共查询到20条相似文献,搜索用时 15 毫秒
1.
A. A. Solovieva E. A. Sedova E. S. Tomilovskaya T. A. Shigueva B. V. Afonin 《Human physiology》2016,42(7):740-746
Ultrasound investigations (USI) of the liver, organs and vessels of the gastroduodenal area, as well as blood biochemistry, were performed in two groups of male volunteers on the 4th day of their stay in the conditions of “dry” immersion with and without the application of countermeasures, including the support load imitator (SLI) or high-frequency electromyostimulation. Using 13С-methacetin breath test (13C-MBT), two other groups were investigated for the effect of immersion on the detoxification activity and metabolic capacity of the liver and the efficacy of SLI. The performed USIs have identified deceleration in the hepatic venous flow and the signs of plethora in the abdominal venous system. Elevated blood levels were detected in pepsinogen, pancreatic amylase, bilirubin total, due to its unconjugated fraction, insulin, and C-peptide. The 13C-MBT has shown a slowdown in the rate of 13C-methacetin inactivation and a reduction in the hepatic metabolic capacity. The application of countermeasures during the immersion has not affected the ultrasound patterns of the hemodynamic rearrangement in both the liver and the abdomen. High frequency electromyostimulation during the immersion has neutralized the changes in all biochemical indicators except C-peptide, while the application of SLI has led to the restoration of only pepsinogen and amylase to the initial values. In addition, the use of SLI during the immersion counteracted the reduction in the 13C-methacetin inactivation rate and did not substantially affect the reduction in the metabolic capacity of the liver. 相似文献
2.
Lieyu ZhangXunfeng Xia Ying Zhao Beidou XiYanan Yan Xin GuoYing Xiong Jianhong Zhan 《Ecological Engineering》2011,37(11):1614-1619
The ammonium nitrogen oxidation process (ANOP) is the first and most important step for nitrogen removal in constructed wetlands (CWs). The process was investigated by observing the products generated from the ANOP in on-site aerobic systems with selective inhibition of nitrite-oxidizing bacteria (NOB) through appropriate regulation of the pH, temperature and dissolved oxygen concentrations. The effects of season, plant type and density on ANOP were also studied to determine the optimal conditions for the ANOP. Nitrite accumulation was found in the aerobic experiments and greater ammonia-oxidizing bacteria than NOB numbers, showing that partial nitrification to nitrite was occurring in the studied CWs. The nitrogen removal rate was positively linearly correlated with the nitrite accumulation rate, and so the more NH3-N removed by ANOP, the greater the resulting nitrogen removal. Season and plant density had a significant effect on the ANOP. However, there were no significant differences between the units planted with common reed and cattail. 相似文献
3.
Tuula Sinisalo Roger I. Jones Eero Helle † E. Tellervo Valtonen ‡ 《Marine Mammal Science》2008,24(1):159-170
The stable isotope ratios (δ13C and δ15N) of three tissues with different metabolic rates (plasma, liver, and muscle) were used to investigate temporal variation in diet among nine individual Baltic ringed seals (Phoca hispida botnica Gmelin) from the Bothnian Bay, northeast Baltic Sea. The isotope values from plasma should reflect the most recent diet, values from liver the diet of the past weeks prior to sampling, and values from muscle should integrate diet over almost the entire breeding season of the ringed seals. In general, δ13C values of liver were more enriched in 13C than were those of either muscle or plasma, suggesting that the diet of the seals may have included a higher proportion of 13C‐enriched benthic prey in April. Females showed more variable δ13C values than males, suggesting possible gender differences in diet or in foraging locations. The differences that were apparent between females possibly reflect individual variation in the onset and duration of parturition and lactation, both of which likely restrict female foraging. Previous data from parasite infections and from alimentary tract contents of the same seals were linked to the isotope data to assist in drawing inferences about changes in the diets of individual seals. 相似文献
4.
