α-酮戊二酸对氨氮胁迫下草鱼鳃Na+/K+-ATP酶活性及血液生化指标的影响

试验旨在研究饲粮添加α-酮戊二酸(α-ketoglutarate, α-KG)对氨氮胁迫下草鱼(Ctenopharyngodon idellus)鳃Na+/K+-ATP酶活性及血液生化指标的影响。选取初始体重为(24.79±0.11) g的健康草鱼, 随机分为3个处理组(对照组, 养于曝气后氨氮浓度为1.51 mg/L的自来水中并饲喂基础饲粮; 氨氮组, 养于氨氮浓度为18.37 mg/L的水中并饲喂基础饲粮; α-KG组, 养于氨氮浓度为18.37 mg/L的水中并饲喂添加0.75% α-KG的饲粮)。每处理组设3个重复, 每个重复30尾鱼, 养殖试验为期42d, 分别于第1、第14、第28和第42天采样。结果表明:在饲料中添加α-KG能够有效缓解氨氮胁迫导致的草鱼血浆氨含量(1d)、谷草转氨酶(Aspartate transaminase, AST)活性(14d)、碱性磷酸酶(Alkaline phosphatase, ALP)活性(28d)的显著升高和鳃Na+/K+-ATP酶活性(28d)、血浆谷丙转氨酶(Alanine aminotransaminase, ALT)(28d和42d)活性、血浆尿素(UREA)含量(28d)的显著降低, 显著增加氨氮胁迫下草鱼血浆球蛋白(Globulin, GLB)含量(28d)。即饲粮α-KG的适量添加能够有效缓解草鱼氨氮胁迫所致的血氨含量升高, 维持氨氮胁迫下草鱼鳃Na+/K+-ATP酶、血浆谷丙转氨酶、谷草转氨酶、碱性磷酸酶的活性和血浆球蛋白、尿素含量的稳定, 从而有利于草鱼缓解氨氮胁迫。     

配合饲料和鲢鱼肉对大鲵生长的比较试验

为探讨人工配合饲料和鲢鱼肉对大鲵生长、消化和抗氧化能力的影响,试验选取初始体重为(20.99±0.15) g的大鲵幼体48尾,随机分成2组,每组3个重复,每个重复8尾,分别投喂人工配合饲料(粗蛋白55.67%,粗脂肪6.83%)和鲢鱼肉(粗蛋白18.03%,粗脂肪4.11%)共92d。结果显示:(1)饲料组大鲵的增重率(WGR)、特定生长率(SGR)、蛋白质沉积率(PRR)和肌肉蛋白质合成能力均显著高于鱼肉组,饲料系数(FCR)和存活率(SR)在两个试验组之间无显著差异(P>0.05)。(2)在大鲵摄食人工配合饲料后,全鲵粗蛋白、皮肤胶原蛋白及粗灰分含量均显著高于鱼肉组(P<0.05),而全鲵水分、粗脂肪与肌肉的粗脂肪和粗灰分含量显著低于鱼肉组(P<0.05)。(3)饲喂鲢鱼肉的大鲵胃蛋白酶活性显著高于饲料组(P<0.05),而两个试验组的胃H⁺-K⁺-ATP酶和肠道消化酶活性均无显著差异(P>0.05)。(4)饲喂人工配合饲料的大鲵肝脏总抗氧化能力(TAOC)和超氧化物歧化酶(SOD)活性显著高于鱼肉组(P&l...     

