained from commercial breeders were examined ophthalmologically and histopathologically to determine the prevalence and severity of corneal basement membrane lesions (corneal dystrophy) and basement membrane changes in select nonocular tissues. Results disclosed a high incidence of corneal basement membrane dystrophy in rats of both sexes from all breeders; however, severity levels were significantly increased in rats obtained from one breeder when compared to others. Furthermore, rats that displayed the most advanced corneal lesions also exhibited more severe basement membrane changes in other organs, especially renal tubules and vascular internal laminae. These findings suggest that both ocular and nonocular dystrophic changes may have been linked through common physiologic (or genetic) mechanisms. Animals that displayed basement membrane lesions were not considered to represent compromised biologic test systems.

Chlorphentermine suppresses the phosphatidylinositol pathway in concanavalin A-activated mouse splenic lymphocytes.

We have previously demonstrated that the chlorphentermine (CP)1-induced impairment in lymphocyte blastogenesis involves drug-induced inhibition of an event which occurs very early during lymphocyte activation. An early event, which is associated with mitogen-induced lymphocyte activation, involves the hydrolysis of phosphatidylinositol by phospholipase C to yield inositol phosphates and diacylglycerol as products. Inositol phosphates and diacylglycerol then function as mediators of a trans-membrane signal for the continuation of the cellular response. It was the purpose of the present study to determine the effects of CP on this phosphatidylinositol pathway. We demonstrated that formation of inositol phosphates in lymphocytes increases progressively above control over a 2 hour period following concanavalin A (Con A)-stimulation. In contrast, lymphocytes pre-incubated with 10(-5)M CP for 60 min, then stimulated with Con A for 2 hours in the presence of 10(-5)M CP, exhibit a significantly depressed inositol phosphate formation. In addition, CP also inhibited the activity of phospholipase C (IC50 = 0.58 mM), the enzyme responsible for the formation of inositol phosphates during lymphocyte activation. Further, lymphocytes activated in a manner that bypasses the phosphatidylinositol pathway are not inhibited by 10(-7)M or 10(-9)M CP as are cells activated with Con A. These results suggest that the suppression of the phosphatidylinositol pathway may be involved in the inhibition by CP of lymphocyte blastogenesis induced by Con A.

Morphological and functional changes in mouse splenic lymphocytes following in vivo and in vitro exposure to chlorphentermine.

With repeated administration to animals, the cationic, amphiphilic drug, chlorphentermine (CP), has been shown by others to induce a phospholipidosis in lymphocytes. In the present study mouse splenic lymphocytes, exposed to CP, either in vivo or in vitro, developed morphological changes consistant with the induction of phospholipidosis. In addition, CP induced functional changes in lymphocytes. Mice, treated with CP in vivo, demonstrated a significantly depressed ability to generate a delayed hypersensitivity response or to produce antibody-secreting cells against de novo antigens. Mouse splenic lymphocytes, exposed to 10(-7) M CP for 3 days in vitro, demonstrated a significantly depressed blastogenic response to the mitogens phytohemagglutinin, concanavalin A and lipopolysaccharide. CP inhibited an event that occurred early during lymphocyte activation, but was subsequent to mitogen/receptor coupling. In addition, CP significantly depressed the increased uptake of choline that occurs in lymphocytes following cellular activation. Since the presence of phospholipidosis is indicative of an impairment in phospholipid metabolism, these results taken together provide evidence for a relationship between this phenomenon and altered immune function.

The mutagenic potential of 25 organophosphinate compounds.

The mutagenic potential of 25 organophosphinate compounds was investigated using the Ames Salmonella/Mammalian Microsome Mutagenicity Assay. Diphenyl, triphenyl, p-nitrophenyl, halogenated and several other derivatives were examined. In all assays performed, there was no evidence of mutagenicity.