Knowledge gaps regarding potential ontogeny and plant species identity effects on carbon isotope fractionation might lead to misinterpretations of carbon isotope composition (δ13C) of respired CO2, a widely-used integrator of environmental conditions. In monospecific mesocosms grown under controlled conditions, the δ13C of C pools and fluxes and leaf ecophysiological parameters of seven herbaceous species belonging to three functional groups (crops, forage grasses and legumes) were investigated at three ontogenetic stages of their vegetative cycle (young foliage, maximum growth rate, early senescence). Ontogeny-related changes in δ13C of leaf- and soil-respired CO2 and 13C/12C fractionation in respiration (ΔR) were species-dependent and up to 7‰, a magnitude similar to that commonly measured in response to environmental factors. At plant and soil levels, changes in δ13C of respired CO2 and ΔR with ontogeny were related to changes in plant physiological status, likely through ontogeny-driven changes in the C sink to source strength ratio in the aboveground plant compartment. Our data further showed that lower ΔR values (i.e. respired CO2 relatively less depleted in 13C) were observed with decreasing net assimilation. Our findings highlight the importance of accounting for ontogenetic stage and plant community composition in ecological studies using stable carbon isotopes. 相似文献
5.
Bracht A Schmeisch AP Constantin J Pagadigorria CS Kelmer-Bracht AM 《Cell biology and toxicology》1999,15(4):217-227
Diltiazem causes vasoconstriction in the liver when present at high concentrations, an action that is strictly Ca2+-dependent. Diltiazem is also active on energy metabolism. This toxic action could be partly a consequence of hemodynamic effects. In the absence of Ca2+, the hemodynamic effects are no longer present and, consequently, Ca2+-free experiments are useful for distinguishing between hemodynamics-dependent and hemodynamics-independent effects. The experimental system used was the hemoglobin-free perfused rat liver from fed and fasted rats. Diltiazem was infused at various concentrations in the presence and absence of Ca2+. Several metabolic parameters were measured: lactate and pyruvate production (glycolysis), glycogenolysis, oxygen uptake, gluconeogenesis, and the cellular levels of lactate, pyruvate, glucose, AMP, ADP, and ATP. The effects of diltiazem can be divided into three groups: (1) Effects that are strictly dependent on the Ca2+-mediated hemodynamic action. This group comprises inhibition of oxygen uptake at all concentrations (50–500 mol/L) inhibition of lactate, pyruvate, and glucose release at high concentrations; the decrease in cellular ATP; the increase in cellular AMP; and the cellular accumulation of glucose and lactate. (2) Effects that are independent of the hemodynamic action. The most relevant effect of this type is inhibition of gluconeogenesis. (3) Effects that are influenced by Ca2+ but are independent of the hemodynamic effects. This is the typical case of lactate and glucose release from endogenous glycogen, whose stimulation by low diltiazem concentrations is more pronounced in the presence of Ca2+ than in its absence. 相似文献
6.
Hyun Yoo Eu-Ree Ahn Se-Jin Kim Seon-Hyeong Lee Seung Hyun Oh Soo-Youl Kim 《Amino acids》2013,44(1):189-197
Acute sepsis can be induced by cytokines such as TNF-α and biological products such as LPS. All of these agents cause systemic inflammation, which is characterized by hemodynamic shock and liver toxicity. However, the outcomes of different septic shock models were totally opposite in transglutaminase 2 knockout (TGase 2?/?) mice. The aim of our study was to clarify the role of TGase 2 in liver injury. Therefore, we explored the role of TGase 2 in liver damage using two different stress models: LPS-induced endotoxic shock and TNF-α/actinomycin D (ActD)-induced sepsis. TNF-α-dependent septic shock resulted in increased liver damage in TGase 2?/? mice compared with wild-type (WT) mice, and was accompanied by increased levels of caspase 3 and cathepsin D (CTSD) in the damaged liver. Conversely, LPS-induced septic shock resulted in ablation of inflammatory endotoxic shock in TGase 2?/? mice and decreased liver injury. We found that TGase 2 protected liver tissue from TNF-α-dependent septic shock by reducing the expression of caspase 3 and CTSD. However, TGase 2 differently participated in increased the hemodynamic shock in LPS-induced septic shock through macrophage activation rather than protecting direct liver damage. Therefore, these findings demonstrate that septic shock caused by different agents may induce different results in TGase 2?/? mice depending on the primary target organs affected. 相似文献
7.