饲料中添加磷虾水解物对大菱鲆幼鱼生长性能、体组成及相关酶活性的影响

选取初始体重为(9.46±0.01) g的大菱鲆(Scophthalmus maximus L.)为研究对象, 以30%鱼粉组为对照, 分别添加5%磷虾水解物(LKH)和10%磷虾水解物(HKH)以替代鱼粉蛋白, 配制3组等氮等脂的饲料, 在室内流水养殖系统进行为期10周的养殖实验, 旨在探究饲料中添加磷虾水解物对大菱鲆幼鱼生长性能、体组成及相关酶活性的影响。结果显示, HKH组大菱鲆幼鱼的特定生长率(SGR)、饲料效率(FE)、蛋白质效率比(PER)、蛋白质沉积率(PPV)均显著高于对照组(P<0.05), 但摄食率(FI)显著低于对照组(P<0.05); LKH、HKH组大菱鲆幼鱼肌肉总氨基酸含量和必需氨基酸含量显著高于对照组(P<0.05); LKH、HKH组肝脏谷草转氨酶(GOT)活性显著高于对照组(P<0.05), 而血清GOT活性与对照组无显著性差异(P>0.05); HKH组肝脏谷丙转氨酶(GPT)活性显著高于对照组和LKH组(P<0.05), 但血清GPT活性显著低于LKH组和对照组(P<0.05); HKH组肠道淀粉酶活性显著高于对照组(P<0.05), 同时随着磷虾水解物添加量的升高, 肠道及幽门盲囊胰蛋白酶活性先降低后升高, 且在HKH组显著高于对照组(P<0.05)。综上结果表明, 在饲料中添加10%磷虾水解物能够提高大菱鲆幼鱼的生长性能, 促进其氨基酸代谢和消化吸收。     

山药多糖对老年性痴呆小鼠抗氧化能力的影响

目的:探讨山药多糖对老年性痴呆小鼠抗氧化能力的影响。方法:采用三氯化铝复制痴呆小鼠模型,将50只昆明种小鼠随机分5组(n=10):对照组、模型组和山药多糖低、中、高剂量组,山药多糖剂量分别为100 mg/kg·d、300 mg/kg·d、500 mg/kg·d。治疗组用不同剂量山药多糖分别灌胃90 d。测定小鼠脑系数、脑组织丙二醛(MDA)含量、Na+-K+-ATP酶和Mg2+-ATP酶活性,以及血清氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性。结果:山药多糖能显著提高痴呆模型小鼠脑系数、Na+-K+-ATP酶和Mg2+-ATP酶活性、以及SOD和CAT活力;显著降低MDA含量。结论:增强脑组织ATP酶活性和提高机体抗氧化能力可能是山药多糖防治老年性痴呆的作用机制之一。     

大豆皂甙对杂交黄颡鱼生长、免疫及肠道健康的影响

为探究大豆皂甙对杂交黄颡鱼(Pelteobagrus fulvidraco♀×Pelteobagrus vachelli♂)生长、免疫及肠道健康的影响,在鱼粉、虾粉及玉米浓缩蛋白为蛋白源的基础饲料中分别添加0、0.20%、0.40%、0.80%、1.60%和4.00%的大豆皂甙,配制成6种等氮等脂的饲料饲喂初始质量为(1.0±0.17) g的杂交黄颡鱼,分别记为D0、D0.2、D0.4、D0.8、D1.6和D4.0等处理组,每组设3个重复,每个重复30尾鱼。60d饲养试验结束后测定生长指标、体组成、血清免疫、抗氧化酶活性和肠道炎症因子表达量等变化。结果显示:(1)与D0组相比,添加大豆皂甙的处理组增重率和特定生长率均显著性降低(P<0.05),饲料系数显著性升高(P<0.05)。试验鱼体蛋白含量和肌肉脂肪含量先降低后升高,体脂含量和肌肉蛋白含量先上升后下降。(2)随着饲料皂甙水平的提高,血清T-AOC持续降低, AKP、NO和CAT活性先升高后降低, ACP活性先降低后升高。(3) D0.8、D1.6和D4.0组试验鱼肝脏ACP活性显著高于其他组(P<0.05); D...     

