The effect of age and long-term low-level DDT exposure on the response to enzyme induction in the rat

Comparability of in vitro and in vivo methods for the determination of alterations in drug metabolism

The above series of experiments taken in toto suggest the usefulness of lindane as a model substrate for studying the effects of a variety of compounds on drug metabolism in vivo. Excellent correlations were observed in comparison with the in vitro measurements both qualitatively and quantitatively. Unlike some of the other compounds discussed lindane offers some distinct advantages. One is that because the metabolites can be monitored in the urine, it is non-invasive in nature. A second is that a number of mixed function oxidase pathways (phase I reactions) can be determined at the same time. This would be of great importance if the effect of a compound is rather selective and does not alter the single pathway measured in the metabolism of other substrates which have been suggested as model compounds. However, the tradeoff is obviously the need for more analytical work. A third advantage is the ability of the system to detect changes in conjugative or phase II reactions at the same time. Further studies will be necessary with all of these model substrates to detect their usefulness and their limitations.

Effects of age and obesity on the metabolism of lindane by black a/a, yellow Avy/a, and pseudoagouti Avy/a phenotypes of (YS x VY) F1 hybrid mice

Lindane (gamma-hexachlorocyclohexane) has been shown to produce hepatomas in some strains of mice but not in others. Genetic factors and/or altered metabolism may play a role in the susceptibility to lindane-induced hepatomas. This study reports the effect of age and obesity on the comparative metabolism and disposition of lindane in obese yellow Avy/a and in lean pseudoagouti Avy/a and black a/a phenotypes of (YS x VY) F1 hybrid female mice at 8, 17, 30, 56, and 86 wk of age. At 24 h prior to sacrifice the mice were dosed p.o. with 18 mg lindane (containing 55 microCi [U-14C]lindane/kg). Aging altered the biotransformation of lindane such that while the excretion of lindane and its metabolites declined, the proportion of conjugated and polar metabolites increased. Tissue storage was elevated in older animals. In the yellow Avy/a mice, which are known to have a predisposition to the formation of hepatomas, there was accelerated and prolonged growth, reduced metabolite excretion, a greater proportion of conjugated metabolites, and higher dechlorinase activity compared to that of their pseudoagouti Avy/a and black a/a siblings.

Comparative study of dieldrin effects on amphibian liver and early embryo phospholipids

1. The effect of Dieldrin on phospholipid content and composition was compared in adult frog liver and in early embryos. 2. Male frogs are more resistant to acute Dieldrin treatment than females. Total phospholipids content increases in the liver of male animals while in females decreases. 3. Early embryo development was not affected morphologically by the addition of 0.02-10.0 mg of Dieldrin/1; however phospholipid content and composition was altered. 4. Adaptive changes in the embryo due to chronically administered Dieldrin is suggested.

Evaluation of the toxic risk of DDT in the rat: during accumulation

An investigation was undertaken on the accumulation of DDT and its metabolites in the rat. Rats received 14.5 mg DDT/kg b.w. every day for 52 days. Growth, food intake, body composition, and the activities of various enzymes were little affected. However, the level of total lipids fell 30% and the weight of the liver rose 20% due to cellular hypertrophy induced by the DDT. The quantity of DDT and its metabolites found in the carcass was 24 mg/rat i.e. three times that found in rats dead after a single dose of 200 mg/kg. Liver and brain contained 130 micrograms/rat and 10 micrograms/rat, respectively i.e. five times lower than those found in the rats which died from an acute dose of DDT. In the carcass, p,p' DDT accumulates more than p,p' DDE or p,p' DDD; the latter is preponderant in the liver.