Changes in iron metabolism during prolonged repeated walking exercise in middle-aged men and women.

PURPOSE: The aim of the present study was to assess the effect of prolonged and repeated exercise on iron metabolism in middle-aged adults and to compare differences between sexes. METHODS: 50 male (58.9 ± 9.9 year) and 48 female (50.9 ± 11.2 year) individuals were monitored on 4 consecutive days at which they walked on average 8 h and 44 min per day at a self-determined pace. Blood samples were collected 1 or 2 days prior to the start of the exercise (baseline) and every day immediately post-exercise. Samples were analysed for iron, ferritin, haemoglobin, and haptoglobin concentrations. RESULTS: Plasma iron decreased across days, while ferritin increased across days (both p < 0.001). Haptoglobin showed a decrease (p < 0.001) after the first day and increased over subsequent days (p < 0.001). Haemoglobin did not change after the first day, but increased during subsequent days (p < 0.05). At baseline, 8% of the participants had iron concentrations below minimum reference value (10 µmol/L), this increased to 43% at day 4. There was an interaction between sex and exercise days on iron (p = 0.028), ferritin (p < 0.001) and haemoglobin levels (p = 0.004), but not on haptoglobin levels. CONCLUSION: This study showed decreases in iron, increases in ferritin, a decrease followed by increases in haptoglobin and no change followed by increases in haemoglobin. This is most likely explained by (foot strike) haemolysis, inflammation, and sweat and urine losses. These processes resulted in iron levels below minimum reference value in a large number of our participants.

Increased hypothalamic serotonin turnover in inflammation-induced anorexia.

BACKGROUND: Anorexia can occur as a serious complication of disease. Increasing evidence suggests that inflammation plays a major role, along with a hypothalamic dysregulation characterized by locally elevated serotonin levels. The present study was undertaken to further explore the connections between peripheral inflammation, anorexia and hypothalamic serotonin metabolism and signaling pathways. First, we investigated the response of two hypothalamic neuronal cell lines to TNFα, IL-6 and LPS. Next, we studied transcriptomic changes and serotonergic activity in the hypothalamus of mice after intraperitoneal injection with TNFα, IL-6 or a combination of TNFα and IL-6. RESULTS: In vitro, we showed that hypothalamic neurons responded to inflammatory mediators by releasing cytokines. This inflammatory response was associated with an increased serotonin release. Mice injected with TNFα and IL-6 showed decreased food intake, associated with altered expression of inflammation-related genes in the hypothalamus. In addition, hypothalamic serotonin turnover showed to be elevated in treated mice. CONCLUSIONS: Overall, our results underline that peripheral inflammation reaches the hypothalamus where it affects hypothalamic serotoninergic metabolism. These hypothalamic changes in serotonin pathways are associated with decreased food intake, providing evidence for a role of serotonin in inflammation-induced anorexia.

Vitamin D deficiency as adverse drug reaction? A cross-sectional study in Dutch geriatric outpatients.

PURPOSE: Adverse drug reactions as well as vitamin D deficiency are issues of public health concern in older people. However, relatively little is known about the impact of drug use on vitamin D status. Our primary aim is to explore associations between drug use and vitamin D status in older people. Furthermore, prevalences of drug use and vitamin D deficiency are estimated. METHODS: In a population of 873 community-dwelling Dutch geriatric outpatients, we explored the cross-sectional relationships of polypharmacy (≥5 medications concomitantly used), severe polypharmacy (≥10 medications), and use of twenty-one specific drug groups, with serum 25-hydroxyvitamin D (25(OH)D) by analysis of covariance. RESULTS: Overall prevalence of polypharmacy was 65 %, of severe polypharmacy 22 %. Depending on the cut-off value, prevalence of vitamin D deficiency was 49 % (<50 nmol/l) or 77 % (<75 nmol/l). Of the patients using a vitamin D supplement, 17 % (<50 nmol/l) or 49 % (<75 nmol/l) were still deficient. In non-users of supplemental vitamin D, after adjustment for age and gender, negative associations were found for severe polypharmacy, metformin, sulphonamides and urea derivatives (SUDs), vitamin K antagonists, cardiac glycosides, loop diuretics, potassium-sparing diuretics, ACE inhibitors, and serotonin reuptake inhibitors; for non-selective monoamine reuptake inhibitors (NSMRIs) the association was positive. The most extreme impacts of drug use on adjusted mean 25(OH)D were -19 nmol/l for SUDs and +18 nmol/l for NSMRIs. CONCLUSION: Drug use should be considered a risk factor for vitamin D deficiency amongst geriatric outpatients.

