D. A. Price Evans

Norphenazone, a new metabolite of phenazone in human urine.

Phenazone (2,3-dimethyl-l-phenyl-5-pyrazolone (I) still has a use in metabolic studies in man. According to Brodie & Axelrod (1950) it is metabolized to a 4-hydroxylated derivative (II) which is excreted as a glucuronide. We have recently found norphenazone (3-methyl-l-phenyl-5-pyrazolone) (III), previously reported to occur in the urine of phenazone-treated rats (Schiippel, 1966), also to be present in the urine of man.

The acetylation of sulfamethazine and sulfamethoxypyridazine by human subjects

Individuals can be phenotyped as either rapid or slow “acetylators” by means of a sulfamethazine test. Sulfamethoxypyridazine is acetylated in the human being much less than sulfamethazine. A greater percentage of the sulfamethoxypyridazine in the urine is in the acetylated form in rapid acetylators than in slow acetylators. This indicates that the acetylation polymorphism does influence the acetylation of sulfamethoxypyridazine. Acetyl sulfamethoxypyridazine, unlike acetyl sulfamethazine, was not detectable in the serum under the conditions of the present experiment. The serum concentration of free (i.e., nonacetylated) sulfamethoxypyridazine 30 hours after drug ingestion was not different in the two phenotypes. Possible reasons for the differences in metabolism between the two sulfonamide drugs and also implications for the predilection to sulfamethoxypyridazine toxicity are discussed. Individuals tend to acetylate sulfamethazine to a quantitatively similar extent when tested on two separate occasions. There seems to be significant variability between individuals within a given acetylator phenotype and it is suggested that this may be due to the operation of further genetic factors.

Urinary D-glucaric acid excretion and acetanilide pharmacokinetics before and during diphenylhydantoin administration

SummaryThe pharmacokinetics of a single-dose acetanilide (AA) test, and the urinary D-glucaric acid output (UDGAO) were studied in healthy drug free volunteer subjects before and at the end of a fourteen-day period of medication with 5 mg diphenylhydantoin sodium (DPH) per kg metabolically active mass, thrice daily. The steady state plasma concentration (SSPC) of DPH was also determined. The SSPC of DPH was found to vary from 3.4 to 19.6 µg per ml. The mean UDGAO values increased significantly during DPH medication from 9.5 µmol per g creatinine to 29.5 (p<0.002). The half-life of plasma AA concentration decreased significantly during DPH medication from a mean of 4.2 h to a mean of 2.8 (p<0.001). However, the plasma clearance of AA did not change significantly during DPH medication. The increase of UDGAO whilst on treatment with DPH correlated positively with the SSPC of DPH. The evidence from this study suggests that measurement of UDGAO, which is a measure of the activity of the glucuronic pathway does not necessarily indicate the state of induction of oxidizing enzymes in the hepatic endoplasmic reticulum.

The influence of abo blood groups, secretor status and fat ingestion on serum alkaline phosphatase

Abstract Two experiments have been performed in an attempt to clarify the relationship between liver and intestine alkaline phosphatase iso-enzymes and ABO blood group and secretor phenotype. In the first experiment 6 subjects, each of phenotype O secretor, O non-secretor, A secretor and A non-secretor, were studied on two occasions. On the first occasion a fasting sample was followed by ingestion of a non-fat meal, and blood was taken 2 and 4 h thereafter. A similar procedure was followed on the second occasion except that a fatty meal was ingested. The serum samples had determinations performed of total alkaline phosphatase activity and percentage inhibition thereof by l -phenylalanine which gives a measure of the intestinal contribution. The sera were also all subjected to starch gel electrophoresis. A second intestinal electrophoretic band was found in all sera from O secretors and in none of the sera from the other 3 phenotypes. Males had significantly higher mean fasting alkaline phosphatase levels than females. There was a significant increase in total alkaline phosphatase activity 4 h after a fatty meal in O secretors, as compared with a non-fat meal. O secretor subjects had significantly higher values for percentage inhibition of alkaline phosphatase activity by l -phenylalanine than did the other 3 phenotypes, indicating a larger intestinal contribution to total serum alkaline phosphatase activity. The percentage l -phenylalanine inhibition did not change after either non-fatty or after fatty food. In order to assess the last point a second experiment was performed on a further 12 O secretor subjects. Blood was drawn fasting and 7 sol1 2 h following a synthetic fat meal. Total serum alkaline phosphatase, percentage l -phenylalanine inhibition and percentage urea inhibition (which gives a measure of liver and bone iso-enzyme contributions to total activity) were determined. A considerable variation was observed between individual O secretors, the effect of fat in elevating total serum alkaline phosphatase being much more marked in some individuals than in others. The results again indicated that the proportional contribution of the intestinal iso-enzyme remained constant. This last observation suggests that the mechanism of release of alkaline phosphatase iso-enzymes from parenchymal cell into serum is influenced in a similar manner in both liver and intestine by the O and secretor genes.

