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血清白蛋白检测 serum albumin detection
Serum albumin, often referred to simply as albumin, is the most abundant plasma protein in humans and other mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. It also acts as a plasma carrier by non-specifically binding several hydrophobic steroid hormones and as a transport protein for hemin and fatty acids.
Types
The human version is human serum albumin.
Bovine serum albumin, or BSA, is commonly used in immunodiagnostic procedures, clinical chemistry reagents, cell culture media, protein chemistry research and molecular biology laboratories (usually to leverage its non-specific protein binding properties).
[edit] General characteristics
Albumin (when ionized in water at pH 7.4, as found in the body) is negatively charged. The glomerular basement membrane is also negatively charged in the body; some studies suggest that this prevents the filtration of albumin in the urine. According to this theory, that charge plays a major role in the selective exclusion of albumin from the glomerular filtrate. A defect in this property results in nephrotic syndrome leading to albumin loss in the urine. Nephrotic syndrome patients are sometimes given albumin to replace the lost albumin.
Because smaller animals (for example rats) function at a lower blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.
Serum albumin contains eleven distinct binding domains for hydrophobic compounds. One hemin and six long-chain fatty acids can bind to serum albumin at the same time
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin comprises about half of the blood serum protein. It is soluble and monomeric.
The gene for albumin is located on chromosome 4 and mutations in this gene can result in various anomalous proteins. The human albumin gene is 16,961 nucleotides long from the putative "cap" site to the first poly(A) addition site. It is split into 15 exons which are symmetrically placed within the 3 domains that are thought to have arisen by triplication of a single primordial domain.
Albumin is synthesized in the liver as preproalbumin which has an N-terminal peptide that is removed before the nascent protein is released from the rough endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin.
The reference range for albumin concentrations in blood is 30 to 50 g/L. It has a serum half-life of approximately 20 days. It has a molecular mass of 67 kDa.
Functions of albumin
Maintains oncotic pressure
Transports thyroid hormones
Transports other hormones, particularly fat soluble ones
Transports fatty acids ("free" fatty acids) to the liver
Transports unconjugated bilirubin
Transports many drugs, and serum albumin levels can affect the half-life of drugs.
Competitively binds calcium ions (Ca2+)
Buffers pH
[edit] Pathology
[edit] Hypoalbuminemia
Low blood albumin levels (hypoalbuminemia) can be caused by:
liver disease / Cirrhosis of the liver (most commonly)
Decreased production (as in starvation/malnutrition/malabsorption)
Excess excretion by the kidneys (as in nephrotic syndrome)
Excess loss in bowel (protein losing enteropathy e.g. Menetrier"s)
Burns (Plasma loss in the absence of skin barrier)
Redistribution (hemodilution [as in Pregnancy], increased vascular permeability or decreased lymphatic clearance)
Acute disease states (referred to as a negative acute phase protein)
Mutation causing analbuminemia (very rare)
[edit] Hyperalbuminemia
Typically is a sign of severe dehydration.
[edit] Glycation (Glycosylation) of Serum Albumin
It has been known for a long time that human blood proteins like hemoglobin [1] and serum albumin [2][3] may undergo a slow non-enzymatic glycation, mainly by formation of a Schiff base between ε-amino groups of lysine (and sometimes arginine) residues and glucose molecules in blood (Maillard reaction). This reaction can be inhibited in the presence of antioxidant agents [4]. Although this reaction may happen normally [5] , elevated glycoalbumin is observed in diabetes mellitus [6].
Glycation has the potential to alter the biological structure and function of the serum albumin protein [7][8][9][10]. Moreover, the glycation finally can result in the formation of Advanced Glycosylation End Products (AGE), which result in abnormal biological effects. Accumulation of AGEs leads to tissue damage via alteration of the structures and functions of tissue proteins, stimulation of cellular responses, through receptors specific for AGE-proteins, and via generation of reactive oxygen intermediates. AGEs also react with DNA, thus causing mutations and DNA transposition. Thermal processing of proteins and carbohydrates brings major changes in allergenicity. AGEs are antigenic and represent many of the important neoantigens found in cooked or stored foods [11]. They also interfere with the normal product of nitric oxide in cells [12].