饲料中添加杜仲叶粉对黄河鲤体成分、肌肉氨基酸组成和生理指标的影响

试验以黄河鲤(Cyprinus carpio)为研究对象,以饲料中杜仲(Eucommia ulmoides)叶粉0添加组为对照组,2%、4%、6%和8%添加组为实验组,每组3个平行,对黄河鲤[体重:(505.13±1.37) g]进行55d的投喂试验,旨在探讨杜仲叶粉在黄河鲤饲料中的应用效果。结果表明:(1)黄河鲤背肌脂肪含量随饲料中杜仲叶粉添加量升高显著下降,粗蛋白含量显著上升(P<0.05)。除6%添加组外,鱼体粗灰分、粗蛋白和粗脂肪鲜重含量随杜仲叶粉添加量升高呈上升趋势(P<0.05),鱼体鲜重水分含量呈显著下降趋势(P<0.05);(2)在黄河鲤肌肉中检出16种氨基酸,杜仲叶粉添加显著影响肌肉中苏氨酸、丝氨酸和组氨酸含量(P<0.05)。酸味氨基酸总量与总氨基酸比值在2%添加组显著高于其他处理组,药效氨基酸总量与总氨基酸比值则在2%添加组显著低于其他处理组(P<0.05);(3)黄河鲤血浆和肝脏中GSH-PX、MDA、AKP和ACP活性随饲料中杜仲叶粉添加量增加整体呈先升高后降低趋势,血浆和肝脏中SOD活性呈显著上升趋势(P<0.05)。血浆...     

美洲鳗鲡幼鱼饲料中鱼油的适宜添加水平研究

为研究饲料中鱼油添加水平对美洲鳗鲡(Anguilla rostrata)幼鱼生长性能、消化酶、体成分及肝脏脂肪代谢的影响, 以确定美洲鳗鲡幼鱼饲料中鱼油的适宜添加水平, 选用初始体重(8.34±0.12) g的美洲鳗鲡幼鱼800尾, 随机分成5组, 每组4个重复, 每个重复40尾; 分别投喂添加0(对照组)、3%(FO3组)、6%(FO6组)、9%(FO9组)和12%(FO12组)鱼油的试验饲料, 试验期56d。结果表明, 饲料中添加鱼油显著影响美洲鳗鲡幼鱼生长性能, FO6组美洲鳗鲡幼鱼的增重率、投饵率和饲料效率显著高于其他处理组(P<0.05)。与对照组相比, 鱼油添加组美洲鳗鲡幼鱼肠道脂肪酶活性显著提高(P<0.05), 蛋白酶和淀粉酶活性显著降低(P<0.05); FO6组、FO9组和FO12组全鱼粗脂肪含量显著提高(P<0.05), 全鱼粗蛋白质含量在FO12组显著降低(P<0.05), 全鱼水分和灰分含量无显著变化(P>0.05); FO9组和FO12组脂肪酸合成酶活性显著降低(P<0.05), FO12组脂蛋白酯酶和肝脂酶活性显著升高(P<0.05)。综上, 饲料中添加适宜鱼油水平可以提高美洲鳗鲡幼鱼的生长性能, 调节肠道脂肪酶活性、全鱼粗脂肪含量和肝脏脂肪代谢酶水平或活性; 美洲鳗鲡幼鱼获得最佳增重率和饲料效率时, 饲料中鱼油添加水平推荐为6.43%—6.78%。     

