INORGANIC SALTS IN NUTRITION

Influence of obesity on sulfonamide disposition in Zucker rats

The genetically obese Zucker rat was used as a model of obesity and compared to its lean littermate to assess and quantify obesity-altered changes in the in vivo disposition of six sulfonamides. Body composition determination indicated that the obese rats were twice the weight of lean rats and a distinct trend towards an increase in fat free mass and total body water was observed. The sulfonamide blood concentration was measured by colorimetry after a 7 mg/kg intravenous dose. All sulfonamides exhibited a biexponential decline of blood concentration with time. The volume of distribution and clearance of sulfanilamide in lean and obese rats were similar resulting in similar elimination half-lives. A decrease in clearance coupled with a trend towards an increase in volume of distribution prolonged the elimination half-life of sulfadiazine in obese rats. For sulfapyridine, sulfamerazine, sulfisomidine and sulfisoxazole, increases in the volumes of distribution and clearances resulted in similar elimination half-lives in lean and obese rats. The free fractions of the sulfonamides were significantly increased in the serum of obese rats, the influence of which on the volume of distribution and clearance is discussed.

Weight gain and body composition in lithium treated rats

Long-term lithium treated growing animals given 0.8-2.0 mmol/kg/day had a slightly but significantly faster weight gain than control animals. Greater doses did not give rise to significantly increased weight gain. Body composition, i.e., the percentage of water, fat, ash and "protein" was not affected in the faster growing lithium treated animals. The wet weight and the weight after drying of the stomach (with content) was increased shortly (hours) after the acute administration of lithium. The duration of the effect depended on the dose given. The weight of the large intestine was also increased after a dose of lithium, but only after some days of lithium pretreatment and mainly the wet weight. The effect was small but similar on the small intestine. In long-term lithium treated rats did the faecal weight and volume increase mainly due to increased water content, but only after some days of lithium treatment.

In vivo determination of body composition by tritium dilution in the rat

Total body water was determined in vivo by tritium dilution in thirty-two male and female rats. Body water obtained by tritium dilution and body fat calculated from this value correlated significantly with body water and fat obtained by analysis (r 0.985, 0.855 respectively). There was no significant difference between values for fat assessed by the direct and indirect methods.