Effects of Heavy Water on Mammalian Metabolism

Heavy water has hitherto not been subjected to serious pharmacological study in mammals; indeed it has been uncertain whether such activity exists to any significant extent. From its unusual physical characteristics, however, and its effects upon the behavior of lower forms of life (Urey, 1 , 2 Barnes 3 ) depression of function has been generally predicted in mammals. In particular, Barnes 4 has observed, for example, decrease in the rate of activity of the contractile vacuoles of protozoa and finds in 30% heavy water a reduced contraction rate supporting the prediction of chemists that deuterium will be found to have effects similar to those of low temperature.

The oxygen consumption of luminous bacteria in high concentrations of heavy water has been found decreased by Harvey and Taylor, 5 using the Warburg method. The same is true of yeast in 20% (or higher) D₂O. Other instances of depressed function might be cited; that reported in the highest form of life thus far is apparently the slowing of the frog heart recently described by Barnes. 6

Our starting point in mammals has been a study of the metabolic rate of 2 white mice, each treated with several subcutaneous injections of 99% deuterium oxide. The carbon dioxide and water output, oxygen consumption and respiratory quotient have been closely followed, parallel with the variation in apparent content of the body in heavy water.

The method employed was a Haldane open metabolism chain which included some new features which will soon be published in detail by Barbour and Cochran. 7 An essential feature consists in the recovery of 97.5% of the insensibly lost water by passing it through a 100 cc. pipette, surrounded by well-insulated dry ice.