低蛋白饲料补充必需氨基酸对异育银鲫生长、氨基酸转运和mTOR信号通路相关基因的影响

实验以初重为(12.71±0.11) g的异育银鲫“中科5号”(Carassius gibelio var.CAS V)为研究对象,基于异育银鲫必需氨基酸需求量,探究在低蛋白饲料中补充必需氨基酸对异育银鲫生长、消化、氨基酸转运和mTOR信号通路相关基因表达的影响。实验设计3组等能饲料:CON组(35%粗蛋白)、LP组(28%粗蛋白)和LP+EAA组(28%粗蛋白+晶体氨基酸),养殖周期为50d。实验结果显示:低蛋白饲料中补充必需氨基酸显著提高异育银鲫生长性能(P<0.05),并与CON组无显著差异(P>0.05);LP+EAA组的肝脏谷草转氨酶活性显著高于LP组(P<0.05),而谷丙转氨酶活性各组间无显著差异(P>0.05);补充必需氨基酸对肠道中胰蛋白酶和淀粉酶活性有显著影响(P<0.05),而对糜蛋白酶和脂肪酶无显著影响(P>0.05)。肠道中cat2、asct2和b⁰at1三种氨基酸转运蛋白显著上调(P<0.05),LP组的b^0,+at的相对表达量显著下调(P<0.05),而pept1的...     

不同投喂频率下复合非粮蛋白源替代鱼粉饲料对大口黑鲈生长性能和健康的影响

为探究投喂频率对不同水平的复合非粮蛋白源替代饲料鱼粉对大口黑鲈(Micropterus salmoides)生长性能、血浆生化、肠道形态和抗氧化的影响,设计了棉籽浓缩蛋白、乙醇梭菌蛋白、黄粉虫粉和小球藻4种非粮蛋白源混合(8:5:3:4)后替代0、30%、60%和90%的鱼粉的四种等氮等脂饲料(D1、D2、D3和D4),设置3个投喂频率(1、2和4次/d)。每个处理组3个重复,每个重复50尾体重为(14.23±0.07) g的大口黑鲈幼鱼,进行为期8周的室外养殖实验。结果显示,在不同投喂频率条件下,摄食D4饲料组大口黑鲈的特定生长率(SGR)和蛋白质沉积率(PRE)显著低于D1—D3组,饲料系数(FCR)显著升高(P<0.05)。在各饲料组中,投喂1次/d组的特定生长率显著低于2和4次/d投喂组(P<0.05)。在不同投喂频率条件下,摄食D4饲料组大口黑鲈血浆胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)含量显著低于D1组,谷丙转氨酶(ALT)活性显著高于D1组(P<0.05)。在各饲料组中,投喂1次/d大口黑鲈血浆葡萄糖(Glu)含量,碱性磷酸酶(AKP)和谷草转...     

发酵饲料对日本沼虾生长性能、抗氧化能力及肠道微生物的影响

为探究发酵饲料在日本沼虾中的养殖效果,设计5个试验组,分别投喂L1(100%基础饲料组)、L2(87.5%基础饲料+12.5%发酵饲料)、L3(75%基础饲料+25%发酵饲料)、L4(50%基础饲料+50%发酵饲料)和L5(100%发酵饲料)。试验选取大小相近的日本沼虾(0.09±0.01) g进行为期56d的养殖试验,评估日本沼虾生长性能,抗氧化指标和肠道微生物组成。结果显示,饲料经过发酵后可溶蛋白和小肽含量得到显著提高(P<0.05),饲料有益菌含量增加,霉菌得到抑制。养殖试验表明各组存活率均在80%以上,增重率呈先上升后下降趋势, L3和L4组增重率显著高于对照组(P<0.05),饵料系数显著低于对照组(P<0.05)。L3、L4和L5组超氧化物歧化酶(SOD)活性显著高于L1组(P<0.05), L2、L3和L4组丙二醛(MDA)含量显著低于L1组(P<0.05),L2和L5超氧阴离子清除率显著高于L1组(P<0.05)。各试验组血清谷丙转氨酶(ALT)和谷草转氨酶(AST)含量均显著低于对照组(P<0.05)。肠道微生物测序结果显示,...     

