Increased urinary excretion of formiminoglutamic acid in nitrous-oxide-treated rats and its reduction by methionine

Inhalation of nitrous oxide oxidises cob(I)alamin and inactivates methionine synthetase of which cobalamin is a co-enzyme. The biochemical changes in the rat following exposure to nitrous oxide resemble in some detail the changes present in patients with untreated pernicious anemia due to deficiency of cobalamin. There is a marked increase in the excretion of formiminoglutamic acid in the urine following exposure to nitrous oxide. A significant decrease is produced, while on N2O, by giving methionine. The explanation for these findings is discussed in the light of recent data on the effects of cobalamin inactivation.

Skin histidase activity and urine formiminoglutamic acid (FIGLU) in patients with histidinemia found by screening newborn infants

Skin histidase activities and urine formiminoglutamic acid (FIGLU) levels were measured in 20 patients with histidinemia, identified by Guthrie's screening method, and their family members as well as control subjects. There was a significant positive correlation between skin histidase activities and the amounts of urine FIGLU. Although the difference of skin histidase activity and the amount of urinary FIGLU was significant between any two of the three groups (i.e. controls, parents and patients; p less than 0.005), these levels ranged widely and a considerable number of the cases overlapped among groups. When a discriminant function was computed to obtain the minimum probability of misclassification between the groups using the above two parameters, a better segregation was observed. However, even though the number of misclassifications decreased, the overlapping cases were still present, especially between the parent and patient groups. It is concluded that either skin histidase activity, urine FIGLU, or both, can be used as genetic markers of the disease to a large but still limited extent.

Enhancement of histidine and one-carbon metabolism in rats fed high levels of retinol

Histidine metabolism was studied in rats fed 10% casein diets supplemented with 1000 IU of retinol/g concurrent with or previous to exposure to high levels of dietary histidine (1% or 2%). When a retinol-supplemented 10% casein + 1% histidine diet was fed ad libitum for 21 days, urinary excretion of formiminoglutamic acid (FIGLU) was decreased by 50-70% over the entire period and plasma histidine was reduced by 30-70% for 16 days compared to rats receiving 10% casein + 1% histidine with normal levels of retinol. Rats pretreated for 10 days with a 10% casein diet supplemented with high levels of retinol oxidized 30% more L-[ring-2-14C]histidine to 14CO2 and excreted 76% less of the administered dose as urinary FIGLU compared to control rats not pretreated with high levels of retinol. Depression in growth due to supplementation of a 10% casein diet with 1% histidine were also partially alleviated in rats that were first pretreated with retinol. Activities of histidase, urocanase, and formiminoglutamic acid formiminotransferase (FIGLU transferase) were unaffected by retinol supplementation. The results suggest that retinol supplementation enhances histidine catabolism by exerting a change on one-carbon metabolism.

Oral contraceptives: effect of folate and vitamin B12 metabolism

Women who use oral contraceptives have impaired folate metabolism as shown by slightly but significantly lower levels of folate in the serum and the erythrocytes and an increased urinary excretion of formiminoglutamic acid. The vitamin B12 level in their serum is also significantly lower than that of control groups. However, there is no evidence of tissue depletion of vitamin B12 associated with the use of oral contraceptives. The causes and clinical significance of the impairment of folate and vitamin B12 metabolism in these women is discussed in this review of the literature. Clinicians are advised to ensure that women who shop taking "the pill" because they wish to conceive have adequate folate stores before becoming pregnant.

A case of formiminoglutamic aciduria. Clinical and biochemical studies

We describe a boy who excreted massive amounts of formiminoglutamic acid and hydantoin-5-propionic acid in his urine. He was mildly mentally retarded and epileptic, whereas his twin-brother was completely normal. Loading with L-histidine enhanced the excretion of both metabolites. Treatment was attempted with high doses of folic acid and methionine, but both were without effect on the excretion levels.

Formiminoglutamic aciduria in a slightly retarded boy with chronic obstructive lung disease

A 2-year-old boy excreted massive amounts of formiminoglutamic acid in urine. The substance was identified as authentic formiminoglutamic acid by two-dimensional thin-layer chromatography, column chromatography and enzymatic determination. After alkaline hydrolysis the substance was converted to glutamic acid. Serum amino acid concentrations were normal. The patient had normal serum and erythrocyte folate levels. The red blood cell picture was normal. The leukocytes showed slight hypersegmentation. From the age of 3 months he exhibited recurrent otitis media and severe pulmonary infections. He had a peculiar narrow-headed look and marked universal hypotonia. The mental development was slightly retarded. Glutamate formiminotransferase deficiency is postulated. The findings lend support to the theory of glutamate formiminotransferase deficiency being a rather benign disorder of metabolism.

A liver urocanase deficiency

Two sisters with a rare inborn error of histidine metabolism resulting from urocanase deficiency are being presented. The more common form of familial histidinemia due to histidase deficiency is excluded. The urocanase deficiency is proven by demonstrating increased excretion of metabolites of the product of the urocanase enzyme action. Further, the strongest evidence for the urocanase defect rests on the demonstration of urocanase deficiency and normal histidase activity in liver.

