Drug enterocyte adducts: possible causal factor for diclofenac enteropathy in rats.

BACKGROUND & AIMS: Enteropathy is a frequent complication of diclofenac and other nonsteroidal anti-inflammatory drugs, yet little is known about the underlying mechanism. One possibility is that reactive metabolites of diclofenac form adducts with enterocyte macromolecules, as previously shown for liver. We addressed this possibility by using immunohistochemistry to detect diclofenac adducts. METHODS: Rats were treated orally with diclofenac (10-100 mg/kg) and killed after 1-24 hours, and their gastrointestinal (GI) tracts were evaluated for ulcer number and area. Adduct distribution and intensity were assessed by immunohistochemistry by using a technique to simultaneously process and stain multiple intestinal rings. RESULTS: Drug treatment led to dose-dependent formation of both adducts and ulcers only in small intestine and only in animals with intact enterohepatic circulation. Adducts formed within enterocytes by 1 hour, translocated to the brush border, preceded ulceration and vascular protein leakage, and were intense at sites of ulceration. Adducts and ulcers exhibited a parallel distribution within intestinal quintiles: 3rd > 5th >> 1st. CONCLUSIONS: Diclofenac treatment resulted in the formation of drug adducts in enterocytes. Because this molecular change occurred before ulceration, was dose dependent, and exhibited concordant distribution with extent of ulceration, the results suggest a causal role for drug adduct formation in diclofenac enteropathy.

Aging enhances susceptibility of diclofenac-treated rats to gastric ulceration, while attenuating enteropathy.

Although clinical reports note aging and gender as risk factors for NSAID therapy associated gastroenteropathy, neither variable has been examined in an animal model. We addressed this unknown by comparing the responses of young (4 months) and old (22 months) rats of both genders to oral treatment with diclofenac (10 or 50 mg/kg). Diclofenac produced gastric ulcers only in old rats, with markedly larger lesions in females. In contrast, the small intestines in old rats of both genders given the 50 mg/kg dosage had >30% fewer ulcers and a fourfold decrease in area of ulceration compared to young rats. The small intestine was the only site of lesions after the 10 mg/kg dosage and showed one gender influence, namely, a transiently faster time course of ulcer development in females. Old and young rats given 50 mg/kg showed similar declines in serum levels of the vascular permeability indices-total protein and albumin-despite reduced intestinal damage in the old animals, which suggests additive vascular leakage across the gastric lesions that were evident only in old animals. Serum biochemistry showed no evidence of hepatotoxicity or dysfunction, consonant with small intestine as the primary target for diclofenac toxicity in rats. We provide the first experimental evidence for an aging influence on the gastrointestinal target site of a nonaspirin NSAID.