Incubation of human fecal homogenates with 4-¹⁴C-cholesterol

Abstract

Fresh fecal homogenates from nine subjects consuming solid diets have been incubated for seven days at 37 C with 4-¹⁴C-cholesterol. One series of incubations was conducted under nitrogen, another under air. The extent of bacterial modification of cholesterol to known fecal metabolites varied considerably among the subjects, as expected, but when present such bacteria were shown to be highly active in the conditions used. Production of¹⁴CO₂ was essentially zero in all incubations. Recovery of added¹⁴C from the incubated homogenates following extraction with chloroformmethanol (2∶1 v/v) and evaporation to dryness was quantitative in all cases. About 4% of the labeled cholesterol added appeared to be present in acidic components following incubation. It is concluded that in the incubation system used vigorous bacterial conversion of 4-¹⁴C-cholesterol to metabolites known to be produced in the human intestine could occur readily, in either aerobic or anaerobic conditions. However, CO₂ or other small, relatively volatile fragments labeled with¹⁴C could not be detected.