Metabolite extraction procedure kidney

From an in vitro perspective, solubility in water and in organic solvents determines the choice of solvent, which, in turn, influences the choice of extraction procedure and analytical method. Solubility can also indirecfly impact the timeframe of an assay for compounds that are unstable in solution. From an in vivo perspective, the solubility of a compound influences its absorption, distribution, metabolism, and excretion. Both water solubility and lipid solubility are necessary for the absorption of orally administered antimicrobial drugs from the gastrointestinal tract. This is an important consideration when selecting a pharmaceutical salt during formulation development. Lipid solubility is necessary for passive diffusion of drugs in the distributive phase, whereas water solubility is critical for the excretion of antimicrobial drugs and/or their metabolites by the kidneys. 

Liver and Kidney. Liver and kidney tissues collected after the sacrifice of cow 59 (0-day withdrawal) were utilized for isolation of metabolites. The isolation procedure involved acetonitrile extraction followed by solid-phase (C-18 Bond Elut cartridge) extraction of the extracts. Sample cleanup after solid-phase extraction was similar to that of urine. The procedure is described in flow diagram 2. 

Comparative Metabolism. Extracts of dog and rat urine, liver, and kidneys, obtained by the same procedures as the swine extracts, were analyzed by reverse phase Ci8 HPLC. The data showed that urine and both tissues of dogs and rats contained the same four major metabolites A, B, C, and D as swine urine and tissues. Table V contains comparative quantitative data on ractopamine HCl and its metabolites in liver and kidneys of swine, dogs, and rats. The amounts as a percent of total residues in all fractions of ractopamine HCl and the four metabolites were almost the same in the three species in both liver and kidney tissue. The notable differences were that dog liver contained less ractopamine and more Metabolite C, and rat kidney contained more Metabolites A and B and less Metabolite C than the other species. The nonextractable C residues were low in the two tissues of all species. 

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