Absorption, distribution, and biliary excretion of cafestol, a potent cholesterol-elevating compound in unfiltered coffees, in mice.

Cafestol is a diterpene present in unfiltered coffees. It is the most potent cholesterol-elevating compound present in the human diet. However, the precise mechanisms underlying this effect are still unclear. In contrast, cafestol is also known as a hepatoprotective compound, which is likely to be related to the induction of glutathione biosynthesis and conjugation. In the present study, we investigated whole-body distribution, biliary excretion, and portal bioavailability of cafestol in mice. First, dissection was used to study distribution. Five hours after an oral dose with (3)H-labeled cafestol, most activity was found in small intestine, liver, and bile. These results were confirmed by quantitative whole-body autoradiography in a time course study, which also showed elimination of all radioactivity within 48 h after administration. Next, radiolabeled cafestol was dosed intravenously to bile duct-cannulated mice. Five hours after the dose 20% of the radioactivity was found in bile. Bile contained several metabolites but no parent compound. After intestinal administration of radioactive cafestol to portal vein-cannulated mice, cafestol was shown to be rapidly absorbed into the portal vein as the parent compound, a glucuronide, and an unidentified metabolite. From the presence of a glucuronide in bile that can be deconjugated by a bacterial enzyme and the prolonged absorption of parent compound from the gastrointestinal tract, we hypothesized that cafestol undergoes enterohepatic cycling. Together with our earlier observation that epoxidation of the furan ring occurs in liver, these findings merit further research on the process of accumulation of this coffee ingredient in liver and intestinal tract.

Drug use is associated with lower plasma magnesium levels in geriatric outpatients; possible clinical relevance.

BACKGROUND: Hypomagnesemia has been associated with diabetes, cardiovascular disease, and other disorders. Drug use has been suggested as one of the risk factors for low magnesium (Mg) levels. In the elderly population, prone to polypharmacy and inadequate Mg intake, hypomagnesemia might be relevant. Therefore, we aimed to investigate associations between drug use and plasma Mg. METHODS: Cross-sectional data of 343 Dutch geriatric outpatients were analysed by Cox and linear regression, while adjusting for covariates. Drug groups were coded according to the Anatomical Therapeutic Chemical classification system; use was compared to non-use. Hypomagnesemia was defined as plasma Mg < 0.75 mmol/l and <0.70 mmol/l. RESULTS: Prevalence of hypomagnesemia was 22.2% (Mg < 0.75 mmol/l) or 12.2% (Mg < 0.70 mmol/l); 67.6% of the patients used ≥5 medications (polypharmacy). The number of different drugs used was inversely linearly associated with Mg level (beta -0.01; p < 0.01). Fully adjusted Cox regression showed significant associations of polypharmacy with hypomagnesemia (Mg < 0.75 mmol/l) (prevalence ratio (PR) 1.81; 95%CI 1.08-3.14), proton pump inhibitors (PR 1.80; 95%CI 1.20-2.72), and metformin (PR 2.34; 95%CI 1.56-3.50). Moreover, stratified analyses pointed towards associations with calcium supplements (PR 2.26; 95%CI 1.20-4.26), insulins (PR 3.88; 95%CI 2.19-6.86), vitamin K antagonists (PR 2.01; 95%CI 1.05-3.85), statins (PR 2.44; 95%CI 1.31-4.56), and bisphosphonates (PR 2.97; 95%CI 1.65-5.36) in patients <80 years; selective beta blockers (PR 2.01; 95%CI 1.19-3.40) if BMI <27.0 kg/m2; and adrenergic inhalants in male users (PR 3.62; 95%CI 1.73-7.56). Linear regression supported these associations. CONCLUSION: As polypharmacy and several medications are associated with hypomagnesemia, Mg merits more attention, particularly in diabetes, cardiovascular disease, and in side-effects of proton pump inhibitors and calcium supplements.