日粮中添加桑叶提取物和1-脱氧野尻霉素对大鲵生长、消化、免疫能力和肠道菌群的影响

为探究桑叶物提取物(MLE)和单体1-脱氧野尻霉素(DNJ)对大鲵(Andrias davidianus)生长、消化、免疫能力和肠道菌群影响的差异,研究以基础饲料为对照组,分别添加0.75%的MLE和0.04‰的DNJ制成3种等氮等脂的饲料,饲喂初始均重为(47.81±0.23) g的大鲵90d。结果:MLE组和DNJ组增重率和饲料效率显著提高(P<0.05);肠道脂肪酶和胰蛋白酶活力显著提高(P<0.05),肠道丙二醛、血浆内毒素显著降低(P<0.05),肠黏膜绒毛数量显著增加(P<0.05),肠黏膜上皮细胞间紧密连接更加紧密;与对照组相比, MLE组雷帕霉素靶蛋白(Target of rapamycin, TOR)、白细胞介素-10 (Interleukin, IL-10)、多聚免疫球蛋白受体(Polymeric immunoglobulin receptor, pIgR)、类Toll受体2(Toll-like receptor 2, TLR2)和髓样分化初级反应基因88 (Myeloid differentiation primary response g...     

Relationships between membrane lipids and ion transport in red blood cells of Dahl rats

Distinct changes of membrane lipid content could contribute to the abnormalities of ion transport that take part in the development of salt hypertension in Dahl rats. The relationships between lipid content and particular ion transport systems were studied in red blood cells (RBC) of Dahl rats kept on low- and high-salt diets for 5 weeks since weaning. Dahl salt-sensitive (SS/Jr) rats on high-salt diet had increased blood pressure, levels of plasma triacylglycerols and total plasma cholesterol compared to salt-resistant (SR/Jr) rats. Furthermore, RBC of SS/Jr rats differed from SR/Jr ones by increased content of total membrane phospholipids, but membrane cholesterol was not changed significantly. SS/Jr rats had higher RBC intracellular Na+ (Na(i)+) content and enhanced bumetanide-sensitive Rb+ uptake. RBC membrane content of cholesterol and phospholipids correlated positively with RBC Na(i)+ content, with the activity of Na+-K+ pump and Na+-K+-2Cl- cotransport and also with Rb+ leak. The content of phosphatidylserines plus phosphatidylinositols was positively associated with RBC Na(i)+ content, with the activity of Na+-K+ pump and Na+-K+-2Cl- cotransport and with Rb+ leak. The content of sphingomyelins was positively related to Na+-K+-2Cl- cotransport activity and negatively to ouabain-sensitive Rb+-K+ exchange. We can conclude that observed relationships between ion transport and the membrane content of cholesterol and/or sphingomyelins, which are known to regulate membrane fluidity, might participate in the pathogenesis of salt hypertension in Dahl rats.     

Gill Na+-K+-ATPase activity correlates with basolateral membrane lipid composition in seawater- but not freshwater-acclimated Arctic char (Salvelinus alpinus)

The successful migration of euryhaline teleost fish from freshwater to seawater requires the upregulation of gill Na+-K+-ATPase, an ion transport enzyme located in the basolateral membrane (BLM) of gill chloride cells. Following 39 days of seawater exposure, Arctic char had similar plasma sodium and chloride levels as individuals maintained in freshwater, indicating they had successfully acclimated to seawater. This acclimation was associated with an eightfold increase in gill Na+-K+-ATPase activity but only a threefold increase in gill Na+-K+-ATPase protein number, suggesting that other mechanisms may also modulate gill Na+-K+-ATPase activity. We therefore investigated the influence of membrane composition on Na+-K+-ATPase activity by examining the phospholipid, fatty acid, and cholesterol composition of the gill BLM from freshwater- and seawater-acclimated Arctic char. Mean gill BLM cholesterol content was significantly lower ( approximately 22%) in seawater-acclimated char. Gill Na+-K+-ATPase activity in individual seawater Arctic char was negatively correlated with BLM cholesterol content and positively correlated with %phosphatidylethanolamine and overall %18:2n6 (linoleic acid) content of the BLM, suggesting gill Na+-K+-ATPase activity of seawater-acclimated char may be modulated by the lipid composition of the BLM and may be especially sensitive to those parameters known to influence membrane fluidity. Na+-K+-ATPase activity of individual freshwater Arctic char was not correlated to any membrane lipid parameter measured, suggesting that different lipid-protein interactions may exist for char living in each environment.     

