Pharmacokinetic aspects of inorganic nitrate ingestion in man.

Inorganic nitrate and nitrite concentrations were monitored simultaneously in the plasma, erythrocytes, saliva and urine of five subjects following an oral dose of NaNO3 (470 mumols per kg body weight). There was an average 25-fold increase in plasma nitrate only 10 min. after ingestion. Its concentration rose to a peak level of 1.83 mM in 40 min., a value 49 times the preload level. Erythrocyte nitrate followed a similar pattern, but remained at about two thirds of the plasma values. Salivary nitrate showed a positive correlation with plasma nitrate and averaged 9 times the plasma level during 3 hr following ingestion. This is evidence of a concentration-dependent active secretion by the salivary glands. The mean nitrate clearance was 25.8 +/- 2.85 (S.E.M.) ml/min. corrected for a body area of 1.73 m2 (n = 17). The urinary nitrate/creatinine ratio increased 25 to 70 times after loading. These results indicate a predominantly tubular excretion of nitrate. Nitrite was not detectable in any of the body fluids studied except saliva, where it appeared to increase at the expense of nitrate.

Determination of inorganic nitrate in serum and urine by a kinetic cadmium-reduction method.

Nitrate in serum and urine was assayed by a modification of the cadmium-reduction method; the nitrite produced was determined by diazotization of sulfanilamide and coupling to naphthylethylene diamine. After samples were deproteinized with Somogyi reagent, the nitrate was reduced by Cu-coated Cd in glycine buffer at pH 9.7 (2.5 to 3 g of Cd granules for a 4-mL reaction mixture). The reduction followed pseudo-first-order reaction kinetics, a convenient time interval for assay being 75 to 90 min. Maximum reduction (85%) occurred at about 2 h. Detection limits in urine or serum were 2 to 250 mumol/L. This method does not require the reaction to go to completion, does not require expensive reagents or equipment, and can assay several samples simultaneously. Repeated assays of two serum pools gave CVs of 9.0% and 4.7% for nitrate concentrations of 31.4 and 80.2 mumol/L, respectively (n = 20 each). The mean concentration of nitrate was 1704.0 +/- 1294 (SD) mumol/L (n = 21) in untimed normal urine, 81.8 +/- 50.1 mumol/L in serum of 38 renal dialysis patients, and 51.2 +/- 26.4 mumol/L in serum of 38 controls.

Glycogen storage disease type I: laboratory data and diagnosis.

A study of 20 cases of glycogen storage disease type I has shown differences from the classical picture. Hyperuricemia was observed in fewer than half of the cases. All patients had increased triglycerides in serum, but fewer than two thirds had increased concentrations of total cholesterol. There was a consistent increase of aminotransferases in serum. Many textbooks discuss hyperuricemia, lactic acidemia, and lipidemia in this disease without mentioning aminotransferases, and above-normal values for these enzymes ought to be given consideration, to avoid misdiagnosis. Glycogen storage disease type IB was detected by comparing glucose-6-phosphatase (EC 3.1.3.9) activity in frozen and unfrozen portions of the same liver biopsy. Latent activity, which appeared after freezing, increased the total activity to within the normal range (4.7-9.1 mumol/min per gram of tissue, wet weight) in type IB, but not in type IA.

Assay of serum cholinesterase with succinylcholine and propionylthiocholine as substrates.

Serum cholinesterase (E.C. 3.1.1.8) was assayed with succinylcholine as a substrate. The reaction was coupled with choline oxidase and peroxidase in the presence of 4-aminoantipyrine and phenol to produce a red quinone dye that was measured spectrophotometrically. The method requires 25 microliter of sample in a total volume of 1.0 ml. The mean activity for 35 adults of the usual genotype was 74.4 +/- 28 U/l (range 24-125 U/l). Succinylcholine-sensitive individuals had activities below 18 U/l. The same serum samples also were assayed with propionylthiocholine as a substrate. Activities with the two substrates showed a coefficient of correlation of 0.980 (n = 68). However, the method using propionylthiocholine showed more overlap between the activities of succinylcholine-sensitive and insensitive individuals. Assay with succinylcholine thus may offer a more effective method of screening for sensitive individuals, since some escape detection by conventional genotyping with dibucaine and fluoride.

Sandhoff disease: a prevalent form of infantile GM2 gangliosidosis in Lebanon.

All cases clinically diagnosed as Tay-Sachs disease at the American University Hospital, Beirut, during a period of 22 years (1957--1979) were reviewed. Of a total of 15 cases, seven had serum hexosaminidase tested and proved to have Sandhoff disease. In two other cases, parents were tested and found to be Sandhoff carriers. These results indicate that Sandhoff disease is relatively prevalent in Lebanon and that it may represent the more common form of infantile GM2 gangliosidosis in this country.

Ammonia production during clot retraction and its use in assay of fibrinoligase.

Clotting of recalcified plasma is followed by an increase in its ammonia content that lasts 4 to 6 h. This ammonia production closely parallels the increase in acid-insoluble fibrin, which is evidence that the ammonia results from the action of fibrinoligase. If the clot is removed, ammonia production stops. The initial velocity of ammonia production is directly proportional to the fibrinogen concentration in plasma. Thus the rate-limiting factor in normal shed blood is the fibrinogen concentration. A maximum of 6.4 +/- 1.5 (SD) molecules of ammonia are produced per molecule of fibrinogen. Determination of the total ammonia produced is the fastest direct method of estimating the extent of frbrin cross-linkage in whole plasma. A method is proposed for assaying fibrinoligase, based on the rate of ammonia production in the presence of casein as substrate. Normal values are 7.6 +/- 2.9 (SD) mumol/min per liter of plasma.

Isolation of four components from purified human erythrocyte hypoxanthine-guanine phosphoribosyltransferase by isoelectric focusing.

Erythrocyte HGPRT from a male donor was partially purified by DEAE-cellulose chromatography and by fractionation between 35 and 65% ethanol. Isoelectric focusing of the ethanol fraction resolved HGPRT activity into four components which were numbered I-IV beginning with the one nearest the cathode. A second isoelectric focusing of component II (the most active) resulted in 94% of the activity as a single component. When mixed, however, the four components could be separated again by isoelectric focusing. The appearance of these different molecular forms of the enzyme could be due to post-transcriptional alterations or to formation of enzyme complexes.