Induction and localization of hepatic CYP4501A in flounder and rainbow trout exposed to benzo[a]pyrene

The hepatic detoxification system in Baltic flounder and rainbow trout was characterized under experimental conditions. Fish were exposed to benzo[a]pyrene (BaP, 10 and 50mg/kg, ip) or vehicle for 2, 5, and 10 days (in rainbow trout also for 20 days) and then sacrificed. Control fish were sampled at days 0 and 10 (flounder) or day 20 (rainbow trout). The hepatic distribution of CYP1A was analyzed immunohistochemically and microsomal ethoxyresorufin O-deethylase activity was determined spectrophotometrically. The kinetics of the CYP1A responses (EROD) was similar in both species, while a species-specific difference in the magnitude of the response was observed. CYP1A was demonstrated in the hepatocytes in both fish species 2 days after BaP administration and throughout the experiment. In rainbow trout a CYP1A response in the vascular endothelium of liver parenchyma was detected 2 days postadministration, while the corresponding reaction in flounder was seen 5 days postadministration. Thus, our results confirm previous reports that the CYP1A response is species specific. Furthermore, the induction of hepatic CYP1A in Baltic flounder reflects pathophysiological effects induced by polycyclic aromatic hydrocarbon compounds and, consequently, is a parameter useful when monitoring the anthropogenic effects on the Baltic Sea environment.     

Phytosterols act as endocrine and metabolic disruptors in the European polecat (Mustela putorius).

Phytosterols or plant sterols (PS) are consumed as natural remedies and margarines by the general population in developed countries to lower elevated serum cholesterol levels. They are also present in high concentrations in pulp mill effluents. The aim of the study was to screen the endocrine and metabolic parameters of the European polecat (Mustela putorius) for the effects of PS. The results showed an increase in the plasma estradiol and TH levels with no effects on the hypophyseal regulatory hormones. The plasma ghrelin levels decreased. PS also affected intermediary metabolism. The liver glycogen content increased as did the kidney glucose-6-phosphatase activity. The liver lipase esterase activity, on the other hand, decreased due to PS. In serum lipids the total cholesterol did not change, but the low-density lipoprotein levels increased and the high-density lipoprotein-cholesterol ratio decreased. PS had widespread previously unreported effects on the physiology of the polecat. The multiple effects indicate the need of a thorough risk assessment of the effects and interactions of PS.     

Role of gut in xenobiotic metabolism

The gastrointestinal tract forms the first line of defense in the body against the main load of xenobiotics. The gastrointestinal mucosa has several mechanisms through which the xenobiotics are modified. The monooxygenase activities in most species are relatively low in the mucosa as compared to the liver, but conjugation, for example, via glucuronide formation proceeds efficiently. UDP-glucuronosyltransferase activities can exceed those in the liver. Glutathione S-transferase activity is also high. The biotransformation activities are readily inducible in the mucosa and this is, at least partly, responsible for the oral-aboral gradient seen in enzyme activities. In rainbow trout glutathione S-transferase is, however, significantly higher at the aboral third than in two oral segments, although in rats the intestinal glutathione S-transferase shows a clear oral-aboral gradient. The gradient is independent of the presence of microflora at least in the case of carboxylesterase and glutathione S-transferase. A similar gradient can also be found from the gut lumen, in both germ-free and specific pathogen-free rats. The cells in the middle of the villi appear to be most responsive under the influence of inducers. The readily occurring induction in the mucosa provides a suitable model for studies on biological effects to defined compounds and mixtures.Dedicated to Professor Dr. med. Herbert Remmer on the occasion of this 65th birthday     

IN VIVO EFFECTS OF BISPHENOL A ON THE POLECAT ( MUSTELA PUTORIUS )

Bisphenol A (BPA), an environmental estrogen derived from the plastic industry, was given orally via incorporation into the food of 30 male and female polecats at 3 different doses (10, 50, or 250 mg/kg body weight/day) for 2 wk with 10 animals acting as controls. Several hormone levels in the plasma were determined as well as the activities of the phase I and II biotransformation enzymes 7-ethoxyresorufin O-deethylase (EROD), cytosolic glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT). BPA did not cause any macroscopic effects on body mass or the health of the animals. UDPGT and GST activities increased significantly in direct correlation with increasing BPA exposure in females and UDPGT increased in a dose-related manner in males. There was no change in the plasma T4 and testosterone concentrations of the males with increasing BPA exposure. Discriminant analysis indicated that the group receiving 10 mg BPA/kg body weight/d was not different from the control group but the groups receiving 50 and 250 mg/kg body weight/d were different from the control group. This suggests physiological changes in the groups receiving 50 or 250 mg BPA/kg body weight/d.     