Metabolic responses of folic acid and related compounds to thyroxine in rats

This study deals with the effects of thyroidectomy and feeding thyroid powder on histidine and folic acid metabolism. Normal rats maintained on a soy protein diet, low in methionine but supplemented with vitamin B-12, oxidize approx. 10% of an injected dose of [2-14C]histidine in 3 h and excrete low levels of formiminoglutamic acid. Addition of methionine increases histidine oxidation to approx. 20%. The feeding of thyroid powder or the injection of high levels of thyroxine decreases histidine oxidation and increases formiminoglutamic acid excretion. Surgical thyroidectomy at weaning increases histidine oxidation to approx. 45% and, thus, resembles the effect of methionine in promoting histidine oxidation and decreasing formiminoglutamic acid excretion. The feeding of methionine to the thyroidectomized animal further increases histidine oxidation to 65%. The distribution of folate forms in the liver was determined by column chromatography following administration of a dose of tritiated folic acid. In the normal animal, tetrahydrofolate accounts for 38% of the total folate present. The feeding of methionine increases this to 48%, which is consistent with the observed increase in histidine metabolism. Thyroidectomy increases the percentage of tetrahydrofolate to 63% and the feeding of methionine further increases it to 68%. The percentage of tetrahydrofolate relative to total folate is in proportion to the observed rate of histidine metabolism. The action of thyroidectomy in increasing histidine oxidation may be accounted for by its effect in increasing the proportion of tetrahydrofolate.

Utilization of administered folacin derivatives by rats fed a diet low in methionine and folacin

Rats fed a basal diet low in folacin and methionine or the basal supplemented with 1.5% methionine were injected with either tetrahydrofolic acid, 5-methyltetrahydrofolic acid, 5-formyltetrahydrofolic acid, or folic acid. The level of formiminoglutamic acid (FIGLU) excretion was used as an indicator of the animal's metabolically available folacin. Rats fed the basal diet had no decline in FIGLU excretion after dosing. The methionine-supplemented group had significant decreases in FIGLU excretion after dosing with the folacin derivatives. When rats eating the basal diet were dosed with methionine or homocysteine, FIGLU excretions were again decreased.

Bone marrow studies in myelomatosis

The percentage of fat-cell areas in bone marrow particles from 22 patients with untreated myelomatosis was estimated. In only 1 patient was the mean fat cell area below 25% of the bone marrow area measured. A negative correlation was found between the area of fat cells and plasma cells, indicating a displacement of the fat cell area by the plasma cells. 28% of the patients had empty bone marrow deposits of iron. However, based on a normal iron saturation of S-transferrin and a normal sideroblast count in the bone marrow, the supply of iron to the erythropoiesis was considered sufficient. All patients but one had normoblastic bone marrows. Using a deoxyuridine suppression test in 10 patients, no biochemical defect could be demonstrated. To judge from the correlation coefficient a minor degree (9-14%) of the variation in Hb values could be predicted from the cellularity in the bone marrow while a major degree (70%) could be predicted from the renal glomerular filtration rate. The results do not support a displacement of blood-forming elements, iron deficiency, vitamin B12 or folic acid deficiency to be of general significance in the pathogenesis of anaemia, but agrees with a causal relationship between anaemia and renal failure.

Increased concentration of transcobalamin I in a patient with metastatic carcinoma of the breast

A patient with metastatic carcinoma of the breast and increased plasma cobalamin binding capacity (about 50 nmol/1) is described. The binding protein was identified as transcobalamin I (TCI) by DEAE cellulose ion-exchange chromatography, Sephadex G200 gel filtration and agar gel electrophoresis. Although the total plasma cobalamin concentration (about 20 nmol/1) was elevated, the patient complained of neurological symptoms in accordance with a functional vitamin B12 deficiency. Hence, an inactivation of the coenzyme is suggested by the demonstration of considerable amounts of 5'-deoxyadenosylcobalamin bound to the plasma TCI. Both urinary excretion of FIGLU and methylmalonic acid were within the reference ranges. Reported cases of increased cobalamin binding in patients with nonhaematological malignancy are reviewed. Further investigations to characterize the function of the cobalamin dependent metabolic pathways are necessary to determine the importance of the increased transcobalamin binding in these patients.

Blood and liver folacin activity, formiminoglutamic acid excretion, growth and hematology in guinea pigs fed a folacin deficient diet with and without sulfonamides

Dietary folacin deficiency in the presence and absence of dietary sulfonamides was studied in the guinea pig for the purpose of relating the growth and hematologic effects of folacin deficiency to tissue and biochemical changes. Six-week old female guinea pigs fed control and folacin deficient diets with and without 0.1% sulfonamides for 6 to 7 weeks. Growth was significantly reduced in both groups fed the folacin deficient diets, and 25% of all deficient animals died. Macrocytic anemia was not present, but reduced leukocyte numbers were observed in folacin deficiency. Plasma and red blood cell folacin activities were reduced by about 50% in deficient guinea pigs in the presence and absence of dietary sulfonamides. Both liver total folacin activity and urinary formiminoglutamic acid excretion were not significantly altered by the degree of folacin deficiency obtained in this study.

