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

In the present study we examined the metabolic fate of progesterone (P4) in homogenate and tissue minces of the ovaries and testes of Lytechinus variegatus. P4 was metabolized primarily into 5α-reduced metabolites including, 5α-pregnane-3,20-dione (DHP), 3β-hydroxy-5α-pregnan-20-one (3β,20-one), 5α-pregnane-3β,20α-diol (3β,20α-diol), 5α-pregnane-3β,20β-diol (3β,20β-diol), and 5α-pregnane-3α,20α-diol (3α,20α-diol) by both the ovaries and testes. The capacity to metabolize P4 did not differ between the ovaries and testes. However, the relative quantity of 5α-pregnane-3β,20ξ-diol synthesized from ovary and testis tissue minces was about 3.3-fold higher than from homogenate preparations. Differences in the synthesis of 3β,20-one and 3α,20α-diol in both ovary and testis minces were dependent on reproductive state. This study demonstrates the pathway of P4 conversion in the ovaries and testes of L. variegatus and indicates the rapid conversion of P4 into 5α-reduced metabolites in these tissues. Although P4 metabolism is not sex specific, sex-specific responses to P4 metabolites have been demonstrated previously. We hypothesize that the sex-specific responses of the ovaries and the testes to P4 may be associated with receptor-level regulatory processes.

We have examined hepatic levels of microsomal lauric acid hydroxylase activity and cyanide-insensitive palmitoyl coenzyme A oxidative activity in koala (Phascolarctos cinereus) and tammar wallaby (Macropus eugenii) and compared our results to those determined in rat. Microsomal lauric acid hydroxylation was significantly higher in koala than in tammar wallaby or rat. However, cyanide-insensitive palmitoyl-CoA oxidation was absent in the koala. We have also determined the hepatic nicotinamide cofactors in these species. Hepatic nicotinamide-adenine dinucleotide (NAD) and the ratio of NAD/nicotinamide-adenine dinucleotide phosphate (NADP) were higher in koala than in tammar wallaby and rat liver. Reverse transcription of koala liver mRNA, followed by polymerase chain reaction using primers based on highly conserved areas in the CYP4A family led to the cloning of a partial, near full length, cDNA clone with ∼70% nucleotide and deduced amino acid sequence identity to human CYP4A11. The CYP has been named CYP4A15.

This study aims to investigate the effects of the herbicide 2,4-D and the insecticide azinphosmethyl on hepatic antioxidant enzyme activities and lipid peroxidation in tilapia. Fish were exposed to 27 ppm 2,4-D, 0.03 ppm azinphosmethyl and to a mixture of both for 24, 48, 72 and 96 h. Activities of catalase (EC 1.11.1.6), glutathione-S-transferase (GST, EC 2.5.1.18) and the level of malondialdehyde (MDA) in the liver of Oreochromis niloticus exposed to 2,4-D and azinphosmethyl, both individually and in combination, were not affected by the pesticide exposures. However, glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) and glutathione reductase (GR, EC 1.6.4.2) activities in individual and combined treatments, increased significantly compared to controls. Furthermore, glutathione peroxidase (GPx, EC 1.11.1.9) activity increased in individual treatment, while the same enzyme activity decreased in combination. 2,4-D did not affect the activity of superoxide dismutase (SOD, EC 1.15.1.1), but the activity of this enzyme in azinphosmethyl treatment decreased, while its activity increased in combination. Combined treatment of the pesticides exerted synergistic effects in the activity of SOD, while antagonistic effects were found in the activities of G6PD, GPx, GR. The results indicate that O. niloticus resisted oxidative stress by antioxidant mechanisms and prevented increases in lipid peroxidation.