Feeding mitochondria: Potential role of nutritional components to improve critical illness convalescence.

Persistent physical impairment is frequently encountered after critical illness. Recent data point towards mitochondrial dysfunction as an important determinant of this phenomenon. This narrative review provides a comprehensive overview of the present knowledge of mitochondrial function during and after critical illness and the role and potential therapeutic applications of specific micronutrients to restore mitochondrial function. Increased lactate levels and decreased mitochondrial ATP-production are common findings during critical illness and considered to be associated with decreased activity of muscle mitochondrial complexes in the electron transfer system. Adequate nutrient levels are essential for mitochondrial function as several specific micronutrients play crucial roles in energy metabolism and ATP-production. We have addressed the role of B vitamins, ascorbic acid, α-tocopherol, selenium, zinc, coenzyme Q10, caffeine, melatonin, carnitine, nitrate, lipoic acid and taurine in mitochondrial function. B vitamins and lipoic acid are essential in the tricarboxylic acid cycle, while selenium, α-tocopherol, Coenzyme Q10, caffeine, and melatonin are suggested to boost the electron transfer system function. Carnitine is essential for fatty acid beta-oxidation. Selenium is involved in mitochondrial biogenesis. Notwithstanding the documented importance of several nutritional components for optimal mitochondrial function, at present, there are no studies providing directions for optimal requirements during or after critical illness although deficiencies of these specific micronutrients involved in mitochondrial metabolism are common. Considering the interplay between these specific micronutrients, future research should pay more attention to their combined supply to provide guidance for use in clinical practise. REVISION NUMBER: YCLNU-D-17-01092R2.

Ionized and Total Magnesium Levels Change during Repeated Exercise in Older Adults.

BACKGROUND: Magnesium is essential for health and performance. Sub-optimal levels have been reported for older persons. In addition, physical exercise is known to temporally decrease magnesium blood concentrations. OBJECTIVE: To investigate these observations in conjunction we assessed total (tMg) and ionized magnesium (iMg) concentrations in plasma and whole blood, respectively, during 4 consecutive days of exercise in very old vital adults. DESIGN: 68 participants (age 83.7±1.9 years) were monitored on 4 consecutive days at which they walked 30-40km (average ~8 hours) per day at a self-determined pace. Blood samples were collected one or two days prior to the start of exercise (baseline) and every walking day immediately post-exercise. Samples were analysed for tMg and iMg levels. RESULTS: Baseline tMg and iMg levels were 0.85±0.07 and 0.47±0.07 mmol/L, respectively. iMg decreased after the first walking day (-0.10±0.09 mmol/L, p<.001), increased after the second (+0.11±0.07 mmol/L, p<.001), was unchanged after the third and decreased on the final walking day, all compared to the previous day. tMg was only higher after the third walking day compared to the second walking day (p=.012). In 88% of the participants, iMg levels reached values considered to be sub-optimal at day 1, in 16% of the participants values were sub-optimal for tMg at day 2. CONCLUSION: Prolonged moderate intensity exercise caused acute effects on iMg levels in a degree comparable to that after a bout of intensive exercise. These effects were not associated with drop-out or health problems. After the second consecutive day of exercise, levels were returned to baseline values, suggesting rapid adaptation/resilience in this population.