Changes in plant inputs under changing atmospheric CO2 can be expected to alter the size and/or functional characteristics of soil microbial communities which can determine whether soils are a C sink or source. Stable isotope probing was used to trace autotrophically fixed 13C into phospholipid fatty acid (PLFA) biomarkers in Mojave Desert soils planted with the desert shrub, Larrea tridentata. Seedlings were pulse‐labeled with 13CO2 under ambient and elevated CO2 in controlled environmental growth chambers. The label was chased into the soil by extracting soil PLFAs after labeling at Days 0, 2, 10, 24, and 49. Eighteen of 29 PLFAs identified showed 13C enrichment relative to nonlabeled control soils. Patterns of PLFA enrichment varied temporally and were similar for various PLFAs found within a microbial functional group. Enrichment of PLFA 13C generally occurred within the first 2 days in general and fungal biomarkers, followed by increasingly greater enrichment in bacterial biomarkers as the study progressed (Gram‐negative, Gram‐positive, actinobacteria). While treatment CO2 level did not affect total PLFA‐C concentrations, microbial functional group abundances and distribution responded to treatment CO2 level and these shifts persisted throughout the study. Specifically, ratios of bacterial‐to‐total PLFA‐C decreased and fungal‐to‐bacterial PLFA‐C increased under elevated CO2 compared with ambient conditions. Differences in the timing of 13C incorporation into lipid biomarkers coupled with changes in microbial functional groups indicate that microbial community characteristics in Mojave Desert soils have shifted in response to long‐term exposure to increased atmospheric CO2. 相似文献
8.
J L Poyer P B McCay E K Lai E G Janzen E R Davis 《Biochemical and biophysical research communications》1980,94(4):1154-1160
Rat liver microsomal incubation systems containing the free radical spin trap, phenyl-t-butyl nitrone, as well as an NADPH generating system and [13C]CCl4 (90 atom % 13C) produce electron spin resonance spectra consistent with that expected for a trichloromethyl-phenyl-t-butyl nitrone adduct. This same spectrum is observed in a lipid extract of the liver from a rat orally administered [13C]CCl4 as well as in a solution of phenyl-t-butyl nitrone and [13C]CCl4 irradiated with ultraviolet light. 相似文献
9.
There is considerable evidence suggesting that compartmentalized functional pools of cholesterol in the liver contribute differently to the formation of bile acids as the precursor. The present paper deals with the incorporation of [1-14C]acetate and of [1,2-3H]cholesterol carried on lipoproteins (LDL and HDL) into biliary bile acids in perfused rat livers and bile-fistula rats. The results showed that endogenous cholesterol synthesized newly from [1-14C]acetate in the liver was incorporated into both cholic acid and chenodeoxycholic acid in a similar way, while exogenous lipoprotein-[1,2-3H]cholesterol delivered to hepatocytes from hepatic circulation was incorporated into chenodeoxycholic acid at a higher rate. 相似文献
10.
