SYNOPSIS Urinary excretion of urocanic acid and formimino-glutamic acid in abnormal amounts following oral doses of histidine has been observed not only in most cases of megaloblastic anaemia, but in iron-deficiency anaemia, haemolytic anaemia, and neoplastic disease.The urinary excretion of these substances is increased in those disease states in which an abnormally rapid rate of removal from the plasma of intravenously injected folic acid has been demonstrated.

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SYNOPSIS Methods of preparing liver for the microbiological assay of folic-acid activity have been compared. Maximum values were obtained by incubating an alkaline homogenate of liver in the presence of ascorbic acid for five hours at 37°C. Most other procedures resulted in significant loss of folic-acid activity.Various methods are available for assessing the folic-acid status of man. These include measurement of the urinary excretion of formiminoglutamic acid (Silverman, Gardiner, and Bakeman, 1952), the measurement of the rate of removal of an intravenous dose of folic acid from the plasma (Chanarin, Mollin, and Anderson, 1958) and the microbiological assay of L. casei activity of serum (Baker, Herbert, Frank, Pasher, Hutner, Wasserman, and Sobotka, 1959). The application of these methods to the study of patients with megaloblastic anaemia has added considerably to our understanding of these disorders. However, it still remains unproven whether an abnormal result with one or all of these tests always means that there is a significant reduction in the folic-acid content of the tissues, and if so, whether this depletion is below the levels required for the performance of the normal biochemical processes of the body. This problem can be answered in part by the measurement of the folic-acid content of body tissue. The ideal organ is the liver, since it not only contains by far the largest amount of folic acid in the body but unlike other tissues contains enzymes which appear to convert hepatic folic acid into a form available to microbiological assay organisms.The purpose of this study was to investigate the conditions under which folic-acid-like materials could be released from the liver for microbiological assay. This paper reports some of our results. MATERIALS AND METHODSANIMALS Albino rats weighing 150 to 200 g. maintained on stock diets were killed by neck dislocation and the livers transferred into a petri dish.

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