Hypothalamic inflammation and food intake regulation during chronic illness.

Anorexia is a common symptom in chronic illness. It contributes to malnutrition and strongly affects survival and quality of life. A common denominator of many chronic diseases is an elevated inflammatory status, which is considered to play a pivotal role in the failure of food-intake regulating systems in the hypothalamus. In this review, we summarize findings on the role of hypothalamic inflammation on food intake regulation involving hypothalamic neuropeptide Y (NPY) and pro-opiomelanocortin (POMC). Furthermore, we outline the role of serotonin in the inability of these peptide based food-intake regulating systems to respond and adapt to changes in energy metabolism during chronic disease.

Moderate alcohol consumption after a mental stressor attenuates the endocrine stress response.

Alcohol is often consumed to reduce tension and improve mood when exposed to stressful situations. Previous studies showed that moderate alcohol consumption may reduce stress when alcohol is consumed prior to a stressor, but data on the effect of alcohol consumption after a mental stressor is limited. Therefore, our objective was to study whether moderate alcohol consumption immediately after a mental stressor attenuates the stress response. Twenty-four healthy men (age 21-40 y, BMI 18-27 kg/m2) participated in a placebo-controlled trial. They randomly consumed 2 cans (660 mL, ∼26 g alcohol) of beer or alcohol-free beer immediately after a mental stressor (Stroop task and Trier Social Stress Test). Physiological and immunological stress response was measured by monitoring heart rate and repeated measures of the hypothalamic-pituitary-adrenal axis (HPA-axis), white blood cells and a set of cytokines. After a mental stressor, cortisol and adrenocorticotropic hormone (ACTH) concentrations were 100% and 176% more reduced at 60 min (P = 0.012 and P = 0.001, respectively) and 92% and 60% more reduced at 90 min (P < 0.001 and P = 0.056, respectively) after beer consumption as compared to alcohol-free beer consumption. Heart rate and dehydroepiandrosterone (DHEA) were not influenced by alcohol consumption. Plasma IL-8 concentrations remained lower during the stress recovery period after beer consumption than after alcohol-free beer consumption (P < 0.001). In conclusion, consumption of a moderate dose of alcohol after a mental stressor may facilitate recovery of the endocrine stress response as reflected by decreasing plasma ACTH and cortisol.

Differences in food intake of tumour-bearing cachectic mice are associated with hypothalamic serotonin signalling.

BACKGROUND: Anorexia is a common symptom among cancer patients and contributes to malnutrition and strongly impinges on quality of life. Cancer-induced anorexia is thought to be caused by an inability of food intake-regulating systems in the hypothalamus to respond adequately to negative energy balance during tumour growth. Here, we show that this impaired response of food-intake control is likely to be mediated by altered serotonin signalling and by failure in post-transcriptional neuropeptide Y (NPY) regulation. METHODS: Two tumour cachectic mouse models with different food intake behaviours were used: a C26-colon adenocarcinoma model with increased food intake and a Lewis lung carcinoma model with decreased food intake. This contrast in food intake behaviour between tumour-bearing (TB) mice in response to growth of the two different tumours was used to distinguish between processes involved in cachexia and mechanisms that might be important in food intake regulation. The hypothalamus was used for transcriptomics (affymetrix chips). RESULTS: In both models, hypothalamic expression of orexigenic NPY was significantly higher compared with controls, suggesting that this change does not directly reflect food intake status but might be linked to negative energy balance in cachexia. Expression of genes involved in serotonin signalling showed to be different between C26-TB mice and Lewis lung carcinoma-TB mice and was inversely associated with food intake. In vitro, using hypothalamic cell lines, serotonin repressed neuronal hypothalamic NPY secretion while not affecting messenger NPY expression, suggesting that serotonin signalling can interfere with NPY synthesis, transport, or secretion. CONCLUSIONS: Altered serotonin signalling is associated with changes in food intake behaviour in cachectic TB mice. Serotonins' inhibitory effect on food intake under cancer cachectic conditions is probably via affecting the NPY system. Therefore, serotonin regulation might be a therapeutic target to prevent the development of cancer-induced eating disorders.

