2.5 Estimation of vancomycin in the kidney
Vancomycin concentrations in the kidney were analyzed by LC-MS/MS similar to our previous report (Avedissian et al., 2019) with minor noted exceptions. Samples were diluted 20x and atenolol was used as the internal standard with transitions (m/z) of 267.2 →145.0 (quantifier) and 267.2 →190.0 (qualifier). Briefly, whole kidneys were thawed on ice and homogenized using a Polytron System PT 10-35 GT (Fisher Scientific, Hampton, NH) in a 1:3 (w:v) ratio of kidney : water. The homogenate was centrifuged, and the resultant supernatant was used in the analyses. Calibration curves were prepared using control rat kidney tissue homogenates from the saline-treated group of rats. Vancomycin- containing kidney homogenates were diluted 20 x with control kidney tissue homogenate. Kidney concentrations are expressed as vancomycin (µg)/ kidney (g) of wet kidney tissue. Assays were linear between 1.0 and 60 mg/L. Precision was 3-6% for all measurements, including intra- and inter assay measurements. Greater than 80.27% accuracy was observed in all standards tested, with an overall mean assay accuracy of 102% and all concentrations above the lower limit of quantification were between 85 and 115%.