Fig. 2
Application of purified GEPII 1.0 to determine K+ levels within biological samples. a Schematic workflow of an automatable K+ determination assay. b Urine [K+] of healthy human donors was determined using GEPII 1.0 in vitro and plotted against [K+] in the same samples determined with ion-selective electrodes (ISE, n = 15, P = 0.9625, paired t-test). c Bland–Altman plot showing human plasma [K+] of healthy donors (white circles, n = 15) and hemodialysis patients (red circles, n = 15) determined using ISE and purified GEPII 1.0, respectively. Bias (black dashed line) and 95% limits of agreement (red dashed lines) are shown (n = 15, P = 0.6504, paired t-test). d Comparison of individual K+ levels of human plasma samples determined using recombinant GEPII 1.0 of healthy controls (ctrl, n = 15 ± SD) and hemodialysis patients (HD-P, n = 15 ± SD, ***P < 0.0001, unpaired t-test). e [K+] of mouse urine (n = 11, ±SD), serum (n = 25, ±SD), and bile (n = 7, ±SD) samples quantified with recombinant GEPII 1.0. f Representative images of periodic acid-Schiff stained kidney slices of a control mouse (upper panel) and a mouse after ischemia-reperfusion injury (IRI). Scale bar represents 50 µm. Black arrow indicates a tubular cast; black stars mark dilated tubules with loss of brush borders. g Serum creatinine and serum urea levels of control mice (white bars) and mice after IRI (blue bars, n = 5 for each, ± SD, ***P < 0.0001, unpaired t-test). h Serum (left columns) and urine (right columns) [K+] of control mice (white bars, n = 8 for both ± SD) and mice after IRI (blue bar and yellow bar, n = 18 for serum, n = 3 for urine ± SD, ***P < 0.001, unpaired t-test)
