Renal lymph and interstitial fluid concentration of co-trimazine: an experimental study in dogs

Renal clearance and renal hilar lymph and interstitial fluid concentrations of co-trimazine were investigated in dogs during constant intravenous infusion. The lymph was obtained by direct cannulation of the lymphatics, and the interstitial fluid from small plastic tissue chambers, implanted 4--6 weeks before the experiments. The clearance values for trimethoprim and sulphadiazine, compared to the glomerular filtration rate, as measured by 125I-iothalamate clearance, showed a net tubular secretion of trimethoprim and tubular re-absorption of sulphadiazine. Renal lymph and interstitial fluid concentrations were found to be lower than the plasma concentrations, corresponding well with earlier findings for several other antimicrobial agents. We found a statistically significant difference between lymph/plasma and interstitial fluid/plasma ratios, indicating different composition and origin of lymph and interstitial fluid.