Creatine and Creatinine *

The first review of the literature on creatine and creatinine after the advent of the Folin colorimetric method was presented by Professor Mendel22 before a joint meeting of the Section on Physiology and Experimental Medicine of the American Association for the Advancement of Science and the biochemical, physiological and bacteriological societies in Baltimore in 1908. Although only four years had elapsed since Folin introduced his new method, it had already stimulated a sufficiently large number of investigations to warrant a symposium and general review of the subject. In his review Mendel presented a critique of investigations already reported, and made pertinent suggestions as to fruitful lines of future research. It will be. of interest to consider some of these remarks in the light of the twenty-three years of subsequent investigation. In discussing the enzymatic transformations of creatine and creatinine proposed by Gottlieb and his co-workers, Mendel comments, "truly a bewildering array of enzymatic processes". Referring to the creatine-feeding experiments of Folin and of Klercker he questioned their conclusion that there is no conversion of administered creatine to creatinine. Turning from critique to suggestions regarding new investigations the following pertinent comments may be quoted: "How constant is the creatine content of adult muscle; and is it altered during activity? In the light of the meager and conflicting data available today, a satisfactory answer cannot be given to these questions. Yet they are of fundamental importance for any adequate discussion of the role of creatine. Mellanby's convincing experiments on isolated muscle showed that muscular work leaves creatine unaffected, as does the survival of muscle." . . . "In this connection it is of interest that according to Urano, the creatine of the muscle appears to be held in some non-diffusible form in the contractile tissue and is only released when the integrity of the muscle bundles is impaired." And again, "At the outset we need to know more definitely about the possible distribution of creatine in the tissues and