FIGURE 4.

Estimation of the metformin concentration in the liver parenchyma. (A) Known quantities of metformin were spotted either on top of (Over) or under (Under) thin-sections of rat livers perfused without metformin: (a) 5 μM, (b) 10 μM, (c) 25 μM, and (d) 50 μM. (B) Box plot of the pixel values obtained for each spot of metformin. Box lines are median, first and third quartiles, and whiskers show the 2^nd and 98^th percentiles. The average number of pixels for each ROI was 896. (B, inset) Shows the peak intensity for 5 and 10 μM metformin. (C) Standard curve with linear regression calculated from the average of the values obtained by applying standard on top of and under the thin-section, respectively. (D) The mass spectrum of a liver thin-section with 250 nM metformin, as indicated (arrowhead). Arbitrary intensity (A.I.) is reported as in Figure 3.