Although there are several lysine and arginine residues in the serum albumin structure, very few of them can take part in the glycation reaction [13][14]. It is not clear exactly why only these residues are glycated in serum albumin [15].
[edit] Testing for albumin loss via the kidneys
In the healthy kidney, albumin"s size and negative electric charge exclude it from excretion in the glomerulus. This is not always the case, as in some diseases including diabetic nephropathy, a major complication of uncontrolled diabetes where proteins can cross the glomerulus. The lost albumin can be detected by a simple urine test.[16] Depending on the amount of albumin lost, a patient may have normal renal function, microalbuminuria, or albuminuria.
[edit] Amino Acid Sequence
The approximate sequence of human serum albumin is:
MKWVTFISLL FLFSSAYSRG VFRRDAHKSE VAHRFKDLGE ENFKALVLIA FAQYLQQCPF EDHVKLVNEV TEFAKTCVAD ESAENCDKSL HTLFGDKLCT VATLRETYGE MADCCAKQEP ERNECFLQHK DDNPNLPRLV RPEVDVMCTA FHDNEETFLK KYLYEIARRH PYFYAPELLF FAKRYKAAFT ECCQAADKAA CLLPKLDELR DEGKASSAKQ RLKCASLQKF GERAFKAWAV ARLSQRFPKA EFAEVSKLVT DLTKVHTECC HGDLLECADD RADLAKYICE NQDSISSKLK ECCEKPLLEK SHCIAEVEND EMPADLPSLA ADFVESKDVC KNYAEAKDVF LGMFLYEYAR RHPDYSVVLL LRLAKTYETT LEKCCAAADP HECYAKVFDE FKPLVEEPQN LIKQNCELFE QLGEYKFQNA LLVRYTKKVP QVSTPTLVEV SRNLGKVGSK CCKHPEAKRM PCAEDYLSVV LNQLCVLHEK TPVSDRVTKC CTESLVNRRP CFSALEVDET YVPKEFNAET FTFHADICTL SEKERQIKKQ TALVELVKHK PKATKEQLKA VMDDFAAFVE KCCKADDKET CFAEEGKKLV AASQAALGL
Where the italicized first 24 amino acids are signal and propeptide portions not observed in the transcribed, translated and transported protein but present in the gene. There are 609 amino acids in this sequence with only 585 amino acids in the final product observed in the blood.
小菜G-
人血白蛋白
1.失血创伤、烧伤引起的休克。
2.脑水肿及损伤引起的颅压升高。
3.肝硬化及肾病引起的水肿或腹水。
4.低蛋白血症的防治。
5.新生儿高胆红素血症。
6.用于心肺分流术、烧伤的辅助治疗、血液透析的辅助治疗和成人呼吸窘迫综合征。
血清白蛋白
是血清总蛋白的一部分，由肝脏合成。肝脏疾患时常常检测血清白蛋白含量来协助诊断，判断预后。但是肝脏的代偿能力很强，所以只有当肝脏损害到一定程度时，又经过一定的疾程后，才能够显示出白蛋白质量的变化。
临床意义：
（1）白蛋白浓度升高常见于严重失水，血浆浓缩所致。尚未发现单纯白蛋白浓度升高的疾病。
（2）白蛋白浓度降低的原因与总蛋白浓度降低的原因相同。急性白蛋白浓度降低主要见于大量出血和严重灼伤。慢性白蛋白浓度降低主要见于肝、肾疾病
南yi-
血清白蛋白测定
一种临床化验检查项目、化验标本为静脉血的血清、参考值为40￣55克／升、增高见于脱水、大面积烧伤、高热、急性大出血、慢性肾上腺皮质功能不全等、减低见于营养不良、消化吸收功能不良、慢性肝病、恶性贫血、糖尿病、甲状腺机能亢进症、严重结核病等。
bcg法是血清白蛋白测定的常规方法：
血清白蛋白、球蛋白及其比值的测定是临床常用的生化检验项目之一。通常是将血清白蛋白与总蛋白同时测定，总蛋白减去白蛋白即为球蛋白的含量，并计算a／g比值，其参考值范围为1．5～2．5／1。肝功能损害严重时白蛋白合成减少，肾脏疾病患者白蛋白丢失过多时，均可见a／g比值改变，当a／g<1时，称为a/g比例倒置。