Cholecystokinin regulates satiation independently of the abdominal vagal nerve in a pig model of total subdiaphragmatic vagotomy.

The vagal nerve and gut hormones CCK and GLP-1 play important roles in the control of food intake. However, it is not clear to what extent CCK and GLP-1 increase satiation by stimulating receptors located on abdominal vagal nerve endings or via receptors located elsewhere. This study aimed to further explore the relative contribution of the abdominal vagal nerve in mediating the satiating effects of endogenous CCK and GLP-1. Total subdiaphragmatic vagotomy or sham operation was combined with administration of CCK1 and GLP-1 receptor antagonists devazepide and exendin (9-39) in 12 pigs, applying an unbalanced Latin Square within-subject design. Furthermore, effects of vagotomy on preprandial and postprandial acetaminophen absorption, glucose, insulin, GLP-1 and CCK plasma concentrations were investigated. Ad libitum liquid meal intake (mean±SEM) was similar in sham and vagotomized pigs (4180±435 and 3760±810 g/meal). Intake increased by about 20% after blockade of CCK1 receptors, independently of the abdominal vagal nerve. Food intake did not increase after blockade of GLP-1 receptors. Blockade of CCK1 and GLP-1 receptors increased circulating CCK and GLP-1 concentrations in sham pigs only, suggesting the existence of a vagal reflex mechanism in the regulation of plasma CCK1 and GLP-1 concentrations. Vagotomy decreased acetaminophen absorption and changed glucose, insulin, CCK and GLP-1 concentrations indicating a delay in gastric emptying. Our data show that at liquid feeding, satiation is decreased effectively by pharmacological blockade of CCK1 receptors. We conclude that regulation of liquid meal intake appears to be primarily regulated by CCK1 receptors not located on abdominal vagal nerve endings.

The regulation of oxidative drug metabolism by growth hormone in the dwarf goat: differences from and similarities to the mechanisms in rats.

The effects of bovine GH (BST), administered in different dose patterns, on in-vivo oxidative drug metabolism, were studied in female dwarf goats. Animals received recombinantly derived methionyl BST at a dose of 500 micrograms/kg body weight per 24 h for 6 days. It was administered to one group of goats as one s.c. injection per day, another group received a similar 24-h dose divided into three s.c. injections given at 8-h intervals, and the third group received 50 micrograms BST/kg body weight every 2.5 h by a pulsative i.v. infusion. Oxidative metabolic capacity was assessed by determining plasma sulphadimidine (SDD) elimination and urinary metabolite excretion. SDD shows a marked sex-dependent plasma elimination in dwarf goats, with male goats having a lower plasma clearance than female goats. When BST was given by daily injection, no clear effects on SDD plasma clearance or urinary metabolite excretion were observed. However, when the total dose was divided into three injections given at 8-h intervals, the plasma SDD elimination rate decreased. This was associated with a decrease in urinary excretion of the two main hydroxy SDD metabolites. When BST was given by discontinuous i.v. infusion, simulating the male endogenous plasma GH pattern, a marked decrease in SDD plasma clearance was observed. In addition, the excretion of the two urinary hydroxy metabolites was considerably reduced. These results suggest that GH can affect drug oxidation in dwarf goats via mechanisms similar to those suggested for rats. However, in the dwarf goat, the sex differences in drug metabolism are opposite to those in rats.

Tiamulin inhibits human CYP3A4 activity in an NIH/3T3 cell line stably expressing CYP3A4 cDNA.