Effect of folic acid deficiency on pregnant rats and their offspring

Two groups of 63-day-old female Wistar rats were fed a folic acid deficient diet, based on 20% of vitamin-free casein and containing 1% of succinylsulfathiazole, for 5 weeks (group A) and 9 weeks (group B) before being bred, and the same diet was continued through pregnancy and lactation. Three out of eleven (21.3%) and three out of seven (42.9%) rats in groups A and B, respectively, resorbed completely, while no control rat resorbed. No pups from group B survived to weaning. Both groups (A and B) showed depressed feed consumption (although the effect in group A rats was small) and weight gains and increased formiminoglutamic acid excretion in the urine during gestation, and low serum folic acid by the end of lactation. A study of blood components in group A rats revealed leucopenia, granulocytopenia, and increased reticulocyte count. While no congenital deformities were observed in pups from deficient dams, group A and group B dams in contrast to controls produced smaller sized litters with lower birth weights and poor survival rate. Surviving pups from group A dams had decreased weaning weights with significantly lower brain weights and brain DNA per gram of tissue.

A methionine-reversible folate deficiency in rats following the acute administration of diethylnitrosamine and alpha-naphthylisothiocyanate

Acute doses of the hepatotoxic agents diethylnitrosamine (DEN) and alpha-naphthylisothiocyanate (ANIT) to young adult male rats led to the production of a folate deficiency as determined by an elevated urinary excretion of formiminoglutamic acid (FIGLU) 2 to 4 days following administration of the compounds. High dietary levels of methionine significantly reduced the elevated levels of FIGLU produced by the 2 chemicals. Dietary folate had no significant effect on the excretion of urinary FIGLU. Although the hepatic levels of S-adenosylmethionine (SAM) were significantly increased in rats fed the high dietary levels of methionine, an acute dose of DEN did not depress the hepatic levels of SAM. The results indicate that the methyl-reversible folate deficiency caused by hepatotoxic agents is not the direct consequence of altered hepatic levels of SAM.

Effect of methionine on the metabolism of formate and histidine by rats fed folate/vitamin B-12-methionine-deficient diet

The metabolism of formate and histidine were compared in rats and in perfused livers of rats on diets deficient in vitamin B-12, methionine, and folic acid. Excretion of formate and formiminoglutamic acid, and the oxidation of [2-14C]histidine and [14C]formate to 14CO2 were measured. Liver folate levels decreased to 40% of normal on the vitamin B-12- and methionine-deficient diets but the rate of oxidation of histidine to CO2 in the whole animal decreased to 15% of normal. This indicated a reduction in the metabolic activity of the liver folates in vitamin B-12deficiency. Comparison of formate and histidine catabolism in folic acid deficiency showed that the oxidation of histine was decreased to 5% of normal but formate oxidation was decreased to only 30% of normal. This indicates that 25% of formate oxidation normally proceeds by a non-folate-dependent pathway.

Urinary formiminoglutamate in man. Normal values related to sex and age. Effects of low calorie intake and alcohol consumption

A modification of the enzymic method of Tabor and Wyngarden for formiminoglutamate (FIGLU) estimation in urine is described. Alkaline degradation of FIGLU in blanks enhanced the sensitivity of the method. FIGLU excretion in 94 healthy persons indicated a sex and age dependence. Short term calorie restriction or fasting led to a decrease of FIGLU excretion while acute alcohol intoxication or chronic alcohol administration were accompanied by enhanced FIGLU excretion. It is suggested that decreased FIGLU excretion was due to histidine deficiency.

Mobilization of folate from liver into blood stream following histidine injection in rats

A marked reticulocyte response following intraperitoneal injections of histidine monohydrochloride was observed in rats which were fed on a folate-free diet immediately after weaning for a period of 20 days or more. This finding was taken as an evidence for mobilization of folate stored in the liver into blood stream following histidine injection.

Hydantoin-5-propionic aciduria in folic acid nondependent formiminoglutamic aciduria observed in two siblings

Hydantion-5-propionic acid was detected in massive amounts in the urine of two previously described sisters with folic acid nondependent formiminoglutamic aciduria. HPA was identified rigorously, e.g. by gas chromatography-mass spectrometry, and was measured quantitatively by selected ion monitoring (mass fragmentography) using deuterated HPA as internal standard. Before histidine loading, both girls with the postulated formiminotransferase deficiency excreted an amount of HPA more than 50 times greater than the control subjects. After histidine ingestion, HPA excretion was still doubled or tripled. With the exception of the father, the values for the other members of the family also markedly exceeded the normal range and were of the same order of magnitude as in folate deficiency. Measurement of HPA excretion in urine seems to be a valuable supplement or alternative to the enzymatic FIGu test for the detection of general or functional folate deficiency or impaired folate utilization and it will be indispensable for the detection of (as yet unknown) 4-imidazolone-5-propionic acid hydrolase deficiency.