Obesity as a risk factor in drug-induced organ injury: increased liver and kidney damage by acetaminophen in the obese overfed rat.

The overfed rat served as the animal model for examining the influence of obesity on the hepatotoxic and nephrotoxic potential of metabolically activated drugs, and acetaminophen served as the prototype drug. Weanling Sprague-Dawley rats were given a standard pellet diet or semisynthetic, energy-dense diet designed to produce obesity. After 24 weeks, when overfed rats outweighed controls by more than 50%, animals received 710 mg/kg of acetaminophen i.p., based on total body weight. Toxicity evaluation included biochemical signs of organ injury over the first 24 hr and histopathologic changes in tissue morphology at 48 hr. Both enzyme release (alanine aminotransferase into plasma, alkaline phosphatase into urine) and frank cellular necrosis in liver and kidney of obese rats greatly exceeded that in pellet-fed controls. Contributing to the potentiation of injury were higher peak plasma concentrations of acetaminophen in obese animals resulting from total body weight dosing. However, liver and kidney injury and mortality remained elevated when peak plasma concentrations were matched by fat-free mass dosing, indicating that increased toxicity also was related to obesity. Incomplete recovery of acetaminophen and metabolites from obese animals (45 vs. 71% in control rats) caused by a functional renal impairment made it impossible to determine the metabolic fate of acetaminophen in overfed animals from the analysis of urine collections. Drug products measured in urine were summed with amounts remaining in carcass at sacrifice, computed as terminal plasma concentrations times respective distribution volumes. These results showed obese rats to form more glucuronide and less sulfate conjugate than did pellet-fed controls, coinciding with clinical evidence for enhanced glucuronidation in obese humans.(ABSTRACT TRUNCATED AT 250 WORDS)