Biomonitoring of oil spill in a boreal archipelago by xenobiotic biotransformation in perch (Perca fluviatilis)

The effect of the accidental oil spill (250 tons) in a boreal archipelago (Gulf of Bothnia, Vaasa, Finland) on xenobiotic metabolism of local perch (Perca fluviatilis) was monitored for 1.5 years. The monooxygenase (benzo[a]pyrene, 7-ethoxycoumarin O-deethylase, 7-ethoxyresorufin O-deethylase) and conjugation (UDPglucuronosyltransferase, glutathione S-transferase) activities of perch liver were determined from control areas and those areas where oil had spilled. Only a slight induction in monooxygenase activities was seen in perch caught near the oil spill 4 months after the accident. The induction of monooxygenase activities detected with the fuel oil in laboratory experiments was, however, clear. After a single dose, it rose rapidly and quickly disappeared. Conjugation enzyme activities were not affected in the laboratory.     

Bisphenol A affects endocrine physiology and biotransformation enzyme activities of the field vole (Microtus agrestis)

Bisphenol A (BPA), an environmental estrogen, was given subcutaneously for 4 days to 48 field voles at three doses (10, 50, or 250 mg kg(-1) day(-1)). Plasma sex steroids, thyroxine, weight-regulatory hormones, and liver biotransformation enzymes were determined. There was no mortality in the control group but the mortality in the BPA-exposed animals was significant. BPA increased the plasma testosterone concentrations at 250 mg BPA kg(-1) day(-1). The plasma ghrelin levels measured from pooled plasma increased and at the same time the leptin levels measured from pooled plasma decreased at 50 or 250 mg BPA kg(-1) day(-1). The liver 7-ethoxyrufin-o-deethylase activity decreased slightly at all doses, as did the liver cytosolic glutathione S-transferase activity at 250 mg BPA kg(-1) day(-1). The results show that wild mammals such as the field vole could be more susceptible to BPA than laboratory rodents. More studies on wild mammals are needed to determine the risks of endocrine disruptors in natural ecosystems.     

In vivo effects of bisphenol A on the polecat (mustela putorius)

Bisphenol A (BPA), an environmental estrogen derived from the plastic industry, was given orally via incorporation into the food of 30 male and female polecats at 3 different doses (10, 50, or 250 mg/kg body weight/day) for 2 wk with 10 animals acting as controls. Several hormone levels in the plasma were determined as well as the activities of the phase I and II biotransformation enzymes 7-ethoxyresorufin O-deethylase (EROD), cytosolic glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT). BPA did not cause any macroscopic effects on body mass or the health of the animals. UDPGT and GST activities increased significantly in direct correlation with increasing BPA exposure in females and UDPGT increased in a dose-related manner in males. There was no change in the plasma T4 and testosterone concentrations of the males with increasing BPA exposure. Discriminant analysis indicated that the group receiving 10 mg BPA/kg body weight/d was not different from the control group but the groups receiving 50 and 250 mg/kg body weight/d were different from the control group. This suggests physiological changes in the groups receiving 50 or 250 mg BPA/kg body weight/d.     

Effects of phytosterols on the endocrinology and metabolism of the female raccoon dog (Nyctereutes procyonoides)

Phytosterols (PS) are the analogues of animal cholesterol in various plants. beta-Sitosterol is a PS used in margarines and natural remedies to lower elevated serum cholesterol levels. PS enter the ecosystem via pulp mill effluents. The study investigated the endocrine and metabolic effects of PS on the female raccoon dog (Nyctereutes procyonoides), a canid omnivore. Eight female animals were exposed perorally to 8 mg PS/kg/d for 4 wk with 8 animals in the control group. In the PS-treated females, there was a transitory decrease in the plasma estradiol concentrations with an increase in the plasma follicle-stimulating hormone levels. The plasma triiodothyronine concentrations were higher in the PS group. Serum lipid concentrations decreased in PS-treated and control animals. This probably represents a seasonal adaptation. Most of the cholesterol in raccoon dog serum was high-density lipoprotein cholesterol, unlike that in humans but similar to some other carnivores. Liver and kidney ethoxyresorufin O-deethylase activities were lower in the PS treated females. Data indicate that raccoon dogs may not be a sentinel species for PS effects.     

Seasonal variation of the xenobiotic metabolizing enzyme activities in the liver of male and female vendace (Coregonus albula L.)

The activities of xenobiotic metabolizing enzymes measured in the liver of freshwater vendace (Coregonus albula L.) varied with the seasons. The determinations were made at a constant temperature (18°C) and at the environmental (water) temperature, in which the fish were caught.The monooxygenase activities (benzo[a]pyrene, 7-ethoxycoumarin and 7-ethoxyresorufin as substrates) decreased gradually in the autumn before spawning and increased thereafter. The activities in the male vendace were higher than in the female fish. Slight thermal compensation was seen during water cooling in the autumn from temperatures of 10 to 1°C when benzo[a]pyrene or 7-ethoxyresorufin were used as substrates.UDP-glucuronosyltransferase activity, p-nitrophenol as substrate, increased slowly before spawning and just after the event the activity rose to much higher levels. It did not show any thermal compensation during water cooling in the autumn.The amounts of reduced glutathione, the cosubstrate of the enzyme glutathione S-transferase, varied, being highest in the spring and lowest in the autumn.When studying the xenobiotic metabolizing enzyme activities of fish the sexual maturation and reproduction cycle have to be taken into consideration.