Stable isotope analysis indicates a lack of inter- and intra-specific dietary redundancy among ecologically important coral reef fishes 总被引:1,自引:0,他引:1
Parrotfish are critical consumers on coral reefs, mediating the balance between algae and corals, and are often categorised into three functional groups based on adult morphology and feeding behaviour. We used stable isotope analysis (δ13C, δ15N) to investigate size-related ontogenetic dietary changes in multiple species of parrotfish on coral reefs around Zanzibar. We compared signatures among species and functional groups (scrapers, excavators and browsers) as well as ontogenetic stages (immature, initial and terminal phase) within species. Stable isotope analysis suggests that ontogenetic dietary shifts occurred in seven of the nine species examined; larger individuals had enriched δ13C values, with no relationship between size and δ15N. The relationship between fish length and δ13C signature was maintained when species were categorised as scrapers and excavators, but was more pronounced for scrapers than excavators, indicating stronger ontogenetic changes. Isotopic mixing models classified the initial phase of both the most abundant excavator (Chlorurus sordidus) as a scraper and the immature stage of the scraper Scarus ghobban (the largest species) as an excavator, indicating that diet relates to size rather than taxonomy. The results indicate that parrotfish may show similar intra-group changes in diet with length, but that their trophic ecology is more complex than suggested by morphology alone. Stable isotope analyses indicate that feeding ecology may differ among species within functional groups, and according to ontogenetic stage within a species. 相似文献
11.
T. P. Shcherbakova N. E. Kotel’nikova Yu. V. Bykhovtsova 《Russian Journal of Bioorganic Chemistry》2013,39(7):686-693
Methods of wide-angle X-ray scattering (WAXS), high resolution solid-state 13C NMR, and Fourier transform IR-spectroscopy are applied to study supermolecular structures and functional compositions of lignocellulose samples of wood and grass origins and powdered celluloses (PC) obtained from them under identical hydrolysis conditions. It was shown by WAXS that the structure of cellulose I is preserved in samples of powdered celluloses, however, an increased degree of crystallinity and cross-section sizes of crystallites are observed in PC samples. Specific features of changes in the supermolecular structure of cellulose occurred after the hydrolysis, i.e., an increase in the content of cellulose Iβ in PC compared to the initial samples, are established by 13C NMR method. It was shown by means of 13C NMR and Fourier transform IR-spectroscopy that the functional chemical composition of lignocelluloses is weakly affected by the hydrolysis. The presence of residual lignin functional groups in the samples is confirmed. 相似文献
12.
Variations in the carbon isotope signature of leaf dark-respired CO2 (δ13CR) within a single night is a widely observed phenomenon. However, it is unclear whether there are plant functional type differences with regard to the amplitude of the nighttime variation in δ13CR. These differences, if present, would be important for interpreting the short-term variations in the stable carbon signature of ecosystem respiration and the partitioning of carbon fluxes. To assess the plant functional type differences relating to the magnitude of the nighttime variation in δ13CR and the respiratory apparent fractionation, we measured the δ13CR, the leaf gas exchange, and the δ13C of the respiratory substrates of 22 species present in the agricultural-pastoral zone of the Songnen Plain, northeast China. The species studied were grouped into C3 and C4 plants, trees, grasses, and herbs. A significant nocturnal shift in δ13CR was detected in 20 of the studied species, with the magnitude of the shift ranging from 1‰ to 5.8‰. The magnitude of the nighttime variation in δ13CR was strongly correlated with the daytime cumulative carbon assimilation, which suggests that variation in δ13CR were influenced, to some extent, by changes in the contribution of malate decarboxylation to total respiratory CO2 flux. There were no differences in the magnitude of the nighttime variation in δ13CR between the C3 and C4 plants, as well as among the woody plants, herbs and graminoids. Leaf respired CO2 was enriched in 13C compared to biomass, soluble carbohydrates and lipids; however the magnitude of enrichment differed between 8 pm and 4 am, which were mainly caused by the changes in δ13CR. We also detected the plant functional type differences in respiratory apparent fractionation relative to biomass at 4 am, which suggests that caution should be exercised when using the δ13C of bulk leaf material as a proxy for the δ13C of leaf-respired CO2. 相似文献
13.
