Respiration rates and adenosine triphosphate synthesis in rat liver mitochondria: state 4-3-4 transition experiments.

and intestinal contents is also apparent from a time-course graph (Fig. 1). The amount of methylmercuric chloride produced by the caecal contents is not directly proportional to the time of incubation, but instead rises rapidly to a peak at 2670h and then falls with further incubation. In the presence of the intestinal contents, the peak (at 48h) is sharper, and virtually no HgCI, is methylated at incubation times longer than 60h. It seems possible that the enzymes involved in the biosynthesis of methylmercury are unstable in vitro. The above results provide evidence that the biosynthesis of methylmercury from HgClz is possible in the intestinal tract, particularly in the caecum, and, although only small amounts may be formed, over long periods the absorption of methylmercury synthesized in the gut may contribute significantly to the body burden of mercury in man.