The effect of pregnancy on renal clearance of boron in rats given boric acid orally

Boric acid (H3BO3) has been shown to cause developmental abnormalities in t he offspring of pregnant rats. Comparative data on the renal clearance of b aron (B) in rats and humans, both pregnant and nonpregnant, exposed to bori c acid (BA) would reduce uncertainty in interspecies extrapolation from rat s to humans. The purpose of this study was to evaluate the effect of pregna ncy on the plasma half-life and renal clearance of baron in Sprague-Dawley rats given a single oral dose of boric acid. Far the half-life study, nonpr egnant and pregnant (gestation day 16) rats were given a single dose of 30 mg/kg of boric acid by gavage, and plasma samples were collected at 2-3 h i ntervals. The plasma half-life of boron was determined to be 2.9 +/- 0.2 an d 3.2 +/- 0.3 h in nonpregnant and pregnant rats, respectively. In the clea rance study, nonpregnant and pregnant (GD 16) rats were given a single gava ge dose of 0.3, 3, or 30 mg/kg of boric acid. Boron clearance was slightly higher in pregnant rats(3.3 +/- 0.6, 3.2 +/- 0.5, and 3.4 +/- 0.5 ml/min/kg , respectively) compared to nonpregnant rats (3.1 +/- 0.8, 3.0 +/- 0.6, and 3.2 +/- 0.5 ml/min/kg, respectively), but the difference was not statistic ally significant and not dose-related. Baron clearance was less than creati nine clearance, suggesting tubular reabsorption in both groups. In conclusi on, pregnancy did not appear to significantly alter the renal clearance or the plasma half-life of boron in Sprague-Dawley rats under the conditions o f this study.