葡萄膜炎是一种反复发作的炎症性疾病,可导致免疫系统功能障碍和多器官损伤.然而,葡萄膜炎是否导致肝功能损害尚不十分清楚.本文通过运用流式分析技术和激光共聚焦成像技术,研究了实验性自身免疫葡萄膜炎模型的肝脏病理和功能变化.结果显示肝损伤可出现在葡萄膜炎的炎症后期并与眼损伤程度相关.并且CD3+ CD4+ T细胞、CD3- NK1.1+ DX5- NK细胞、和CD11b+ F4/80- ly6c+ 细胞在感染的眼睛和肝脏中增加.将CD3+ CD4+ T细胞回输给炎症的小鼠后,眼睛和肝脏的病理损伤加重.此外,在炎症的小鼠中可见血管扩张,大量淋巴细胞浸润到炎症的眼和肝脏的血管周围.总之,我们的研究结果提示,肝损伤可以发生在小鼠葡萄膜炎模型中,这种损伤可能与通过外周循环浸润到肝脏的CD3+ CD4+ T细胞有关. 相似文献
14.
‘Are fish what they eat’ all year round? 总被引:4,自引:0,他引:4
Isotope turnover in muscle of ectotherms depends primarily on growth rather than on metabolic replacement. Ectotherms, such
as fish, have a discontinuous pattern of growth over the year, so the isotopic signature of muscle (δ13C and δ15N) may only reflect food consumed during periods of growth. In contrast, the liver is a regulatory tissue, with a continuous
protein turnover. Therefore, the isotopic composition of liver should respond year round to changes in the isotopic signature
of food sources. Therefore, we predicted that (1) Whitefish in Lake Geneva would have larger seasonal variation in the isotopic
variation of the liver compared to that of the muscle tissue, and (2) the isotope composition of fish muscle would reflect
a long-term image of the isotope composition of the food consumed only throughout the growth period. To test these expectations,
we compared the isotope compositions of Whitefish muscle, liver and food in a 20-month study. We found that the seasonal amplitude
of isotope variation was two to three times higher in liver compared to muscle tissue. During the autumn and winter, when
growth was limited, only the isotopic signature of liver responded to changes in the isotope composition of the food sources.
The δ13C and δ15N of muscle tissue only reflected the food consumed during the spring and summer growth period. 相似文献
15.
Kristin Scharnweber Matilda L. Andersson Fernando Chaguaceda Peter Eklv 《Ecology and evolution》2021,11(14):9804
- Stable isotopes represent a unique approach to provide insights into the ecology of organisms. δ13C and δ15N have specifically been used to obtain information on the trophic ecology and food‐web interactions. Trophic discrimination factors (TDF, Δ13C and Δ15N) describe the isotopic fractionation occurring from diet to consumer tissue, and these factors are critical for obtaining precise estimates within any application of δ13C and δ15N values. It is widely acknowledged that metabolism influences TDF, being responsible for different TDF between tissues of variable metabolic activity (e.g., liver vs. muscle tissue) or species body size (small vs. large). However, the connection between the variation of metabolism occurring within a single species during its ontogeny and TDF has rarely been considered.
- Here, we conducted a 9‐month feeding experiment to report Δ13C and Δ15N of muscle and liver tissues for several weight classes of Eurasian perch (Perca fluviatilis), a widespread teleost often studied using stable isotopes, but without established TDF for feeding on a natural diet. In addition, we assessed the relationship between the standard metabolic rate (SMR) and TDF by measuring the oxygen consumption of the individuals.
- Our results showed a significant negative relationship of SMR with Δ13C, and a significant positive relationship of SMR with Δ15N of muscle tissue, but not with TDF of liver tissue. SMR varies inversely with size, which translated into a significantly different TDF of muscle tissue between size classes.
- In summary, our results emphasize the role of metabolism in shaping‐specific TDF (i.e., Δ13C and Δ15N of muscle tissue) and especially highlight the substantial differences between individuals of different ontogenetic stages within a species. Our findings thus have direct implications for the use of stable isotope data and the applications of stable isotopes in food‐web studies.