The objective of this study was to characterize rainbow trout (Oncorhynchus mykiss) gill epithelial cells in primary culture by evaluating their ability to maintain glutathione and glucuronide conjugating enzymes. The activity and inducibility of the phase II enzymes was investigated as a function of culture time. Glutathione S-transferase (GST) and UDP-glucuronyltransferase (UDPGT) enzyme activities were measured in freshly isolated cells and in cells cultured for 7 and 12 days. GST activity, determined with 1-chloro-2,4-dinitrobenzene, decreased gradually to 72% after 7 days and to 38% after 12 days in culture compared with freshly isolated cells. There was no significant difference between UDPGT activities in freshly isolated cells compared with cells cultured up to 12 days although a transient decrease in activity was observed at day 7. In vitro induction of the enzymes was studied using β-naphtoflavone (BNF) and 3-methylcholanthrene (3-MC) as inducers. GST activity increased 2-fold after exposure to BNF and 1.5-fold after 3-MC exposure for 48 h in 7 days old cultures. No induction was observed in 12 days old cultures. UDPGT activity was not induced either at day 7 or 12.

Brown cells that are found in the red glands of Mercenaria mercenaria accumulate, detoxify and excrete cadmium. Brown cell involvement in metal detoxification was due in part to endogenous glutathione (GSH) and protein sulfhydryl. Metallothionein (MT) and GSH have been shown to play an important role in metal detoxification in bivalve molluscs. This study showed that the protein sulfhydryl in brown cells of Mercenaria was in fact MT, that brown cell GSH functioned in acute protection against Cd²⁺ toxicity, that GSH provided the initial defense against Cd²⁺ toxicity prior to MT induction and that MT variants were unequal in response to Cd²⁺. During treatment of Mercenaria with 0.5 and 1.0 ppm Cd²⁺, brown cells were analyzed for MT by capillary electrophoresis and GSH colorimetrically after 0.25, 1, 2, 3, and 4 days. The data indicated that the cadmium-binding protein was MT with an apparent molecular weight of 9 kDa determined by gel filtration or 6 kDa as indicated by capillary electrophoresis. Glutathione appeared to prevail in the brown cell acute response to 0.5 ppm Cd²⁺, whereas MT appeared to prevail in the acute response to 1.0 ppm Cd²⁺. Capillary electrophoresis can be used to monitor and quantify MT and its variants in brown cells without need for prior separation of cytosolic components by chromatography. The change in MT-II was greater relative to the change in MT-I in the brown cell acute response to 0.5 ppm Cd²⁺, whereas the change in MT-I was greater relative to the change in MT-II in the acute response to 1.0 ppm Cd²⁺. The variants of brown cell MT appeared to respond differentially to Cd²⁺ depending upon the Cd²⁺ treatment concentration.

This study compares the actions of the intravenous anaesthetics propofol and ketamine on animal behaviour and neuronal activity in the snail Lymnaea stagnalis, particularly in relation to excitatory effects observed clinically. When injected into the whole animal, neither agent induced total anaesthesia. Rather, behavioural activity was enhanced by propofol (10⁻⁵ M) and ketamine (10⁻⁷ M), indicating excitatory effects. When superfused over the isolated central nervous system (CNS), differential effects were produced in two identified neurons, right pedal dorsal 1 (RPeD1) and visceral dorsal 4 (VD4). Resting membrane properties were largely unaffected. However, spike after hyperpolarisation was significantly reduced in RPeD1, but not VD4, with some evidence of increased excitability. In addition, an intrinsic bursting property (post-stimulus burst) in VD4 was altered by propofol (10⁻⁷ M). The results suggest significant excitatory components in the actions of some intravenous anaesthetics, as well as a potential role in modifying excitation and bursting mechanisms in the CNS.

A comparative study of specific activities and in vitro inhibition of brain and serum acetylcholinesterase (AChE; EC 3.1.1.7) and serum butyrylcholinesterase (BChE; EC 3.1.1.8) by DDVP, an organophosphorus pesticide, was conducted in 11 freshwater teleost species belonging to four families (Cyprinidae: common carp Cyprinus carpio, bream Abramis brama, blue bream A. ballerus, white bream Blicca bjoerkna, roach Rutilus rutilus, bleak Alburnus alburnus, ide Leuciscus idus; Percidae: perch Perca fluviatilis, pikeperch Stizostedion lucioperca; Esocidae: pike Esox lucius and Coregonidae: whitefish Coregonus albula). Specific AChE and BChE activities in brain and serum of fish were determined. Brain AChE activity varied among fish species ≈10-fold, ranging from 192.6 to 1353.2 μmol g⁻¹ h⁻¹, respectively in perch and whitefish. All cyprinids had higher brain AChE activity than those of other fish families. Serum AChE activity was 100-fold lower than in brain. Serum BChE activity was found only in cyprinids with the exception of the common carp. It varied from 163.8 to 970.3 μmol g⁻¹ h⁻¹, respectively in roach and bleak. The bimolecular enzyme inhibition rate constants (k_IIs) and pI₅₀ values for DDVP were calculated. Sensitivity of fish AChEs both in brain and serum is similar to those of typical AChEs in mammals. The range of k_IIs was 3.4–51.7×10³ mol⁻¹ l min⁻¹ (pI₅₀s were 5.3–6.5), respectively in white bream and ide. In contrast, fish serum BChE was more sensitive to inhibition than typical BChE and AChE in mammals. Values of k_II for BChE were 1.0–2.5×10⁷ mol⁻¹ l min⁻¹ (pI₅₀ was 8.8–9.2), respectively in ide and bleak.

