Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology最新文献

Oxidative damage was assessed through the estimation of lipid peroxides (LP) in the lungs of an ageing short-lived species of reptile, Calotes versicolor, commonly known as the garden lizard. Attempts were also made to trace its relationship with the age pigment, lipofuscin and the antioxidant ascorbic acid. While LP increased with advancing age the contents of both lipofuscin and ascorbic acid did not show appreciable change during maturation (<1–1 year old) but declined during senescence phase (1 to 2–4 year old). While the pattern of age associated changes in LP and ascorbic acid indicate similarity with the pattern observed in most of the mammals, the reduction of lipofuscin in older lizards is a significant departure from the common trend.

Metallothioneins (MTs) have important roles in the homeostasis of essential metals and in the detoxication of heavy metals. They also represent a potential indicator of aquatic contamination by metals. Routine methods are needed for MTs quantification in ecotoxicological studies. This paper investigates the possibility to use the spectrofluorescent properties of Cu-MTs for MTs quantification. Cu displacement of metals coordinated to MTs and spectrofluorimetric determination of the obtained Cu-MTs was tested with commercial MTs and Cu²⁺-induced MTs in roach liver (Rutilus rutilus). Results of this original and simple spectrofluorimetric quantification of MTs presented a good correlation with data obtained with SH quantification, but not with metal summation evaluation of MTs (analysis of Zn, Cu and Cd coordinated to MTs). The three methods showed an clear induction of MTs in roach liver after 7 days of Cu²⁺ exposure. After 14 days of contamination, a reduction of hepatic MTs content was observable and not correlated to liver recovery. Results show that this low cost spectrofluorimetric method is useful to quantify MTs.

Levels of progesterone (P4), testosterone (T) and estradiol (E2) indicated significant variation among individual echinoids during the annual cycle, reflecting generally the variation in gamete development that can be observed among individuals. Testosterone and E2 levels in both the ovaries and testes were higher during the period of gonadal growth. Levels of all steroids were greatly reduced compared to those levels reported for asteroids. Differences in the levels of P4, T, and estrogens between asteroids and Lytechinus variegatus may be related to differences in gonad morphology and nutrient storage capacity between asteroids and echinoids. It was hypothesized that the low levels of steroids detected in L. variegatus reflect paracrine-like mechanisms in cell signaling as compared to endocrine-like mechanisms proposed to be involved in regulating gonad function in asteroids. Both the ovaries and testes of L. variegatus had the capacity to synthesize T and a variety of 5α-reduced androgens including 5α-androstane-3β,17β-diol and 5α-androstane-3α,17β-diol (5α-adiols) from androstenedione (AD) in 8 h. Estrogen synthesis was not detected. The sex-specific pattern of accumulation of 5α-adiols in the ovaries and testes suggests that the 5α-adiols may affect processes related to reproduction in L. variegatus.

We investigated whether angiotensin II (Ang II) and endothelin-1(ET-1) are involved in submandibular hypertrophy in response to repeated treatment with isoproterenol (ISO) in rats. The immunoreactive Ang II (IRAng II) and immunoreactive ET-1 (IRET-1) contents of ISO-induced hypertrophy were significantly higher than those of control glands. Treatment of isolated gland tissues with ISO (1 μM) or dobutamine (1 μM) caused significant increases in the IRAng II and IRET-1 contents of the glands compared with controls. These increases were suppressed by pretreatment with enalapril (3 μM) or captopril (3 μM). Treatment with Ang II (10 μM) also caused an increase in IRET-1 content. Our findings suggest that Ang II and ET-1 are involved in the submandibular gland hypertrophy that develops in rats repeatedly treated with ISO, and that these biologically active peptides may act as growth factors. They also imply that the tissue renin-angiotensin system and Ang II specific receptors are present in the submandibular glands.

Perfusion with the ON channel blocker 2-amino-4-phosphonobutyrate (APB) of dark adapted frog eyecups not only abolished the ganglion cells’ (GC) ON responses and the ERG b-wave, but markedly potentiated the OFF responses of ON–OFF and phasic OFF-GCs and the d-wave amplitude of simultaneously recorded local ERG. Glycinergic blockade by strychnine prevented this potentiating effect in 31 out of 69 GCs, but did not change it at all in the other cells. At the same time the d-wave potentiation was preserved during the glycinergic blockade in all eyecups. The results indicate that glycinergic transmission is involved in the inhibition exerted from ON upon OFF channel in some but not all frog retinal GCs.