16.
17.
Daniel J. Madigan Steven Y. Litvin Brian N. Popp Aaron B. Carlisle Charles J. Farwell Barbara A. Block 《PloS one》2012,7(11)
Stable isotope analysis (SIA) of highly migratory marine pelagic animals can improve understanding of their migratory patterns and trophic ecology. However, accurate interpretation of isotopic analyses relies on knowledge of isotope turnover rates and tissue-diet isotope discrimination factors. Laboratory-derived turnover rates and discrimination factors have been difficult to obtain due to the challenges of maintaining these species in captivity. We conducted a study to determine tissue- (white muscle and liver) and isotope- (nitrogen and carbon) specific turnover rates and trophic discrimination factors (TDFs) using archived tissues from captive Pacific bluefin tuna (PBFT), Thunnus orientalis, 1–2914 days after a diet shift in captivity. Half-life values for 15N turnover in white muscle and liver were 167 and 86 days, and for 13C were 255 and 162 days, respectively. TDFs for white muscle and liver were 1.9 and 1.1‰ for δ
15N and 1.8 and 1.2‰ for δ
13C, respectively. Our results demonstrate that turnover of 15N and 13C in bluefin tuna tissues is well described by a single compartment first-order kinetics model. We report variability in turnover rates between tissue types and their isotope dynamics, and hypothesize that metabolic processes play a large role in turnover of nitrogen and carbon in PBFT white muscle and liver tissues. 15N in white muscle tissue showed the most predictable change with diet over time, suggesting that white muscle δ
15N data may provide the most reliable inferences for diet and migration studies using stable isotopes in wild fish. These results allow more accurate interpretation of field data and dramatically improve our ability to use stable isotope data from wild tunas to better understand their migration patterns and trophic ecology. 相似文献
18.
K. Blue Pahl David J. Yurkowski Sabine P. Wintner Geremy Cliff Matthew L. Dicken Nigel E. Hussey 《Journal of fish biology》2021,98(3):829-841
Stable-isotope analysis (SIA) provides a valuable tool to address complex questions pertaining to elasmobranch ecology. Liver, a metabolically active, high turnover tissue (~166 days for 95% turnover), has the potential to reveal novel insights into recent feeding/movement behaviours of this diverse group. To date, limited work has used this tissue, but ecological application of SIA in liver requires consideration of tissue preparation techniques given the potential for high concentrations of urea and lipid that could bias δ13C and δ15N values (i.e., result in artificially lower δ13C and δ15N values). Here we investigated the effectiveness of (a) deionized water washing (WW) for urea removal from liver tissue and (b) chloroform-methanol for extraction of lipids from this lipid rich tissue. We then (a) established C:N thresholds for deriving ecologically relevant liver isotopic values given complications of removing all lipid and (b) undertook a preliminary comparison of δ13C values between tissue pairs (muscle and liver) to test if observed isotopic differences correlated with known movement behaviour. Tests were conducted on four large shark species: the dusky (DUS, Carcharhinus obscurus), sand tiger (RAG, Carcharias taurus), scalloped hammerhead (SCA, Sphyrna lewini) and white shark (GRE, Carcharodon carcharias). There was no significant difference in δ15N values between lipid-extracted (LE) liver and lipid-extracted/water washed (WW) treatments, however, WW resulted in significant increases in %N, δ13C and %C. Following lipid extraction (repeated three times), some samples were still biased by lipids. Our species-specific “C:N thresholds” provide a method to derive ecologically viable isotope data given the complexities of this lipid rich tissue (C:N thresholds of 4.0, 3.6, 4.7 and 3.9 for DUS, RAG, SCA and GRE liverLEWW tissue, respectively). The preliminary comparison of C:N threshold corrected liver and muscle δ13C values corresponded with movement/habitat behaviours for each shark; minor differences in δ13C values were observed for known regional movements of DUS and RAG (δ13CDiffs = 0.24 ± 0.99‰ and 0.57 ± 0.38‰, respectively), while SCA and GRE showed greater differences (1.24 ± 0.63‰ and 1.08 ± 0.71‰, respectively) correlated to large-scale movements between temperate/tropical and pelagic/coastal environments. These data provide an approach for the successful application of liver δ13C and δ15N values to examine elasmobranch ecology. 相似文献
19.