Tiamulin is an antibiotic frequently used in veterinary medicine. The drug has been shown to produce clinically important interactions with other compounds that are administered simultaneously. An NIH/3T3 cell line, stably expressing human cytochrome P450 (EC 1.14.14.1) cDNA (CYP3A4), was used to study the effect of tiamulin on CYP3A4 activity. The 6 beta-hydroxylation activity of testosterone, which is increased in CYP3A4-expressing cells compared to vector-transfected cells, showed reduced activity after incubation with 1 microM tiamulin and was completely reduced to background level after incubation with 2, 5 and 10 microM tiamulin. The CYP3A4-expressing cell line was used in combination with a shuttle vector containing the bacterial lacZ' gene to study the effect of tiamulin on CYP3A4-mediated mutagenicity of aflatoxin B1. The mutation frequency of aflatoxin B1 could be completely inhibited by tiamulin in CYP3A4-expressing cells, but no effect was observed on the mutation frequency of the direct mutagen ethylmethanesulphonate. Western blotting of homogenates of the CYP3A4-expressing cell line showed stabilization of CYP3A4 protein after incubation with tiamulin, supporting the hypothesis that the mechanism of inhibition is by binding of tiamulin to the cytochrome.

Differential effects of pentoxifylline on the hepatic inflammatory response in porcine liver cell cultures. Increase in inducible nitric oxide synthase expression.

Pentoxifylline (PTX) has been shown to exert hepatoprotective effects in various liver injury models. However, little information is available about the effect of PTX on the hepatic acute phase response. In the present study, the effect of PTX on a lipopolysaccharide (LPS)-induced acute phase response in primary porcine liver cell cultures was examined. During 72 hr of incubation with or without LPS, the ability of PTX to influence the secretion of tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), acute phase proteins, and nitric oxide (NO) was assessed. PTX completely inhibited LPS-induced TNF-alpha production and attenuated IL-6 only after 48 hr of incubation. In contrast, PTX potentiated NO production and the expression of inducible nitric oxide synthase (iNOS) in hepatocytes after stimulation with LPS. The increased expression of iNOS and concurrent production of NO was also observed when liver cell cultures were incubated with dibutyryl cyclic adenosine monophosphate. No effect of PTX on acute phase protein secretion was observed during 72 hr of incubation. The present results show that PTX differentially affects the endotoxin-induced inflammatory response in primary porcine liver cell cultures by suppressing TNF-alpha and IL-6 while potentiating NO production.

Differential effect of pentoxifylline on lipopolysaccharide-induced downregulation of cytochrome P450.

It is now established that inflammatory stimuli such as lipopolysaccharides (LPS) and polyinosinic acid:polycytidylic (polyIC) suppress hepatic expression of cytochrome P450 (P450) genes in rat liver. Previous studies have suggested that LPS- or polyIC-induced downregulation of P450 was due to endogenously released inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1, interleukin-6, and interferons (IFNs). To improve our understanding of the role of inflammatory cytokines in mediating P450 depression, we investigated the possibility of preventing P450 downregulation with pentoxifylline. Pentoxifylline has been shown to inhibit LPS-induced TNF-alpha production by suppression of TNF-alpha gene expression. The present study shows that in uninduced male rats pentoxifylline selectively prevents the downregulation of microsomal P4501A2 and P4502B caused by LPS. No protective effect of pentoxifylline on the downregulation of P4502E1 and P4503A1/2 was observed. PolyIC-induced downregulation of P4501A2, P4502B, P4502E1, and P4503A1/2 was not affected by pentoxifylline. These results suggest that the LPS-induced downregulation of P4501A2 and P4502B is mediated to a large extent by TNF-alpha. Other cytokines might be involved in the suppression of P4502E1 and P4503A1/2. The fact that polyIC-induced downregulation is not protected by pentoxifylline is further evidence that this agent acts via a selective induction of IFNs.

Stereoselectivity at the beta2-adrenoceptor on macrophages is a major determinant of the anti-inflammatory effects of beta2-agonists.