The anthelmintic drug praziquantel (PZQ) has a short half-life in the circulation, necessitating repeated daily administration of PZQ for the therapy of larval stages of cestodes. The effect of incorporation of PZQ into multilamellar liposomes on their biodistribution in Mesocestoides corti (syn. M. vogae) infected mice has been examined using [³H]cholesterol as a liposomal marker. Incorporation of PZQ significantly increased the average size of liposomes with 70.3% of [³H]lip.PZQ particles up to 1.9 μm, whereas higher portion of [³H]liposomes (66.3% of total) were of smaller (up to 1.3 μm). Both liposome preparations were given intraperitoneally to avoid rapid sequestration in the liver. There were significant differences between [³H]liposomes and [³H]lip.PZQ-associated radioactivity in peritoneal adherent cells, liver- and peritoneal larvae, liver, spleen and lymph nodes within 16 days of examination. The highest uptake (about 2-fold more [³H]lip.PZQ than [³H]liposomes from the total dose) was found in peritoneal cells on day 1 post therapy (p.t.) followed by a rapid decline. The kinetic of decline in these cells recovered on day 1 p.t. was studied also in vitro. Disappearance of the marker due to the breakdown of liposomes and efflux of lipids and PZQ from cells was slower for [³H]lip.PZQ in comparison with drug-free liposomes and was not completed after 4 days-incubation. Significantly increased levels of radioactivity, more in [³H]liposomes treated groups, were recorded in the liver- and peritoneal larvae between days 8–16 p.t. indicating re-utilization of cholesterol by the larvae. The data suggest that incorporation of PZQ into liposomes contributes to the enlargement of liposome average size and slows down their degradation in phagocytosing cells. In this respect, these cells could serve as the secondary circulating depots for PZQ releasing it slowly to the circulation.

The presence and function of the P-glycoprotein mediated multixenobiotic resistance (MXR) mechanism was demonstrated in numerous aquatic organisms. The aim of this study was to investigate whether in aquatic organisms exists the inherent, species-specific basal level of MXR activity. Here the results of the direct comparison of the basal (noninduced) level of MXR activity measured in several marine (Mytilus galloprovincialis, Monodonta turbinata, Patella lusitanica) and freshwater (Dreissena polymorpha, Viviparus viviparus, Anodonta cygnea) molluscs species are presented. The primary criterion for the assessment and quantification of the basal level of MXR activity was the ratio (R) between the accumulation or efflux of the fluorescent model MXR substrates (rhodamine B or rhodamine 123) in or from the gills, measured with and in the absence of model MXR inhibitors verapamil or cyclosporin A. Significantly different levels of MXR activity were found in the species investigated. These levels generally show a relatively good correlation with the level of pollution present in their natural habitats. Considering these results a conclusion was reached that in aquatic organisms indeed exist the different inherent, species-specific levels of MXR activity. The identified levels might be, at least partly, responsible either for the resistance to, or for the sensitivity of a particular species to organic pollution.

The present study was undertaken to compare the effects of allyl mercaptan (AM), a major metabolite of garlic, with several garlic constituents and extracts on cytotoxicity, cholesterol synthesis and its secretion in Hep-G2 cells. The cells were grown in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), and treated with 5, 25, 50, 125, 250 and 500 μg/ml of AM, diallyl disulfide (DD), diallyl trisulfide (DT), steam-distilled garlic oil (SD) or vinyl-dithiin oil of garlic (VD) for 4 h. At concentrations up to 50 μg/ml, no significant cytotoxic effect was found in any group, but at concentrations above 250 μg/ml, the cell viability decreased drastically in all groups compared to the control. The treatment of cells with 25 μg/ml (non-cytotoxic concentration) of AM, DD, DT, SD for 4 h significantly inhibited [³H]acetate incorporation into cholesterol compared to that of the control (P<0.05). The secretion of cholesterol into the medium was also significantly decreased in all groups except for VD. The treatment of cells with those allium constituents had no effect on either [³H]acetate incorporation into fatty acids or [³H]glycerol incorporation into triglyceride or phospholipid.

In the present study, we have examined in Wistar rats the effects of food or water deprivation of 3 days on the hypophyso–adrenal axis, vasopressinergic system and activity of A1 noradrenergic brain stem cell group, which is involved in the control of the hypothalamic neuro-endocrine activity. Levels of adrenocorticotropic hormone (ACTH) and vasopressin (AVP) were determined by radio-immunoassay, and corticosterone level was determined by fluorimetric method. Plasma levels of ACTH and corticosterone were greatly increased in both groups of rats. In water-deprived rats, plasma AVP (13.83±1.63 vs. 3.03±0.23 pg/ml) and osmolality levels were significantly elevated with a marked decrease of AVP hypophysis content (272±65 vs. 1098±75 ng/mg protein), but not in food-deprived rats in which osmolality did not change and AVP remained stocked (2082±216 ng/mg protein) in the hypophysis without release in the plasma (1.11±0.23 pg/ml). These observations indicated that both food-deprivation and water-deprivation stimulated the pituitary–adrenal axis thereby suggesting a stress state. AVP production is stimulated both by fluid and food restriction but is secreted with differential effects: during food restriction AVP secretion is limited to supporting the hypothalamic–pituitary–adrenal system.