Alan Burkhalter

Mechanisms of chemically induced skin irritation: I. Studies of time course, dose response, and components of inflammation in the laboratory mouse

The possibility that chemicals induce skin irritation by multiple mechanisms was studied in laboratory mice. The time course and dose response to topical application of phenol, croton oil, benzalkonium chloride, ethyl phenylpropiolate (EPP), and methyl salicylate were compared. The responses to each chemical were measured as changes in ear thickness following application to one ear. Maximal responses were as follows: methyl salicylate 20 min, phenol 1 hr, croton oil and benzalkonium chloride 6 hr, and EPP 8 hr. The response to EPP included an early, smaller response at 1 hr. Time courses of the responses were not altered by changing the vehicle in which the irritants were applied or by altering the dose. The rates of regression of the inflammatory responses also varied. Although visibly normal, thickness of ears treated with either phenol or benzalkonium chloride remained 0.05 to 1 mm thicker than solvent-treated control ears for 6 weeks. Although the incidence of prolonged thickness was dose related, it was not determined by the intensity of the acute response; doses of other irritants which produced equivalent acute increases in ear thickness did not produce similar changes. The components of the acute responses, i.e., vascular permeability, change in blood flow, and cellular infiltration, to 5 mg methyl salicylate, 2 mg EPP, and 0.05 mg croton oil were compared in studies of tissue histology, changes in vascular permeability by trypan blue and 125I-labeled bovine serum albumin, and change in local surface temperature as an index of blood flow. The histology of the reactions at the time of maximum response to the chemicals differed. Multiple periods of increased permeability and increased surface temperature were produced by the irritants. The permeability and blood flow responses produced by the irritants varied in number, time of occurrence relative to time of application and to time of maximum response, and in magnitude of the changes. Differences in time courses of the responses which were not altered by experimentally varying rate of absorption and in components of the inflammatory response to the three irritants suggest that chemicals induce skin irritation by multiple mechanisms.

Microsomal enzyme induction by methadone and its implications on tolerance to methadone lethality

MANY investigators have sought to explain narcotic tolerance as a result of increased metabolic inactivation of the drug. No evidence for disposition tolerance has yet been reported, however1–6. On the contrary, tolerance to most narcotic effects seems to be adaptive or cellular tolerance, that is a decrease in pharmacological effects even when enough drug is in contact with target cells in the brain to produce marked effects in naive animals7. We wish to report, however, that metabolic inactivation of methadone, a widely used synthetic narcotic, does increase, with a resulting tolerance to its toxic properties.

Effect of oral administration of methadone on hepatic microsomal mixed function oxidase activity in mice.

Abstract Daily oral administration of methadone (50 mg/kg) brought about a 2-fold increase in the activity of liver N-demethylase in mice within a few days and maintained this high level of activity for the 30-day duration of the experiment. An increase in hepatic microsomal protein and a decrease in pentobarbital sleeping times were noted in the methadone-treated animals. Subcutaneous administration of methadone (20 mg/kg) for 6 days resulted in a much smaller increase in the activity of N-demethylase.

Some effects of 3-methylcholanthrene on uridine diphosphate glucuronyltransferase in the rat and guinea pig

Abstract Treatment of young rats and guinea pigs with 3-methylcholanthrene significantly increased liver microsomal glucuronyltransferase activity. The earliest detectable increase in rat glucuronyltransferase activity occurred between 6 and 12 hr following administration of the polycyclic hydrocarbon, and after 48 hr, glucuronyltransferase activity in treated animals was twice that in control animals. Liver glucuronyltransferase activity was not effected when rats were pretreated with nikethamide, chlorcyclizine or phenobarbital. Administration of d,l-ethionine or actinomycin D, inhibitors of protein synthesis, prevented the increase in glucuronyltransferase activity following 3-methylcholanthrene administration. Kinetic analysis of glucuronyltransferase activity indicated that the Vmax was significantly increased in treated rats and guinea pigs. The Km of the enzyme from 3-methylcholanthrene treated rats was significantly decreased, whereas, the Km of the enzyme from treated guinea pigs was significantly increased. These changes in Vmax and Km suggest that induction of glucuronyltransferase by 3- methylcholanthrene may involve qualitative as well as quantitative changes in the enzyme.

