Effect of dimethadione administered intravenously on pancreatic secretion in dogs.

In order to detect both pancreatic excretion of dimethadione (DMO), a weak organic acid, and the effect of pancreatic DMO on secretin-stimulated pancreatic secretion, DMO was given intravenously to dogs with pancreatic fistulae at a dose of 50, 100 and 200 mg/kg. DMO was promptly excreted into pancreatic juice; the concentration decreased exponentially as it did in plasma at the highest dose of the compound. At equilibrium of DMO between pancreatic juice and plasma, the DMO concentration in the juice depended directly on that in plasma; the juice/plasma concentration ratios for DMO exceeded 1.0, ranging from 1.7 to 2.1. Pancreatic DMO caused a small but significant decrease in the water, bicarbonate and sodium secretion at non-equilibrium, and in the bicarbonate secretion at equilibrium. A decrease in the bicarbonate secretion may result largely from the buffer action of bicarbonate on protons provided by the undissociated form of DMO. The sum of both bicarbonate and chloride concentrations in pancreatic juice decreased with the increased DMO concentration in the juice, implying that DMO may compete with the secretion of bicarbonate and/or chloride across the apical membrane of the duct cell. Pancreatic DMO can act as a non-specific inhibitor of pancreatic water and electrolyte secretions.

Effect of dimethadione derived from repeated oral administration of trimethadione on pancreatic secretion in dogs.

The effect of the weak organic acid of dimethadione (DMO) on secretin-stimulated pancreatic secretion was studied with repeated oral administration of trimethadione (TMO), the precursor of DMO, to dogs at a dose of 10 to 160mg/kg/day for a period of 14 days. The bicarbonate concentration in pancreatic juice at a steady state decreased significantly, reflecting a close correlation with the dose of TMO and DMO concentrations in plasma and pancreatic juice. The maximal decrement from the control of cases of no TMO administration was 18.8 mEq/l (12.1% of the control level). The chloride concentration in pancreatic juice showed a reciprocal relation to the bicarbonate concentration. The sum of both anion concentration was constant, irrespective of the dose of TMO. The average carbon dioxide tension of pancreatic juice in all doses of TMO was lower than that of the control, but differences were not statistically significant. The pH, flow rate, sodium and potassium concentrations in pancreatic juice at a steady state did not differ significantly in relation to the dose of TMO. These findings suggest that repeated oral administration of TMO cause a significant decrease in bicarbonate concentration in pancreatic juice, resulting probably from the buffer action of bicarbonate on protons provided from the undissociated form of DMO.

Pancreatic excretion of dimethadione and trimethadione by repeated oral administration of trimethadione in dogs.

To examine pancreatic excretion of dimethadione (DMO), a weak organic acid, as well as of its precursor trimethadione (TMO), TMO was given orally to dogs with pancreatic fistulae at a dose of 10-160 mg/kg/day over a period of 14 days. Blood samples were taken once a day during the administration of TMO and for 7 days after discontinuation of the drug. On the 15th day, pancreatic juice was collected under stimulation by secretin (2 Crick-Haper-Raper units/kg/h). DMO concentration in plasma reached a maximal plateau around the 10th day after starting TMO administration, and depended directly on the dose of TMO. Pancreatic excretion of DMO at a steady state closely depended on both the dose of TMO and the DMO concentration in plasma. The pancreatic juice/plasma concentration ratio for DMO exceeded 1.0 at a steady rate and decreased with the increased flow rate. Pancreatic DMO clearance (DMO output/DMO concentration in plasma) increased, depending on the flow rate, the bicarbonate concentration, and pH of pancreatic juice. Pancreatic excretion of TMO was zero or extremely low.

Macroautoradiographic and densitometric studies of [14C]dimethadione in rats: accumulation of the compound in the pancreas.

