Research progress in the endothelium derived hyperpolarizing factor

Until now, although the molecule of EDHF has not been cloned,some characteristics of EDHF has been clarified by scientists. It is different from NO and prostacyclin, and it is considered to play an important role in the regulat ion of vascular tone by stimulat ing the channels of K⁺ and Ca²⁺.     

Changes of potassium channels in thoracic aorta of streptozotocin-induced diabetic mice in early stage

AIM:To investigate the changes of potassium channels in thoracic aorta of streptozotocin-induced diabetic mouse in the early stage of diabetes mellitus.METHODS:The effects of 60 mmol/L KCl, phenylephrine (PE), sodium nitroprusside (SNP) were measured and concentration-response curves to SNP were determined in the presence and in the absence of the inhibitors of potassium channels on the thoracic aortic rings of diabetic and age-matched control mice in vitro. RESULTS:STZ-diabetic mice showed a significant increase in the maximum contractile response and sensitivity of thoracic aorta to 60 mmol/L KCl and PE. The endothelium-independent relaxation response to SNP was increased by diabetes and were decreased significantly by pretreatment of the vessels with 1 mmol/L tetraethylammonium (TEA), 1 mmol/L 4-aminopyridine (4-AP) and 10 μmol/L glibenclamide in diabetes thoracic aorta. Only 4-AP decreased relaxation response to SNP in age-matched control mice. The -logIC₅₀ difference of TEA in thoracic aorta rings of diabetes was significantly higher than age-matched control mice.CONCLUSION:In early stage of diabetes mellitus, the opening or expression of K_Ca channels is significantly enhanced.The opening of K_ATP channels is also enhanced in this stage.     

钾素水平对基质栽培网纹甜瓜光合及品质的影响

 在基质栽培条件下，营养液中240 mg·L^-1的钾素水平显著提高了叶片的净光合速率、果实的总糖、鲜味氨基酸、甜味氨基酸以及醋酸盐类香气组分 —戊基醋酸盐、丁基醋酸盐等的含量，改善了品质，但对产量无显著影响。在本试验范围内，过低或过高的钾素水平导致的叶片净光合速率下降是非气孔限制因素造成的。     

Pharmacokinetics of potassium bromide in adult horses

OBJECTIVE: To determine the pharmacokinetics of potassium bromide (KBr) in horses after a single and multiple oral doses. ANIMALS: Twelve adult Standardbred and Thoroughbred mares. PROCEDURE: Horses were randomly assigned into two treatment groups. In Part 1 of the study, horses were given a single oral dose of 120 mg/kg KBr. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of bromide were determined by colorimetric spectrophotometry following drug administration to permit determination of concentration versus time curves from which pharmacokinetic parameters could be calculated. Treated horses were monitored twice daily by clinical examination. Serum concentrations of sodium, potassium and chloride ions and partial pressures of venous blood gases were determined. RESULTS: Maximum mean serum bromide concentration following a single dose of KBr (120 mg/kg) was 284 +/- 15 microg/mL and the mean elimination half-life was 75 +/- 14 h. Repeated administration of a loading dose of KBr (120 mg/kg once daily for 5 days) gave a maximum serum bromide concentration of 1098 +/- 105 microg/mL. The administration of lower, maintenance doses of KBr (40 mg/kg once daily) was associated with decreased serum bromide concentrations, which plateaued at approximately 700 microg/mL. Administration of KBr was associated with significant but transient changes in serum potassium and sodium concentrations, and possible changes in base excess and plasma bicarbonate concentrations. High serum concentrations of bromide were associated with an apparent increase in serum chloride concentrations, when measured on an ion specific electrode. CONCLUSIONS AND CLINICAL RELEVANCE: A loading dose of 120 mg/kg daily over 5 days and maintenance doses of approximately 90-100 mg/kg of KBr administered once daily are predicted to result in serum bromide concentrations consistent with therapeutic efficacy for the management of seizures in other species. The clinical efficacy of this agent as an anticonvulsant medication and/or calmative in horses warrants further investigation.     

Role of mitochondrial KATP channels in cardioprotection of hyperpolarized cardioplegia

AIM:To study the protective effect of hyperpolarized cardioplegic arrest on reperfused rat heart performance and to investigate the role of mitochondrial ATP-sensitive K+ channels (mitoKATP) opening in the protection of hyperpolarized cardioplegia against ischemia/reperfusion damage. METHODS:Forty Sprague-Dawley rats were randomized into five groups (n=8 in each group): control group (Con); depolarized arrest group (D); hyperpolarized arrest group (H); depolarized cardioplegia with 5-hydroxydecanoate (5-HD) group (5HD+D); hyperpolarized cardioplegia with 5-HD group (5HD+H). The rat hearts were quickly removed to Langendorff apparatus. The heart perfusion was performed for 20 min with 37 ℃ Krebs-Henseleit buffer balanced with gas mixture (O2∶〖KG-*2〗CO2=95%∶〖KG-*2〗5%) at 5.8 kPa perfusion pressure, then cardial arrest was induced by different cardioplegic solution. Hearts were subjected to ischemia at 37 ℃ for 40 min followed by 30 min reperfusion. (1) The hemodynamics was detected at recovery after 30 min reperfusion. (2) Before ischemia and at the end-reperfusion, tissue was harvested for mitochondrial isolation and ultrastructure was observed by transmission electron microscopy (TEM). (3) Production of reactive oxygen species (ROS) was also determined at different time points. RESULTS:(1) Compared with end-equilibration, 30 min reperfusion caused significant differences in left ventricular developed pressure (LADP), left ventricular end-diastolic pressure (LVEDP), double product (DP), heart rate (HR), coronary flow (CF) (P<0.01). TEM showed that the ultrastructures of myocardial and mitochondrial were damaged remarkably. (2) When H group was compared with D, 5HD+H and Con group, significant differences were found in LVDP, LVEDP, DP, HR and CF (P<0.01). TEM showed that the myocardial and mitochondrial ultrastructures were improved remarkably. (3) The rate of ROS generating was lower in group H than that in other four groups at end-reperfusion (P<0.01). CONCLUSION:(1) Of the four cardioplegias, hyperpolarized cardioplegia is superior to improve myocardial performance, attenuates myocardial and mitochondrial injury, and reduces rate of ROS generating. (2) Mitochondrial preservation is one of mechanisms of myocardial protection in hyperpolarized cardioplegia, opening of mitoKATP enhances cardioprotection through decreasing ROS generating, providing better energe supply for reperfused myocardium.     