MULTIPLE ODONTOGENIC KERATOCYSTS IN A CASE OF THE NOONAN SYNDROME

Summary We present a case of the Noonan syndrome with a new oral complication: multiple odontogenic keratocysts.

Apparent Michaelis constants for the metabolism of [ureyl-14C]tolbutamide by human liver microsomal preparations

Abstract A method is described for the measurement of the amount of l-butyl-3- p -hydroxymethylphenylsulphonyl [ 14 C]-urea (hydroxy-[ureyl- 14 C]tolbutamide) formed in vitro from [ureyl- 14 C]tolbutamide. Very low rates of metabolism can be assayed accurately. K m and V max have been determined for the metabolism of [ureyl- 14 C]-tolbutamide by microsomal preparations from human liver obtained (a) postmortem; (b) as operation biopsy material; (c) from tissue frozen for 1 week at −20°. Frozen microsomal pellets have also been investigated. No significant differences have been found between the Michaelis constants for the four types of preparation, although the values reported are generally lower than those in the literature for the metabolism of other drugs by human liver preparations. Pentobarbitone inhibits the rate of metabolism in vitro of [ureyl- 14 C]tolbutamide in a manner neither fully competitive nor fully non-competitive.

The pharmacokinetics of acetanilide and of diphenylhydantoin sodium

SummaryAcetanilide and diphenylhydantoin have a similar first stage biotransformation in that both are oxidized in the para position of the benzene ring incorporated in each of the two molecules.The elimination of acetanilide from the plasma was studied in thirty healthy volunteer subjects following a single oral dose of 50 mg per kg metabolically active mass (MAM = weight to the power of 0.7). Plasma clearance values varied from 12.4 to 25.11 per hour.A dose of 5 mg diphenylhydantoin sodium (DPH) per kg MAM was then given thrice daily for 13 days to the same volunteers. The steady state plasma concentrations of DPH varied from 3.4 to 19.6 µg per ml.Statistically significant correlation was demonstrated between plasma acetanilide clearance and DPH clearance (r=+0.4984).This finding suggests either a common enzyme acceptor or a common rate-limiting step in the metabolism of the two drugs.It is possible that the pharmacokinetics of other widely used drugs known to be oxidized, especially phenylbutazone, may also be correlated with the kinetics of acetanilide and of DPH. If this were so, then certain individuals might be at a relatively high risk (due to drug accumulation) of developing adverse effects from drugs metabolized mainly by oxidation, and certain other individuals who metabolize these compounds at a fast rate are likely not to derive therapeutic benefit. A single dose study with simple measurement of acetanilide pharmacokinetics could be used to identify these groups.

Plasma trehalase activity in diabetes mellitus.

Abstract Trehalase is an enzyme which hydrolyses the disaccharide trehalose to glucose. This enzyme is widespread in nature and found in various human tissue and in human plasma. Trehalose synthesis and degradation has been considered as possibly having a role in carbohydrate transport mechanisms. Plasma trehalase activity has been found to be elevated in a population of diabetics as compared with non-diabetic controls.

Segregation analysis of α-L-fucosidase activity

SummaryComplex segregation analysis of plasma α-L-fucosidase in 45 British families provides evidence for an additive major gene causing low activities of fucosidase. There was no significant evidence of polygenic heritability or common family environment.

Primaquine and methemoglobin

Methemoglobin formation occurring as a toxic manifestation of primaquine was studied in volunteers to determine whether or not it is an example of genetic polymorphism. No evidence of polymorphism was found.