Richard D. Beger Deborah K. Hansen Laura K. Schnackenberg Brandie M. Cross Javad J. Fatollahi F. Tracy Lagunero Zoltan Sarnyai Laszlo G. Boros 《Metabolomics : Official journal of the Metabolomic Society》2009,5(3):336-345
Previous genetic and proteomic studies identified altered activity of various enzymes such as those of fatty acid metabolism
and glycogen synthesis after a single toxic dose of valproic acid (VPA) in rats. In this study, we demonstrate the effect
of VPA on metabolite synthesis flux rates and the possible use of abnormal 13C labeled glucose-derived metabolites in plasma or urine as early markers of toxicity. Female CD-1 mice were injected subcutaneously
with saline or 600 mg/kg) VPA. Twelve hours later, the mice were injected with an intraperitoneal load of 1 g/kg [U-13C]-d-glucose. 13C isotopomers of glycogen glucose and RNA ribose in liver, kidney and brain tissue, as well as glucose disposal via cholesterol
and glucose in the plasma and urine were determined. The levels of all of the positional 13C isotopomers of glucose were similar in plasma, suggesting that a single VPA dose does not disturb glucose absorption, uptake
or hepatic glucose metabolism. Three-hour urine samples showed an increase in the injected tracer indicating a decreased glucose
re-absorption via kidney tubules. 13C labeled glucose deposited as liver glycogen or as ribose of RNA were decreased by VPA treatment; incorporation of 13C via acetyl-CoA into plasma cholesterol was significantly lower at 60 min. The severe decreases in glucose-derived carbon
flux into plasma and kidney-bound cholesterol, liver glycogen and RNA ribose synthesis, as well as decreased glucose re-absorption
and an increased disposal via urine all serve as early flux markers of VPA-induced adverse metabolic effects in the host. 相似文献
20.
Andrea Luiza de Oliveira Jurandir Fernando Comar Anacharis Babeto de Sá-Nakanishi Rosane Marina Peralta Adelar Bracht 《Molecular and cellular biochemistry》2014,388(1-2):135-147
Citrus aurantium extracts, which contain large amounts of p-synephrine, are widely used for weight loss purposes and as appetite suppressants. In the liver, C. aurantium (bitter orange) extracts affect hemodynamics, carbohydrate metabolism, and oxygen uptake. The purpose of the present work was to quantify the action of p-synephrine and also to obtain indications about its mechanism of action, a task that would be difficult to accomplish with C. aurantium extracts due to their rather complex composition. The experimental system was the isolated perfused rat liver. p-Synephrine significantly stimulated glycogenolysis, glycolysis, gluconeogenesis, and oxygen uptake. The compound also increased the portal perfusion pressure and the redox state of the cytosolic NAD+/NADH couple. A Ca2+-dependency for both the hemodynamic and the metabolic effects of p-synephrine was found. p-Synephrine stimulated both cAMP overflow and the initial Ca2+ release from the cellular stores previously labeled with 45Ca2+. The metabolic and hemodynamic actions of p-synephrine were strongly inhibited by α-adrenergic antagonists and moderately affected by β-adrenergic antagonists. The results allow to conclude that p-synephrine presents important metabolic and hemodynamic effects in the liver. These effects can be considered as both catabolic (glycogenolysis) and anabolic (gluconeogenesis), they are mediated by both α- and β-adrenergic signaling, require the simultaneous participation of both Ca2+ and cAMP, and could be contributing to the overall stimulation of metabolism that usually occurs during weight loss periods. 相似文献