施肥对三种切花百合钾素吸收动态的影响

通过盆栽土培试验方法,研究了施肥与不施肥(对照)条件下东方百合、麝香百合和亚洲百合3个切花百合品种的钾素吸收规律.结果表明:随着生育期进展,各品种的切花百合地上部各器官含钾量均逐渐降低,地下部器官根和鳞茎则依品种和施肥的不同而表现出差异.鳞茎中的钾素支撑切花百合的前期地上部生长的钾素需求,经历的时间3个品种基本一致,均为47 d.钾素快速吸收期品种之间存在差异,东方百合由花芽分化至切花,历时81 d;麝香百合由花芽分化至切花,历时50 d;由亚洲百合10月6日至切花,历时25 d.施肥均提高了3个品种后期整株的钾积累量,但出现时期因品种而不同,东方百合最早、麝香百合次之、亚洲百合最迟.     

不同钾、钙、镁水平对厚皮甜瓜产量和品质的影响

利用营养液进行盆栽试验,研究不同钾、钙、镁水平对厚皮甜瓜产量和品质的影响.结果表明:钾490 mg/L、钙206 mg/L、镁65 mg/L的试验处理能显著促进厚皮甜瓜生长发育,提高果实的产量和品质,而低钾(30 mg/L)、低钙(10 mg/L)、低镬(5 mg/L)的各试验处理都明显延缓了厚皮甜瓜的生长发育,降低了果实的产量和品质.     

Role of prostaglandins,nitric oxide and potassium channel in the blunting of hypoxic pulmonary vasoconstriction in the high altitude adaptive animal

AIM: To investigate the possible role of prostaglandin, NO and potassium channel in the adaptive blunting of hypoxic pulmonary vasoconstriction (HPV) in high altitude animal (pika). METHODS: The effect of L-NAME, indomethacin and 4-AP on the response of isolated lung strips of pika and Wistar rats instead of pulmonary artery to acute hypoxia were studied. RESULTS: (1) After inhibition of prostaglandins by indomethacin, the percentage increase in hypoxic constriction in lung tissue strip of pikas was greater than that in Wistar rats , P＜0.05; (2) After inhibition of NO synthesis by L-NAME, the percentage increase in hypoxic constriction in lung tissue strip of pikas was greater than that in Wistar rats , P＜0.05; (3) After administration of 4-AP, there was no significant difference in the percentage decrease in hypoxic constriction of lung tissue strip between pika and Wistar rat. CONCLUSIONS: (1) Prostaglandins and NO might modulate HPV in either rat of pika; the closure of Voltage-gated K⁺ channels might mediate HPV in either rat or pika. (2) Prostaglandins and NO might play an important role in the blunting of HPV in pika, Voltage-gated K⁺ channels may play a minor role in the blunting of hypoxic pulmonary vasoconstriction in pika.     

干旱胁迫下钾肥对甘薯产量形成及钾素分配利用的影响

旨在研究干旱胁迫下钾肥对甘薯不同时期生长发育、产量和钾素分配利用的影响,以食用型甘薯品种‘泰中6号’为材料,以硫酸钾(K2SO4)为供试肥料,水分处理设正常灌水(W1)和干旱处理(W0),分别为土壤最大持水量的60%~70%和30%~40%;钾肥(K2O)施用量分别为0g/m~2(K0)、12g/m~2(K1)、24g/m~2(K2)和36g/m~2(K3)4个水平,测定茎叶生长指标、光合势、块根膨大速率、干物质质量分数、产量和钾素质量分数等。结果表明,施钾可以促进甘薯茎叶生长和产量提高,随着施钾量的增加,正常灌水下,甘薯茎叶生长指标、结薯数和产量在K2和K3处理均高于K1;而干旱胁迫下K2和K1处理均高于K3。正常灌水下甘薯光合势和块根膨大速率随施钾量的增加而增大,最大为K3处理,干旱胁迫下最大为K2处理。干旱胁迫下甘薯植株地上部器官中钾质量分数均高于正常灌水,块根中相反,且甘薯钾肥利用率显著低于正常灌水。干旱胁迫下施钾有利于甘薯茎叶生长,增强单株光合势,同时,植株茎叶钾素质量分数增大,渗透调节能力增强,从而提高甘薯的抗旱性;施钾增大干物质向块根的分配,提高块根产量,而且干旱胁迫下甘薯的适宜施钾量低于正常灌水。