Peroxidation of mullet and rat liver lipids in vitro: effects of pyridine nucleotides, iron, incubation buffer, and xenobiotics.

1. Lipid peroxidation was observed in homogenates of mullet and rat livers and was affected by the specific conditions used for the in vitro assays. 2. Lipid peroxidation was altered by the buffer used in the assays and was dependent on the amount of Fe added to the assay. 3. Lipid peroxidation was stimulated by both NADH and NADPH and by the xenobiotics, CCL4 and DEM. 4. Lipid peroxidation was observed in microsomes of mullet livers and was inhibited by addition of cytosol.

Effects of metals and organic compounds on hepatic glutathione, cysteine, and acid-soluble thiol levels in mullet (Mugil cephalus L.).

The hepatic acid-soluble thiol content of striped mullet (Mugil cephalus) exposed to cadmium (10 mg/liter seawater), mercury (200 micrograms/liter), fluorene (100 micrograms/liter), dibenzofuran (750 micrograms/liter), or a 20% water-soluble fraction of a No. 2 fuel oil, and of winter flounder (Pseudopleuronectes americanus) exposed to pentachlorophenol (200 micrograms/liter) for up to 3 weeks was determined. Exposure to these chemicals caused an elevation of hepatic acid-soluble thiol content over control values. Similarly, the acid-soluble thiol content was 1.75 times control values 24 hr after injection with acetaminophen (40 mg/100 g body wt, ip). In contrast, hepatic acid-soluble thiol concentrations did not fluctuate after feeding or during short-term starvation, or after acute or chronic physical trauma. Thus, the increase in hepatic acid-soluble thiols observed in mullet appears to be a specific response to chemical insult. The effect of chemical exposure on specific thiols can vary with the compound under investigation. Glutathione accounted for most of the acid-soluble thiol increase observed in mullet exposed to oil, whereas other acid-soluble thiols were also elevated after exposure to cadmium. Injection of [14C]glycine into cadmium- and oil-treated mullet showed that hepatic uptake of this amino acid substrate and its incorporation into hepatic glutathione increased after chemical exposure. The proportion of the total [14C]glycine in the liver incorporated into glutathione was unchanged after oil exposure, but was significantly increased in cadmium-exposed fish. These results suggest that chemicals may elevate glutathione content by enhancing the hepatic uptake of amino acid substrates and also the activity of biosynthetic enzymes.

High-performance liquid chromatography of corticosteroids in vertebrate plasma: assay of cortisol in mullet and corticosterone in the rat.

Plasma corticosteroids of eighteen vertebrate species were separated by reversed-phase high-performance liquid chromatography (HPLC). The major corticosteroids identified in these species by HPLC agreed with previous reports which used vigorous criteria for identification. The HPLC technique was validated for the assay of cortisol in mullet plasma and corticosterone in the rat. Qualitative as well as quantitative changes in corticosteroid secretion were detected by HPLC in several vertebrates during exposure to stress.