Suppression of hepatic fatty acid synthase by feeding alpha-linolenic acid rich perilla oil lowers plasma triacylglycerol level in rats

This study was performed to determine the effects of dietary perilla oil, a n-3 alpha-linolenic acid (ALA) source, on hepatic lipogenesis as a possible mechanism of lowering triacylglycerol (TG) levels. Male Sprague-Dawley rats were trained for a 3-hour feeding protocol and fed one of five semipurified diets as follows: 1% (w/w) corn oil control diet, or one of four diets supplemented with 10% each of beef tallow, corn oil, perilla oil, and fish oil. Two separate experiments were performed to compare the effects of feeding periods, 4 weeks and 4 days. Hepatic and plasma TG levels were decreased in rats fed perilla oil and fish oil diets, compared with corn oil and beef tallow diets. The activities of hepatic lipogenic enzymes such as fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase, and malic enzyme were suppressed in the fish oil, perilla oil, and corn oil-fed groups, and the effect was the most significant in the fish oil-fed group. Also, the activities of glycolytic enzymes, glucokinase, and L-pyruvate kinase showed the similar trend as that of lipogenic enzymes. The activity of FAS, the key regulatory enzyme in lipogenesis, was positively correlated with hepatic and plasma TG levels and reduced significantly in the perilla oil-fed group compared with corn oil-fed group. In addition, the FAS activity was negatively correlated with the hepatic microsomal content of EPA and DHA. In conclusion, suppression of FAS plays a significant role in the hypolipidemic effects observed in rats fed ALA rich perilla oil and these effects were associated with the increase of hepatic microsomal EPA and DHA contents.     

甘草对大鲵抗嗜水气单胞菌感染的作用

通过投喂甘草提取物, 研究了甘草对大鲵(Andrias davidianus)抗嗜水气单胞菌(Aeromonas hydrophila)感染的作用。连续投喂56d, 从28d开始, 药物组血清溶菌酶活性先升后降, 呈抛物线趋势, 低剂量组在42d出现最大值(158.4±34.7) U/mL, 高剂量组在35d出现最大值(178.3±28.8) U/mL, 两者都显著高于同期对照组(P<0.05)。药物组在最后两次采样期, 即42d和56d时, 肾脏巨噬细胞吞噬活性显著高于对照组(P<0.05)。低剂量组和高剂量组最大值均出现在42d, 分别为(59.4±8.5)%和(58.4±5.2)%。同期相比, 药物组白细胞比容值均高于对照组。其中, 高剂量组在28d时白细胞比容值为(5.8±1.7)%, 低剂量组在56d时为(5.5±0.8)%, 高剂量组在56d时为(5.9±1.7)%, 三者都显著高于同期对照组(P<0.05)。药物组和对照组的脾脏脏器系数之间没有显示出显著差异。最后一次采样(56d)后人工感染嗜水气单胞菌, 对照组死亡率为90%, 低剂量组和高剂量组都为60%, 均低于对照组, 而药物组免疫保护率为33.3%, 也都高于对照组。结果表明, 投喂甘草提取物可在一定程度上提高大鲵对嗜水气单胞菌的抗性。     

Major biological activities of the skin secretion of the Chinese giant salamander, Andrias davidianus

Amphibian skin can produce abundant secretion which contains many bioactive compounds. In this work, skin secretion of the Chinese giant salamander (Andrias davidianus) was obtained by mild electrical stimulation of the dorsal skin surface, and the main physiopathological properties of the secretion were described. Intraperitoneal administration of the skin secretion caused lethal effects in mice. Low doses of the skin secretion induced significant systemic and local effects like edema and nociception in mice. The activities of phospholipase A2 and proteolytic enzyme were likely related to the physiopathological activities observed. The work proved the complex toxic effects of the Chinese giant salamander skin secretion and provided clues to study its physiological function further.     