CONVULSIVE RESPONSES IN DEVELOPING CHICKENS.

Summary Spinal cord convulsions elicited by direct spinal cord stimulation and maximal electroshock seizures produced by brain stimulation were studied in 14- to 21-day-old chick embryos and in 31-day-old chicks. In spinal cord convulsions, with high frequency stimulation the duration of leg flexion decreased with age. The curves obtained for the duration of leg flexion as a function of frequency were U-shaped in 14- and 16-day-old embryos. The duration of flexion did not change with higher stimulus frequencies in 19- and 21-day-old embryos, and 31-day-old chicks. In maximal electroshock seizures the duration of flexion decreased with age at each stimulus intensity. The decrease in the duration of flexion with age indicates an increase in the severity of convulsion. It is concluded that the particular pattern and intensity of seizure is related to CNS development and may be influenced by the degree of myelination of the neuronal pathways involved in seizure responses.

Tolerance to methadone lethality and microsomal enzyme induction in mice tolerant to and dependent on morphine

In an attempt to explain a loss of cross-tolerance between morphine and methadone and an increased tolerance to methadone lethality in morphine-dependent mice administered methadone orally for six days, the possibility that methadone was stimulating its own metabolism was investigated. It was found that methadone did enhance its own metabolism two-fold. This increase in activity correlated with the development of tolerance to the lethal effects of methadone as measured by an elevation of the oral methadone LD50. Furthermore, SKF-525A, a potent microsomal inhibitor, abolished this tolerance. The intracerbroventricular methadone LD50 was not altered by six days administration of oral methadone, suggesting that the tolerance observed was dispositional in nature.

Biliary excretion of nicotinamide riboside: A possible role in the regulation of hepatic pyridine nucleotide dynamics

Abstract Female rats fed approximately 5 mg/day/kg of body wt of nicotinic acid- 14 C excreted 10 per cent of the daily ingested label in bile and 57 per cent in urine. Approximately two-thirds of the label in bile was present as nicotinamide riboside. Chemical analysis of nicotinamide riboside indicates that about 7 μmoles/day/kg of body wt are excreted into bile. Chemical and radiochemical analyses both indicate that biliary nicotinamide riboside excretion may account for a major fraction of the hepatic pyridine nucleotide turnover. Nicotinamide riboside was not detected in urine, while 1-methylnicotinamide was present in urine but not in bile. Of the daily dietary intake, 6.7 per cent was excreted in bile as nicotinamide riboside while 19.6 per cent was excreted in urine as 1-methylnicotinamide. After intra peritoneal administration of 150 mg/kg of nicotinic acid or 500 mg/kg of nicotinamide, the hepatic NAD + content increases 2 to 4-fold, accompanied by a marked increase in the turnover of this newly formed NAD + . The biliary excretion of nicotinamide riboside increases up to ten times the normal rate during this period of increased hepatic NAD + turnover. The nicotinamide riboside excretion appears to be related to the elevation of NAD + and is independent of whether nicotinic acid or nicotinamide is used as the precursor. Comparison of the biliary nicotinamide riboside excretion with published values for the urinary excretion of NAD + metabolites during a similar hepatic NAD + increase indicates that the biliary route may be a major pathway for the elimination of hepatic NAD + metabolites. 1-Methylnicotinamide was not found in bile unless very large intravenous doses were given to animals with ligated renal pedicles. The possible role of the biliary system in pyridine nucleotide dynamics and the possible relation of biliary nicotinamide riboside excretion to the secretion of other organic cations into bile are discussed.

Increased lung serotonin and pulmonary edema in mice injected with antiserum to ehrlich's ascites tumor.

Summary Mice injected with a rabbit antiserum to Ehrlichs ascites tumor developed hemorrhagic edematous lungs with a markedly increased serotonin content. Such lung findings were not seen in mouse anaphylaxis.