Doramecin is an antiparasitic drug that may interfere with gamma-aminobutyric acid (GABA) neurotransmission. Some behavioral manifestations are related with GABAergic neurotransmissions as anxiety and seizures. The objective of the present study was to examine the possible central nervous system (CNS) effects of doramectin (100, 300 and 1000 μg/kg, SC) in rats, using anxiety behavioral models, susceptibility to seizures and central neurotransmitter evaluations. The open-field results showed (i) few alterations in locomotion frequency; (ii) a biphasic effect on rearing frequency that may be the consequence of least habituation in open-field; (iii) the reduction of grooming durations might be attributed to a possible anxiolytic effect of doramectin since GABAergic agonists reduced this parameter in apparatus. Our data in the hole board showed no effects in locomotion and rearing frequencies but increased head dipping frequency of rats administered doramectin similarly to anxiolytic drugs. In plus-maze test, doramectin administration increased the number of entries and time into open arms, indicating also an anxiolytic effect. Doramectin protected animals from convulsant effects of picrotoxin, indicative of an anxiolytic pharmacological profile of a drug with GABAergic properties. The alterations observed in central dopaminergic, noradrenergic and serotoninergic neurotransmissions might be the consequence of reinforcement in central GABAergic neurotransmission induced by doramectin. The present results suggest that doramectin has the pharmacological profile of an anxiolytic/anticonvulsant drug with GABAergic properties.

Hepatic blood flow decreases under cholestasis and there is evidence that NO regulates liver microvascular perfusion. Thus, the aim of the present study was to evaluate NO synthesis in cholestasis. Cholestasis was induced by bile-duct ligation (BDL) in male Wistar rats. Bilirubins and enzyme activities were measured in serum. Lipid peroxidation, GSH, GSSG and glycogen were determined in liver. Histopathological analysis was performed. Serum NO₂⁻+NO₃⁻ concentration was measured by the Gries reaction. iNOS immunoblot analysis was carried out using an iNOS polyclonal antibody. After 7 days of BDL lipid peroxidation increased while GSH/GSSG ratio decreased. Serum NO₂⁻+NO₃⁻ and liver iNOS protein were reduced, accompanied by ischemia as revealed by the histopathological analysis. GSH upregulates NO synthesis by increasing iNOS mRNA levels and iNOS activity, thus the reduction of GSH/GSSG ratio may be responsible for the downregulation of iNOS protein and NO synthesis, which in turn may explain the observed ischemia and the decreased hepatic blood perfusion in cholestasis reported by others.

We compared the effect of zinc (0.01, 0.1, 0.5 and 1 mM) at two temperatures (5 and 20°C) on erythrocytes from summer and winter acclimatised carp. An increase in temperature from 5 to 20°C increased the unsaturation index (UI) and relative proportion (UI/SFA) of unsaturated to saturated fatty acids in total lipids of the red cells. At 5°C, the unsaturation index of phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) decreased (30–40%) in the presence of 1 mM zinc. The change in unsaturation of phospholipids in the presence of zinc at 5°C is probably responsible for the alteration in structural integrity of erythrocyte membrane as observed by hemolysis and the decreased thiol group content in the erythrocytes. In light of this result, zinc may be considered an environmental hazard for these fish at low temperatures.