Short-lived radionuclides in nutritional physiology. A model study with l-[Me-11C]methionine in the pig

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Abstract
1. A‘new’carbon radioisotope, 11C, for use in nutritional studies is presented. It has a 20 min half-life, and decays by positron emission giving annihilation photons of 511 keV energy (Wolf & Redvanly. 1977). Thus repeated studies can be made with short time intervals and the distribution of radioactivity in the experimental animal can be detected externally.2. 11C was produced with a tandem Van de Graaff accelerator and L-[Me-11C]methionine was synthesized and used in model experiments in the pig. The tracer wasadministered intravenously through a catheter in the jugular vein of pigs weighing between 40 and 100 kg. In a series of experiments, one pig received a low-melhionine diet supplemented with DL-methionine to give three different levels of methioninc intake.3. The radioactivity distribution between liver and muscle was measured as a function of time by external detectors for 2–3 h after administration. Blood and exhaled CO2 were sampled and measured for radioactivity.4. The results indicate that 11C is a useful radionuclide in nutritional studies in intact large domestic animals.