Catecholamine and cortisol responses of horses to incremental exertion

The responses of the plasma concentrations of catecholamines and cortisol in horses to varied relative intensities of exertion were examined. The plasma concentrations of cortisol, epinephrine and norepinephrine increased significantly (p<0.05) with exertion. The plasma cortisol concentrations at relative work intensities of 48.3%±1.4%, 82.3%±2.0% and 99.6%±0.4% of VO_2max were 114%, 124%, and 126%, respectively, of those at rest, whereas the plasma epinephrine concentrations were 239%, 772% and 3483%, and the norepinephrine concentrations were 138%, 255%, and 1121% of the values at rest. There was a significant (p<0.0001) relationship between the plasma epinephrine and norepinephrine concentrations. The blood lactate concentration and the plasma epinephrine and norepinephrine concentrations were significantly (p<0.0001) related, as were the relative work intensity (%VO_2max) and the plasma epinephrine and norepinephrine concentrations. The relationships between the plasma cortisol concentration and work intensity or blood lactate concentration were not significant (p>0.05). This study demonstrates a relationship between relative work intensity and indicators of adrenal medullary and sympathetic activity during brief exertion in horses.     

Carbohydrate metabolism and hepatic zonation in the Atlantic hagfish,Myxine glutinosa liver: effects of hormones

Viable Atlantic hagfish (Myxine glutinosa) hepatocytes were isolated from combined or separated large and small lobes and carbohydrate metabolism was studied. Cells had low levels of glycogen (16–30 μmol·g⁻¹), and low rates of total glucose production (TGP; 0–480 nmol·h⁻¹·g⁻¹ cells). Lactate flux to glucose (5.5 nmol·h⁻¹·g⁻¹) and CO₂ (76 nmol·h⁻¹·g⁻¹) was lower than reported values for teleosts, with a low percentage (30%) of the lactate carbon reaching glucose. Insulin significantly increased total glucose production and gluconeogenesis and decreased 6-phosphofructo 1-kinase (PFK-1) activities and glucose oxidation, while glucagon was without effect on any parameter studied. Forskolin significantly increased TGP. Epinephrine (Epi), norepinephrine (NEpi), isoproterenol (Iso), and phenylephrine (Phe) all decreased CO₂ production from lactate; propanolol blocked the effects of Epi, NEpi, and Iso. The large lobe, accounting for 65% of total liver mass, had a higher glycogen content and higher CO₂ production from lactate compared to the small lobe. Furthermore, enzyme activities in the large lobe were greater than in the small lobe, with the exception of glycogen phosphorylase (GPase) which exhibited smaller %a values in the large lobe. These data indicate the presence of a hormonally-responsive carbohydrate metabolism in hagfish hepatocytes, which is qualitatively and quantitatively different between the two liver lobes.     

Effects of prolonged epinephrine infusion on blood respiratory and acid-base states in the rainbow trout: Alpha and beta effects

Rainbow trout were infused continuously for 12h with epinephrine in the presence or absence of alpha-and/or beta-adrenergic blockade to characterize the specific adrenergic mechanisms involved in the control of blood acid-base status and oxygen transport capacity. Infusion of epinephrine, alone, produced a transient respiratory acidosis, as indicated by an increase in carbon dioxide tension and a decrease in whole blood pH, yet arterial oxygen tension was elevated. Red blood cell pH increased by approximately 0.2 pH units during epinephrine infusion and this increase as well as the increase in oxygen tension were prevented by pretreatment with propranolol (a beta-adrenergic antagonist). Epinephrine infusion during alpha-adrenergic blockade caused a prolonged elevation of blood carbon dioxide tension and abolished the increases in hematocrit and hemoglobin concentrations observed during epinephrine infusion alone. Infusion of the alpha-adrenergic agonists phenylephrine (an alpha₁ agonist) or clonidine (an alpha₂ agonist) caused respiratory acidosis (decreased pH, increased CO₂ tension) and a reduction in oxygen tension. Infusion of isoprenaline (a non-specific beta agonist) caused delayed increases in carbon dioxide and oxygen tensions. We speculate that the increased carbon dioxide tension observed during epinephrine infusion is a result of beta-adrenoceptor mediated inhibition of red blood cell bicarbonate dehydration and not branchial convective or diffusive adjustments. The effects of epinephrine on blood O₂ tension, content and carrying capacity are discussed with reference to the participation of alpha- and beta-adrenergic mechanisms at the gill, spleen and red blood cell.     

