Determination of Creatinine and Related Guanidinium Compounds

Late-onset ornithine transcarbamylase deficiency in male patients

We report on 21 male patients who presented after 28 days of age with ornithine transcarbamylase (OTC) deficiency, which we define as late-onset OTC deficiency. These patients appeared normal at birth, but irritability, vomiting, and lethargy, which were often episodic, later developed. The age at presentation ranged from 2 months to 44 years. Biochemical testing revealed hyperammonemia, hyperglutaminemia, hypocitrullinemia, increased urinary orotate excretion, and decreased liver OTC activity measured in vitro, which ranged from 0% to 15% of normal. Male patients who were older at presentation had a somewhat different pattern of presenting symptoms and were more likely to die. These data illustrate the phenotypic variability of OTC deficiency. Unexplained episodes of repetitive or protracted vomiting in association with progressive alterations in behavior or neurologic findings should suggest the diagnosis of a urea cycle defect (or another symptomatic inborn error of metabolism), regardless of the age or medical history of the patient.

Allopurinol-induced orotidinuria. A test for mutations at the ornithine carbamoyltransferase locus in women

Ornithine carbamoyltransferase is an X-linked mitochondrial enzyme expressed in hepatocytes and enterocytes. A deficiency of this enzyme results in central nervous system dysfunction, which may be fatal in newborn boys. Milder forms are seen in older boys and girls and in adults. Establishing the carrier status of women at risk for ornithine carbamoyltransferase deficiency is important for determining reproductive and medical risks for affected women. We report a test to establish the carrier status of women at risk for ornithine carbamoyltransferase deficiency. This test relies on the allopurinol-induced accumulation of orotidine, whose synthesis is stimulated by carbamoyl phosphate, a substrate that accumulates in ornithine carbamoyltransferase deficiency. We used anion-exchange, high-performance liquid chromatography to measure urinary orotidine and orotic acid excretion after the administration of a 300-mg oral dose of allopurinol in 25 [corrected] women who were obligate heterozygotes, 13 who were probable heterozygotes, 15 mothers of affected boys from monoplex families (families with only one affected member), 12 mothers of affected girls from monoplex families, and 21 [corrected] normal, unrelated women who were not carriers. Urinary orotidine excretion was increased 3 SD or more above the mean value for the normal women in 95.8 percent of the obligate heterozygotes, 84.6 percent of the probable heterozygotes, 73.3 percent of the mothers of affected boys in monoplex families, and 33.3 percent of the mothers of affected girls in monoplex families, thus establishing that these women were carriers of a mutant ornithine carbamoyltransferase allele. The presence of allopurinol-induced orotic aciduria was not as sensitive or specific an indicator of carrier status as the presence of orotidinuria. We conclude that measurement of urinary orotidine excretion after the administration of allopurinol is a simple and reliable test for the identification of women who are heterozygous for ornithine carbamoyltransferase deficiency.

Calcium channel blockade in experimental aminoglycoside nephrotoxicity

Calcium channel blocker therapy has proved protective in certain models of ischemic-induced acute renal failure. This effect may be related to the prevention of calcium influx into injured cells or by the vasodilatory effects of verapamil that may result in an improvement in renal blood flow. In the current study, the effect of verapamil treatment on the development of renal insufficiency and renal tissue calcium accumulation following aminoglycoside administration was investigated. The degree of functional damage and cortical tissue calcium accumulation after six or nine days of gentamicin administration (120 mg/kg body weight/day) was not significantly different in rats whose drinking water contained verapamil (10 mg/100 cc) than corresponding values in control animals. The tissue calcium accumulation correlated with the degree of reduction of creatinine clearance and probably reflects the extent of lethal tubular cell injury.

The use of 17-epimethyltestosterone radioimmunoassay in following excretion of methandienone metabolites in urine

A radioimmunoassay determination method was developed for 17-epimethyltestosterone (17 alpha-hydroxy-17-methyl-4-androstein-3-one). Excretion of metabolites during and after methandienone (17 beta-hydroxy-17-methyl-1,4-androstadien-3-one) administration was followed in human urine samples by RIA tests for methandienone and 17-epimethyltestosterone. While alternating peaks were found in both measured excretion curves, their addition results in a normal curve showing a plateau between the 3rd and 6th day of the drug administration. Furthermore, due to the presence of higher amounts of epi-configurated metabolites, the new test has a higher effectiveness in the detection of the metabolites.

Ion-exchange chromatographic separation and fluorometric detection of guanidino compounds in physiologic fluids

A high-performance liquid chromatographic procedure has been developed for the separation and fluorometric detection of guanidino compounds in physiologic fluids. All guanidino compounds were separated on a 17 X 0.46 cm cation-exchange column using a stepwise pH gradient. The chromatographic system was designed to enable the use of the specific reagent 9,10-phenanthrenequinone as a means of monitoring the guanidino compounds of physiologic fluids. This new analytical method is so sensitive that it enables the analysis at the picomole level. Our automatic guanidino-compound analyzer was successfully applied to the quantitative determination of all guanidino compounds in physiologic fluids from normal controls and uremic patients.

Gas chromatographic determination of methylguanidine, guanidine and agmatine as their hexafluoroacetyletonates

Seven derivatives of each of methylguanidine, guanidine and agmatine have been prepared, and the specificity and volatility of their gas chromatographic detection have been studied. The hexafluoroacetylacetonates have been found to be the most specific for the three guanidines, and are highly sensitive to alkali flame ionization and electron-capture detections. These derivatives are also fairly resistant to hydrolysis occurring in the derivatization process.

Effects of citrulline administration on enzymes of liver and brain in rats

Intraperitoneal administration of citrulline (30 mg/kg body weight) for three days to rats brought about an increase in the activity of hepatic ornithine-aminotransferase without any change in glutamine-synthetase activity. In the brain of the same animals, the activity of the glutamine synthetase in cerebellum and brain stem increased significantly. In cerebral hemispheres the activity of ornithine aminotransferase was increased without a change in glutamine-synthetase activity. Under these conditions, there is a rise in the content of glutamine, citrulline, arginine and ornithine in all the three regions of the brain.