Previous research has shown that beta-adrenoceptor (beta-AR) agonists have potent anti-inflammatory capabilities, e.g. represented by suppression of release of the proinflammatory cytokines. Aim of this research was to determine whether the effects of beta-agonists on LPS-induced TNFalpha and IL-10 release are influenced by their different stereochemistry. In addition, the role of the beta-AR subtypes was studied. The effect of two stereoisomers of the selective beta2-AR agonist TA2005 [(R,R)- and (S,S)-] on the LPS-induced TNFalpha and IL-10 release by U937 macrophages was compared. The (R,R)-stereoisomer was 277 times more potent in inhibiting the TNFalpha release than the (S,S)-form. The (R,R)-stereoisomer also appeared to be more potent in increasing the IL-10 release. In radioligand binding studies the affinity of (R,R)-TA2005 for the beta-adrenoceptor was 755 times higher than the (S,S)-TA2005 stereoisomer. In addition, the elevation of intracellular cAMP in U937 cells appeared to be stereoselective: (R,R)-TA2005 was more potent in elevating intracellular cAMP. The effect of both stereoisomers on the LPS-induced TNFalpha release could almost completely be antagonized by preincubation with the selective beta2-AR-antagonist ICI-118551. Further evidence that the effect of the beta-agonists is mediated via the beta2-adrenoceptor subtype exclusively was acquired by incubation of U937 cells with selective beta1- and beta3-agonists. None of these receptor subtype agonists showed significant suppressive effect on TNFalpha release. This study provides additional proof that the anti-inflammatory effects of beta2-agonists are mediated via the beta2-adrenoceptor and indicates that these effects are highly dependent on the stereoselectivity of the ligand.

Characterization of cytochrome P450 isoenzymes in primary cultures of pig hepatocytes.

Despite the fact that pigs are increasingly used in pharmacological and toxicological studies, knowledge on the enzymes which metabolize xenobiotics, in particular cytochrome P450 (CYP) enzymes, in pigs is still very limited. Primary cultures of pig hepatocytes were used to characterize CYP enzymes. The characterization was performed at the level of enzymatic activities, apoprotein and mRNA analyses. Enzyme inducers investigated were beta-naphthoflavone (BNF), phenobarbital (PB), dexamethasone (DEX) and rifampicin (RIF). After 48hr of BNF treatment, CYP1A protein and mRNA levels were increased, and ethoxyresorufin O-deethylation and caffeine 3-demethylation were strongly induced. PB and RIF increased the levels of CYP3A apoprotein and mRNA, whereas BNF down-regulated CYP3A and related activities. PB and RIF treatment resulted in increased ethylmorphine N-demethylation and testosterone hydroxylation, which appears to be the result of CYP3A induction. Hybridization of pig RNA with a human CYP2C9 cDNA probe showed a PB and RIF inducible CYP, which was down-regulated by BNF. Similar inducing effects were observed for tolbutamide, a marker substrate for CYP2C. DEX was not a potent inducer, although some induction of CYP3A mRNA was observed. The present results indicate the absence of CYP2B and probably CYP2D enzymes and activities in pig liver. Despite some dissimilarities, the results indicate that pigs, apart from their very human-like physiology, might represent a more appropriate model species for oxidative drug metabolism in humans than rats.

Congener specific PCB and polychlorinated camphene (toxaphene) levels in Svalbard ringed seals (Phoca hispida) in relation to sex, age, condition and cytochrome P450 enzyme activity.