基于鲁米诺 高碘酸钾后化学发光测定肾上腺素

基于肾上腺素在高碘酸钾-鲁米诺碱性体系中的后化学发光反应,结合流动注射技术,建立了测定肾上腺素的流动注射-化学发光(FI(CL)方法.该方法简单、快速、灵敏,线性范围为3.0×10-5～1.2×10-4 g/L(r=0.996 9),检出限为3.0×10-7 g/L(3σ).对5.0×10-5 g/L的肾上腺素标准溶液进行11次平行测定,相对标准偏差为2.0%.将其应用于肾上腺素注射液中肾上腺素含量的测定,结果令人满意.同时,还初步探讨了该化学发光反应的发光机制.     

肾上腺素对岩牡蛎幼虫变态的诱导

为了得到壳型规则、大小均一的单体牡蛎,本研究采用肾上腺素对岩牡蛎单体苗种生产的诱导条件进行研究,阐明了岩牡蛎单体苗种的最适诱导浓度、诱导时间和诱导密度。结果显示,肾上腺素能显著诱导岩牡蛎幼虫的不固着变态,最适诱导浓度为5×10–5 mol/L,最适诱导时间为1 h,提高诱导浓度和延长诱导时间导致岩牡蛎幼虫的不固着变态率、稚贝壳高和存活率显著降低;肾上腺素对低于8个/mL幼虫密度的诱导效果差异不显著,但稚贝壳高和存活率在8个/mL的培育密度下显著低于0.5～4个/mL,研究表明利用肾上腺素诱导岩牡蛎单体时,可大批量处理眼点幼虫,但稚贝充气培养的最适培养密度应不高于4个/mL。     

Caudal epidural anesthesia in mares after bicarbonate addition to a lidocaine–epinephrine combination

Objective

To investigate the nociceptive and clinical effects of buffering a lidocaine–epinephrine solution with sodium bicarbonate in caudal epidural block in mares.

Binding and Clearance of Radioactive Adrenaline and Noradrenaline in Sheep Blood

An understanding of the conditions influencing protein binding of catecholamines (CAs) is important in studying their metabolic effects. Unfortunately, reports on plasma protein binding of CAs are scarce, conflicting and mainly performed in vitro.The aim of our in vivo and in vitro studies was to investigate binding and clearance of radioactive adrenaline (epinephrine) (³H-A), noradrenaline (norepinephrine) (³H-NA) and their metabolites in sheep blood. The time course of the radioactivity in the blood after intravenous injection of ³H-A and ³H-NA (3.7 MBq each) in 4 sheep (2 of each sex; total of 8 administrations) was determined. Blood samples were taken from the jugular vein. The highest radioactivity was observed in the first sample (5 min) following injection. Radioactivity showed a biphasic disappearance. An initial stage, in which radioactivity decreased rapidly (within 1 h) after the injection, was followed by a slow stage, lasting for up to 1 month, until background levels were reached. In vitro results indicated that NA and A were present not only in plasma (70%) but also in the erythrocytes (30%; mainly bound to haemoglobin). Sephadex G-25 gel filtration revealed that from the plasma fraction about 15% was strongly bound to proteins (mainly albumin). These results demonstrate that previous experiments in this field have overestimated the percentage of CAs bound to plasma proteins, because binding to haemoglobin was previously not known. In the future, efforts should be made to characterize the adduct products of CAs and establish an assay to determine them in vivo. If this could be achieved, it would yield a valuable tool for measuring the stress experienced for a longer period.     

神经-体液对家兔颈动脉窦压力感受性反射的试验性研究

试验在氨基甲酸乙酯麻醉的家兔上进行 ,观察乙酰胆碱与肾上腺素对颈动脉窦压力感受器反射的影响。结果如下 :①以不同浓度的乙酰胆碱灌流家兔颈动脉窦区时 ,压力感受器机能曲线向左下方移位 ,曲线最大斜率 (PS)、反射性血压下降幅度 (RD)、阈压 (TP)、平衡压 (EP)和饱和压 (SP )均呈明显的剂量依赖性 ;②肾上腺素的作用则相反 ;③再以电刺激分别刺激减压神经、减压神经中枢端、迷走神经及迷走神经外周端 ,记录其血压、心率和功率谱密度 (PSD)后加以分析。观察到电刺激减压神经使PSD高频率成分 (HF )变化不大 ,其余低频成分 (LF )、极低频成分 (VLF)及总变异 (TV)增大 (P <0 0 5)。还观察到电刺激迷走神经后对心率变异性 (HRV)的影响 ,以及对HF、LF、VLF及TV的增大显著 (P <0 0 5)。     

流动注射化学发光法测定肾上腺素

作者采用流动注射技术,对肾上腺素－高锰酸钾体系的化学发光行为,影响化学发光强度的诸因素进行了探讨,建立了化学发光法测定肾上腺素的新方法。方法的检出限为６×１０－８ｇ／ｍｌ,线性范围为１．０×１０－７－１．０×１０－５ｇ／ｍｌ。对４．０×１０－６ｇ／ｍｌ肾上腺素进行１１次平行测定,得方法的相对标准偏差为１．６％。