Application of the isolated perfused rat kidney model to assess gender effects on drug excretion.

PURPOSE: To study the effect of gender on the renal disposition of two organic anions, p-aminohippuric acid (PAH) and furosemide (FSM) in the isolated perfused rat kidney (IPK).

METHODS

IPK experiments (3-4 per treatment group) were conducted using kidneys from male and female Sprague Dawley rats. PAH was administered as a continuous infusion (with loading dose, targeted steady-state concentration 10 ug/mL). FSM was added as a bolus dose (2.65 mg, targeted concentration 33 ug/mL). Urine was collected in 10-min. intervals and perfusate was sampled at the midpoint of each collection period. Control (drug naïve) perfusions were performed for both genders. PAH and FSM were measured by HPLC. Kidney viability (GFR [estimated using inulin clearance], sodium reabsorption, glucose reabsorption) was monitored continuously during each perfusion experiment (2-h duration).

RESULTS

Good kidney function was maintained across all study groups, and lower GFR estimates in female kidneys were due to differences in kidney weight. For PAH, kidney weight corrected renal clearance (0.88 +/- 0.37 mL/min/g vs. 0.59 +/- 0.19 mL/min/g) and excretion ratio (3.8 +/- 1.7 vs. 2.2 +/- 0.72) were significantly higher in male kidneys. For FSM, renal clearance was significantly lower in female (0.10 +/- 0.05 mL/min/g) compared to male kidneys (0.15 +/- 0.07 mL/min/g). Mass balance analysis showed that FSM cumulative urinary excretion was significantly higher and kidney accumulation was significantly lower in experiments with male kidneys.

CONCLUSIONS

The study demonstrates that the IPK is a useful model to assess gender effects on renal drug disposition. The renal excretion of organic anions is reduced in female rats, possibly due to gender differences in expression and/or activity of membrane transporters (both basolateral and luminal) in the kidney.