Skin ultrastructure in relation to prolactin and MSH function in rainbow trout (Oncorhynchus mykiss) exposed to environmental acidification

Nonylphenol affects the granulation pattern of epidermal mucous cells in rainbow trout, Oncorhynchus mykiss

Nonylphenol is a biodegradation product of nonionic surfactants and has recently attracted considerable attention due to its estrogenic potential. Sexually mature male rainbow trout were repeatedly exposed (one to four periods of 10 days each) to environmentally relevant concentrations of nonylphenol (1 microg/L, 10 microg/L) and for comparison, trout were injected with estradiol. Since estrogens are known to induce structural changes within the fish skin, a similar effect of xenobiotics with estrogen-like activity was assumed. Samples of skin were evaluated by means of light and electron microscopy and histochemistry. In trout exposed to nonylphenol and to estradiol, the structure of the epidermis was altered: an irregular overall architecture was often accompanied by detached pavement cells, vacuolation of the cytoplasm, and severely deformed cell nuclei. However, the granulation pattern of the mucous cells was influenced exclusively after exposition to nonylphenol. The number of large and irregularly shaped mucosomes depended more on the exposure period than on the concentration of nonylphenol. Furthermore, this alteration has not yet been reported for any other pollutant or stressor and, thus, can be classified as an effect that would strongly indicate exposure to nonylphenol.

Modulation of drug-metabolizing systems by bacterial endotoxin in carp liver and immune organs

This report describes a study of the effects of bacterial endotoxin [lipopolysaccharide (LPS)] on cytochrome P450 levels and ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities in liver and two main immune organs of carp: spleen and head kidney. Also studied was the paucity of the carp drug-metabolizing system in an environment subject to pollution by a polycyclic aromatic hydrocarbon, 3-methylcholanthrene (3MC), when fish respond to an immune activation by lipopolysaccharide (LPS). In the presence of bacterial endotoxin the basal cytochrome P450 levels were decreased in liver and spleen. EROD activity was increased in liver and basal GST activity was increased in spleen. When fish were treated concomitantly with 3MC and LPS, a suppression of cytochrome P450 induction in liver and head kidney was observed. EROD activity induced by 3MC was not modified by administration of LPS. GST activity was suppressed by treatment with LPS and inducing agent in liver and head kidney. In the present study it was found that endotoxin can have profound and differential effects on fish basal biotransformation of drugs in the liver and immune organs. Also, the induction of biotransformation enzymes by 3MC was modified when fish responded to an immune stimulation.

Morphometric assessment of epidermal and mucous-biofilm changes caused by exposure of trout to chloramine-T or formalin treatment

Juvenile rainbow trout were exposed to therapeutic concentrations of formalin or chloramine-T to assess the effects of these chemicals on the morphology of the piscine epidermis and its mucous coat. Repeated treatment, once weekly for 4 weeks, with either chemical did not affect the mucous coat of the epithelium or the degree of folding of the basal lamina. However, treated fish had increased numbers of highly dense vesicles within the apical portions of epithelial cells. The epidermal mucous cells of chloramine-T-treated fish were significantly smaller than in controls. This effect was not noted in formalin-treated fish. Treatment with either chemical resulted in a significantly thinned epidermis. It is concluded that although chloramine-T and formalin may continue to be useful in the aquaculture industry they cause potentially harmful alterations to fish skin.

Bacterial lipopolysaccharide (LPS) and interleukin 1 (IL-1) exert multiple physiological effects in the tilapia Oreochromis mossambicus (Teleostei)

To gain insight in immuno-endocrine communication in teleosts the physiological effects of interleukin 1 and bacterial lipopolysaccharide in teleosts were investigated. Tilapia (Oreochromis mossambicus) were treated with murine interleukin 1 and E. coli lipopolysaccharide in vivo, and lipopolysaccharide was administered to pituitary lobes and head kidneys in vitro. The integument of the fish appeared to be a sensitive target for the preparations tested, since proliferation of chloride cells and of epidermal mucous cells was observed as well as an increase in epidermal thickness. These effects may relate to an acute phase-like reaction caused by the treatments. Lipopolysaccharide administration furthermore resulted in an increase in plasma free fatty acids levels. Lipopolysaccharide, but not interleukin 1, stimulated the interrenal axis of the fish, as judged by the increase in cortisol production measured in superfusion of head kidneys. In addition to these in vivo effects, lipopolysaccharide also displayed several effects in vitro. Pituitary adrenocorticotropic hormone, as well as alpha-melanocyte stimulating hormone, release was inhibited, and the head kidney responsiveness to adrenocorticotropic hormone was inhibited after pretreatment of the tissue with the E. coli product. This latter effect coincided with the release of an unidentified alpha-melanocyte stimulating hormone immunoreactive fraction by the head kidneys which could be stimulated by lipopolysaccharide. The data strongly support the notion that the immune system is involved in adaptive regulations in teleosts, and that immunoendocrine interactions are phylogenetically old mechanisms.