中国大鲵研究概况

中国大鲵(Andrias davidianus)为我国特有物种,也是国家二类保护水生野生动物.野生大鲵多栖息在山区溪流里,喜穴居,怕光怕声,以鱼蟹等水生动物为食,从数量上看,以陕西秦岭山区居多.大鲵经济价值极高,在美食、保健、医药、观赏等方面均具有广泛开发利用的前景,因而颇受社会各界关注.近年来对大鲵的科学研究涉及多个...     

Effect of the dietary alpha-linolenate/linoleate balance on leukotriene production and histamine release in rats

Rats were fed semi-purified diets supplemented either with safflower seed oil rich in linoleate (18:2n-6) or with perilla seed oil rich in alpha-linolenate (18:3n-3) through two generations. In the major phospholipids of polymorphonuclear leukocytes (PMNs), the proportions of n-6 polyunsaturated fatty acids (18:2, 20:4, 22:4 and 22:5) were higher but those of n-3 acids (20:5, 22:5 and 22:6) were lower in the safflower group than in the perilla group. When stimulated with a calcium ionophore, the PMNs from the safflower group produced 27% more leukotriene (LT)B4 than those from the perilla group. The formation of LTB5 which has biological activities less than 1/10 those of LTB4, was negligible in the safflower group but was 40 ng/10(7) PMN cells in the perilla group. The amount of the total LTB formed in the perilla group tended to be more than in the safflower group. The formation of SRS-A (slow-reacting substances of anaphylaxis) by PMNs was determined by measuring the spasmogenic activities of LTs on guinea pig ileum. SRS-A activity was 59% higher in the safflower group than in the perilla group. In contrast, histamine release from rat peritoneal mast cells was not significantly different between the two groups. Thus, the increasing the alpha-linolenate/linoleate ratio of diets results in the decreased formation of LTs derived from 20:4n-6 in PMNs. This may be beneficial in lowering the severity of allergic and inflammatory responses caused by LTs, and thereby shifting the pathological symptoms to normal self-defense mechanism.     

Stimulation of sodium-calcium exchange by cholesterol incorporation into isolated cardiac sarcolemmal vesicles

Modification of the cholesterol content of highly purified cardiac sarcolemma from dog ventricles was accomplished by incubation with phosphatidylcholine liposomes containing various amounts of cholesterol. The degree of cholesterol enrichment could be varied by changing the liposomal cholesterol/phospholipid ratio or varying the liposome-membrane incubation time. Na+-Ca2+ exchange measured in cholesterol-enriched sarcolemmal vesicles was increased up to 48% over control values. The stimulation of Na+-Ca2+ exchange was associated with an increased affinity of the exchanger for Ca2+ (Km = 17 microM compared with Km = 22 microM for control preparations). Na+-Ca2+ exchange measured in cholesterol-depleted membrane preparations was decreased by 15%. This depressed activity was associated with a decreased affinity of the exchanger for Ca2+ (Km = 27 microM). These changes were not due to either a change in membrane permeability to Ca2+ or an increase in the amount of Ca2+ bound to sarcolemmal vesicles. The stimulating effect of cholesterol enrichment was specific to the Na+-Ca2+ exchange process since sarcolemmal Ca2+-Mg2+ ATPase activity was depressed 40% by cholesterol enrichment. Further, K+-p-nitrophenylphosphatase and Na+-K+ ATPase activities were depressed in both cholesterol-depleted and cholesterol-enriched sarcolemmal vesicles. In situ oxidation of membrane cholesterol completely eliminated Na+-Ca2+ exchange. These results suggest that cholesterol is intimately associated with Na+-Ca2+ exchange and may interact with the exchange protein and modulate its activity.