Fig. 3. Enzyme activities of intestinal contents: 0.4 mL of either 2.5 mM 4-nitrophenyl β-D-glucopyranoside, 4-nitrophenyl β-D-glucuronide, or 4-nitrophenyl-sulfate in potassium phosphate buffer, pH 7.4, was mixed with 0.4 mL of potassium phosphate buffer, and 0.2 mL of intestinal contents prepared from both antibiotics- and vehicle-treated mice and incubated at 37℃ for 30 minutes. The enzyme activities were calculated following measuring the sample's absorbance at 405 nm. Each bar represents the mean activity of respective enzymes+standard deviation of triplicate determinations. ^aThe value significantly different from corresponding vehicle-treated controls at P<0.05.