Renal toxicity of aspirin to rats pre-treated with ethinyl oestradiol

Sex-related differences in renal toxicodynamics in rodents

INTRODUCTION

An issue yet to be addressed, in the investigation of the xenobiotic toxicity, is a detailed characterization of the sex differences in toxicological responses. The 'sex issue' is particularly significant in nephrotoxicology as the kidney is a relevant target organ for xenobiotics and few studies have approached this subject in the past. There is a strong need to improve our understanding regarding the influence of sex in toxicology, given their increased requirement to establish the limits of exposure to chemicals in the environment and at work.

AREAS COVERED

In this review, the authors provide the reader with the current knowledge of sex differences in kidney toxicity for rats and mice. To make the review easier to consult, these studies have been organized according to the class of xenobiotic.

EXPERT OPINION

From the analysis of the present knowledge emerges a dramatic need for information on sex differences in xenobiotics toxicity. Although animals are reasonably good predictors of adverse renal effects in patients, there is need to identify alternative methods (e.g. in vitro/ex vivo) to better study sex differences in organ toxicity.

Does aspirin cause acute or chronic renal failure in experimental animals and in humans?

There are conflicting reports on the ability of aspirin as a single agent to cause acute or chronic renal failure in experimental animals. Chronic administration of aspirin alone over 18 to 68 weeks in doses of 120 to 500 mg/kg/d has been reported to cause renal papillary necrosis in rats. However, some investigators have been unable to produce renal papillary necrosis in other species or in rats given lower divided doses comparable to therapeutic doses used in humans. In a variety of rat strains, aspirin administered as a single high dose intravenously or by oral gavage produces acute tubular necrosis of proximal tubules, rarely accompanied by renal papillary necrosis in susceptible strains. Several human studies have addressed the chronic nephrotoxicity of aspirin alone or relative risk of end-stage renal disease in association with aspirin use after correction for other analgesics. With the exception of one case control study demonstrating a low, but statistically significant risk of end-stage renal disease in association with aspirin use, all other case control studies and several prospective studies have been unable to identify a significant risk of chronic renal failure in patients using aspirin alone in therapeutic doses. In healthy adults, short-term aspirin administration in therapeutic doses has no effect on creatinine clearance, urine volume, osmolar clearance, or sodium and potassium excretion. However, in predisposed individuals with glomerulonephritis, cirrhosis, and chronic renal insufficiency, and in children with congestive heart failure, short-term aspirin use in therapeutic doses may precipitate reversible acute renal failure. Acute aspirin intoxication (>300 mg/kg) frequently causes acute renal failure and doses of 500 mg/kg may be lethal. Chronic salicylate intoxication has been reported to cause reversible or irreversible acute renal failure in association with a pseudosepsis syndrome.

Strain-related susceptibility to nephrotoxicity induced by aspirin and phenylbutazone in rats

Single doses of aspirin induce scattered foci of necrosis of proximal tubules in some strains of rats, whereas acute or sub-acute administration of phenylbutazone causes renal papillary necrosis. Initially, using Sprague-Dawley rats of CFY and CD strains, it became clear that these rats were not as susceptible to these drugs as the literature suggested. Aspirin-induced necrosis was apparently sex-related, being seen in females but could be induced by hormone treatment in males. Male Wistar and Sprague-Dawley rats had reacted differently to administration of phenylbutazone for two weeks. Two experiments were performed with four rat strains: Wistar, Lister-Hooded, Sprague-Dawley, and Fischer-344. The rats were six weeks old at the start of the experiments. Five males and five females of each strain were gavaged with either a single dose of 1,000 mg/kg of aspirin or 200 mg/kg phenylbutazone once daily for four weeks. The drugs were suspended in methylcellulose, which was given to equal numbers of control male and female rats in each experiment. The rats were maintained under standard conditions. Blood and 18-hour overnight urine samples were collected prior to sacrifice. There were no strain-related differences in the types of renal lesions seen, however there were differences in the degrees of responses to the two drugs. With aspirin the female Fischer-344 rats were the most susceptible showing necrosis of proximal tubules of both kidneys and markedly elevated urinary protein concentration and gamma-GT activity. Other females showed less change. Male rats were affected only slightly and males of the Wistar strain were not.(ABSTRACT TRUNCATED AT 250 WORDS)