The In Vivo Effects of Adenine-Induced Chronic Kidney Disease on Some Renal and Hepatic Function and CYP450 Metabolizing Enzymes

Adenine-induced model of chronic kidney disease (CKD) is a widely used model especially in studies testing novel nephroprotective agents. We investigated the effects of adenine-induced CKD in rats on the activities of some xenobiotic metabolizing enzymes in liver and kidneys, and on some in vivo indicators of drug metabolism (viz pentobarbitone sleeping time, and plasma concentration of theophylline 90 min post administration). CKD was induced by orally feeding adenine (0.25 % w/w) for 35 days. Adenine induced all the characteristics of CKD, which was confirmed by biochemical and histological findings. Glutathione concentration and activities of some enzymes involved in its metabolism were reduced in kidneys and livers of rats with CKD. Renal CYP450 1A1 activity was significantly inhibited by adenine, but other measured isoenzymes (1A2, 3A4 and 2E1) were not significantly affected. Adenine significantly prolonged pentobarbitone-sleeping time and increased plasma theophylline concentration 90 min post administration. Adenine also induced a moderate degree of hepatic damages as indicated histologically and by significant elevations in some plasma enzymes. The results suggest that adenine-induced CKD is associated with significant in vivo inhibitory activities on some drug-metabolizing enzymes, with most of the effect on the kidneys rather than the liver.

CNS Depressant and Antiepileptic Activities of the Methanol Extract of the Leaves ofIpomoea AquaticaForsk

The central nervous system (CNS) depressant and antiepileptic activities of the methanol extract of the leaves ofIpomoea aquaticaForsk (IAF) were investigated on various animal models including pentobarbitone sleeping time and hole-board exploratory behavior for sedation tests and strychnine, picrotoxin and pentylenetetrazole-induced convulsions in mice. IAF (200 and 400 mg/kg, p.o.), like chlorpromazine HCl (1 mg/kg, i.m.), produced a dose-dependent prolongation of pentobarbitone sleeping time and suppression of exploratory behavior. IAF (200 and 400 mg/kg) produced dose-dependent and significant increases in onset to clonic and tonic convulsions and at 400 mg/kg, showed complete protection against seizures induced by strychnine and picrotoxin but not with pentylenetetrazole. Acute oral toxicity test, up to 14 days, did not produce any visible signs of toxicity. These results suggest that potentially antiepileptic compounds are present in leaf extract of IAF that deserve the study of their identity and mechanism of action.

Variation in barbiturate sleeping time in mice 3. Strain × environment interactions

Environmental factors such as diet, bedding material and temperature at the time of testing affected a 'model' pharmacological response - pentobarbitone sleeping time - differentially in a range of inbred strains. These results are probably explained by variations in the responses of the strains to constituents of the diets and bedding materials used in the experiments. Differences in the results between experiments suggest that there are also fluctuations in the composition of the diets and bedding materials over time. Strain × environment interactions such as those found here may explain differences in strain rankings between experiments. They would also account for some of the variability in results found between laboratories and within a laboratory over time.

Variation in pentobarbitone sleeping time in mice 1. Strain and sex differences

A set of 23 inbred strains of mice was tested for their sleeping time under sodium pentobarbitone anaesthetic. Highly significant strain differences were found. Estimates of the proportion of the variation accounted for by genetic differences ranged from 28% to 42%. In general, males slept longer than females but the size of the sex differences was not consistent across strains. Sleeping times on different test days also varied, indicating that environmental factors were affecting the results. A specially designed experiment failed to detect any differences in within-strain variation.

Variation in pentobarbitone sleeping time in mice 2. Variables affecting test results

The effect of some environmental factors on the pentobarbitone sleeping time (PST) in inbred strains of mice has been investigated. Age, dose level and fasting before the test significantly altered the PST while the source of the drug and regular handling of the mice had no effect. None of these factors affected strains differentially. Unsystematic effects such as litter differences contributed only a small proportion of the total variation in the experiments. The strain rankings were different from those obtained in some previous experiments. The effects of some of the environmental factors on the PST did not always agree with previous work. The implications of these results for the design of similar experiments and the relevance of baseline values in laboratory animals are discussed.