Congener specific PCB and toxaphene (polychlorinated camphene, PCC) analyses were performed in seal blubber, collected in Svalbard, Norway. The concentration, body burden and metabolic index (PCB congener concentration in seal relative to their prey) were calculated. Multiple regression analyses were carried out to evaluate the influence of age, sex, blubber (as a percentage of total body weight) and cytochrome P450 activities on PCB and PCC levels. Levels of total PCBs found were five times higher than in ringed seals from the Canadian Arctic, corresponding with the relatively high contaminant levels in the European Arctic. The dominant PCB congeners (> 70% of the total PCBs measured) were 153, 138, 99, 180 and 101. The observed PCB and PCC accumulation patterns were very similar to patterns in seals from other studies, suggesting a large resemblance in contaminant metabolism. A decrease in the relative abundance of the lower chlorinated PCBs, was associated with higher concentrations of PCB 153. Since there was no indication for selective PCB excretion by lactating females, this suggests metabolism of these PCBs in ringed seals due to xenobiotic metabolising enzymes. The metabolic index confirmed the model of persistency of the different PCBs except for congener 128 and 138. These congeners, considered persistent in seals, could to some extent be metabolised in ringed seals. However, co-elution of PCB 138 with PCB 163 and of PCB 128 with TOX 50 possibly has resulted in an underestimation of the metabolic index for these congeners. Multiple regression analyses revealed a significant positive effect of age and a negative effect of the blubber content on the PCB concentrations. Since large fluctuations of body lipids occur between seasons in pinnipeds, PCB measurements should account for the total blubber content to avoid biased results. PCBs with vicinal H-atoms in the o, m or the m, p positions showed in addition a relation with cytochrome P450 enzyme activities. Surprisingly, no effect of sex on the PCB concentrations was observed, probably because female ringed seals, unlike other pinnipeds, continue feeding during lactation. This results in only small amounts of lipid and lipid-associated contaminants being mobilised from the blubber. Consequently, contaminant excretion with the milk will be low. Toxaphene concentrations found were low compared to levels found in the Canadian Arctic. Two congeners, TOX 26 and TOX 50 were predominant (15 and 18%, respectively of total toxaphene). There was no effect of sex, age, total blubber, or cytochrome P450 activities on the toxaphene levels. There was also no correlation between toxaphene and PCB levels, which may indicate differences in exposure and metabolism between these contaminants. Toxaphenes did not bioaccumulate to any substantial extent in ringed seals.

Selective changes in oxidative xenobiotic metabolism in vivo and in vitro after parenteral administration of recombinant bovine somatotrophin to rats.

Effects of recombinant bovine somatotrophin (rBST) on in vivo and in vitro oxidative drug metabolism were studied in male rats. rBST was given subcutaneously at a dose of 250 or 500 micrograms 100 g-1 bodyweight 24 h-1 in different dosage patterns. Sulphadimidine (SDD) plasma clearance, urinary excretion of 6-hydroxy-SDD and the in vitro microsomal SDD-hydroxylations were only inhibited when rBST was given in three injections per 24 hours. The hepatic microsomal ethylmorphine N-demethylation rate and the testosterone hydroxylation rate at the 6 beta position were significantly reduced after one rBST injection per 24 hours. Microsomal testosterone hydroxylation rates at the 16 alpha and 2 alpha-positions were reduced depending on the frequency of rBST administration. It is concluded that the inhibition of in vivo and in vitro drug oxidation in rats by rBST is associated with selective changes in activity of cytochrome P450 enzymes in the liver.

Oral bioavailability and pharmacokinetics of baquiloprim in dwarf goats.

The pharmacokinetics of baquiloprim at a dose of 8 mg kg-1 bodyweight were determined after its intravenous and intra-ruminal administration to seven healthy female dwarf goats. After intravenous injection, the plasma elimination curve showed a rapid distribution phase (mean [SD] t1/2 alpha 0.89 [0.4] hours). The mean volume of distribution at steady-state (Vdss) was 14.1 (2.7) litres kg-1 bodyweight. The mean elimination half-life (t1/2 beta) was 14.0 (2.3) hours. After intra-ruminal administration its maximum concentration in plasma (Cmax) was 0.09 (0.01 microgram ml-1 and this maximum was not reached until approximately 35 hours after administration. The systemic oral bioavailability, calculated up to 48 hours after dosing, was 33.7 (7.1) per cent. Owing to a prolonged absorption phase, the data from only four of the goats fitted reasonably to a compartmental model.