Whole-body autoradiographic and densitometric distribution studies were performed on rats to investigate the accumulation of [14C]dimethadione (DMO) in the pancreas. [14C]DMO was intravenously administered at a dose of 167 microCi/0.5 mg/kg. Animals were sacrificed 1, 15, 30, 60 and 180 min after administration of the radioactive compound. The compound was found to rapidly distribute in all body tissues. The distribution pattern of the compound in the pancreas was spotty or linear due to the presence of the radioactive compound in blood of intrapancreatic vessels and in pancreatic ducts at higher levels than parenchyma. The radioactivity of pancreatic ducts became more evident with time, indicating the gradual accumulation of the compound in the ducts. These findings provide morphological evidence that DMO is accumulated in the pancreas and possibly eliminated from pancreatic juice. Densitometry revealed that the levels of radioactive compound in the pancreas were virtually as high as those in the liver and kidney.

Enzymic racemization of allantoin.

Allantoin racemase was isolated from cells of Candida utilis, and purified by chromatography on columns of DEAE-cellulose and Sephadex G-100. Using this purified enzyme, the racemization of allantoin in deuterium oxide was investigated. Polarimetric and PMR spectroscopic analyses showed that racemization of allantoin by the enzyme proceeded in parrallel with release of the hydrogen atom (5-H) attached to the asymmetric carbon (C-5) of allantoin. Non-enzymic racemization of allantoin, which was examined for comparison, however, was accompanied by much less or almost no release of allantoin 5-H. This indicates that the mechanism of racemization by the enzyme differs from that of non-enzymic racemization.

Platelet glycocalicin. II. Purification and characterization.

Glycocalicin, a major glycoprotein of the platelet glycocalyx, is obtained in soluble forms following platelet homogenization and has been purified to homogeneity. Glycalicin has a molecular weight of 148,000 (+/- 5,000) as determined by gel electrophoresis. It contains 60 grams % carbohydrate (46.6 mol %) comprising galactose, N-acetylgalactosamine, N-acetylglucosamine, and sialic acid as its principal sugars in a ratio of 2:1:1:2, but with a small amount of glucose (2.3 mol %), mannose (1.2 mol %), and fucose (1.9 mol %). The principal amino acids are serine and threonine (4.9 and 7.6 mol %), leucine (6.7 mol %), proline, (6.8 mol %), and aspartic and glutamic acids (4.7 and 5.8 mol %). Tryptic digestion of glycocalicin yielded a macroglycopeptide (Mr = 118,000 +/- 5,000) identical with that previously obtained from intact platelets (Pepper, D.S., and Jamieson, G.A. (1970) Biochemistry 9, 3706-3713) and a peptide of molecular weights 45,000 (+/- 2,000) which contained only 7 mol % carbohydrate. This peptide showed a significant enrichment of serine, glycine, and glutamic acids compared with glycocalicin and together these amino acids comprised over 50 mol % of the peptide. Purified glycocalicin gave a single precipitin line with antiserum prepared in chickens. It showed reactions of partial identity with both the macroglycopeptide and the (non-glyco)peptide obtained by tryptic digestion and these showed lines of partial identity with each other. These results suggest that at least three determinants are present in the intact molecule. Glycocalicin gave precipitin reactions with wheat germ agglutinin and with the lectin of Agaricus bisporus.

Stereospecificity of conversion of uric acid into allantoic acid by enzymes of Canadida utilis.

1. Allantoinase [EC 3.5.2.5] was isolated from cells of Candida utilis and unpurified by chromatography on columns of DEAE-cellulose and Sephadex G-200 after treatment with urea to remove urate oxidase [EC 1.7.3.3.]. 2. The purified allantoinase catalyzed the hydrolysis of allantoin into allantoic acid. However, only half of the allantoin produced from uric acid by urate oxidase was converted. The rest of the allantoin was unchanged, and showed a negative optical rotation. 3. On the other hand, the combined action of crude urate oxidase and allantoinase resulted in nearly complete conversion of uric acid into allantoic acid. Furthermore, the unpurified allantoinase preparation hydrolyzed racemic allantoin to allantoic acid completely. 4. These results indicate that the urate oxidase produces racemic allantoin from uric acid and that the allantoinase attacks only allantoin of positive optical rotation. The results also suggest that allantoin racemase is present in the yeast cells.