ISSN:1660-8151    

DOI:10.1159/000180362

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:1660-8151    

DOI:10.1159/000180363

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:1660-8151    

DOI:10.1159/000180364

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:1660-8151    

DOI:10.1159/000180365

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The ultrastructural basis of glomerular permeability to protein molecules is reviewed. These studies have relied either on the intrinsic electron density of intravenously injected tracer molecules, or on the peroxidatic activity of a number of peroxidatic enzymes of varying molecular weight. The nature of the final filtration barrier in the glomerulus remains conjectural but two possibilities have been suggested: the glomerular basement membrane (a) is the sole filter and retards the passage of protein molecules in a fashion analogous to gel filtration, or (b) it acts as a coarse filter in series with a fine, filter located in the slit-pore complex. Correlative studies of mathematical models and physiological data tend to favor the latter possibility.

ISSN:1660-8151    

DOI:10.1159/000180366

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Indirect and direct studies indicate that a variety of proteins filtered at the glomerulus are absorbed by the proximal tubule by luminal endocytosis and are hydrolyzed by lysosomal enzymes. Studies on isolated, perfused tubular segments have not demonstrated contraluminal uptake of albumin or insulin. Evidence for transport of intact protein molecules across tubular cells is inconclusive, and additional studies are required to resolve this problem. Experimental findings suggest that the kidney plays an important role in albumin homeostasis. In health, greater than 90% of the small amount of albumin filtered by the glomerulus is absorbed by the proximal tubule and digested therein, which accounts for approximately 10% of total albumin catabolism. Only trace amounts of albumin appear in the urine. In disease, large loads of filtered albumin probably saturate the absorptive-digestive capacity of the proximal tubule and albuminuria ensues. In this circumstance, the kidneys may account for 30–40% of total albumin catabolis

ISSN:1660-8151    

DOI:10.1159/000180367

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The role of the kidney in the metabolism of plasma proteins can be defined by metabolic turnover techniques using representative radioiodinated, purified proteins. Low molecular weight (MW) proteins ( 60,000 M W) are generally retained by the glomerular filter and, therefore, do not normally have a significant exposure to tubular catabolic sites; for this class of proteins the kidney is not normally a primary organ of catabolism. Intermediate and even high M W proteins do pass through an abnormal glomerular filter, and are thereby lost to the body as intact proteins or are taken up and catabolized within tubular cells. In tubular diseases low MW proteins enter the tubular lumen in normal fashion, but are not taken up and catabolized within tubular cells. Thus, their loss pathway changes reciprocably from one of endogenous catabolism to excretion; this is the origin of tubular proteinuria. In nephron-loss disease, both excretion and endogenous catabolism of low MW proteins are diminished. Thus, these proteins accumulate in the blood.

ISSN:1660-8151    

DOI:10.1159/000180368

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The plasma protein concentration is important in the maintenance of plasma volume which, in turn, regulates reabsorption by the renal tubule through the renin-angiotensin aldosterone system and perhaps an additional natriuretic system. In addition, the plasma protein concentration in glomerular capillaries has direct effects on the formation of glomerular filtrate since the oncotic pressure of plasma opposes the hydrostatic pressure for filtration. Similarly, the plasma protein concentration in peritubule capillaries influences the uptake of reabsorbate from the renal tubules. Although there is a large body of evidence indicating a relationship between peritubule protein concentration and sodium reabsorption by the proximal tubule, the mechanisms involved and the importance of peritubule capillary protein concentration in the regulation of proximal sodium reabsorption remain unresolved. Finally, protein plays an important role in the concentrating ability of the kidney.

ISSN:1660-8151    

DOI:10.1159/000180369

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The techniques of differential protein clearance have been used in the study of patients with renal disease in an attempt to predict the nature of the underlying renal abnormality. Many assumptions that underlie their use are subject to doubt, and differential protein clearances appear to predict the nature of the glomerular disease only in patients with nephrotic syndrome and minimal glomerular changes. When the protein clearance is expressed in terms of the glomerular filtration rate (sieving coefficient), it is a useful index to differentiate the proteinurias associated with glomerular or with tubular damage. This physiologic measure can be used as a valid means of expressing protein handling by normal and diseased kidney.

ISSN:1660-8151    

DOI:10.1159/000180370

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Measurement of urinary proteins in proteinuric patients is a complex problem since the concentration, types of protein excreted, and presence of waste products vary considerably. Each method of quantitatíng urinary proteins makes certain assumptions and care must be taken to eliminate artifacts in the determinations. Concentration of urinary proteins without large losses of either all or certain ones must be achieved to quantify specific proteins. Currently, gel filtration and immunochemical methods are most often used for estimation of specific proteins or patterns of all proteins excreted. When combined, these two methods yield fairly rigorous results for the characterization and quantitation of known proteins. This approach has shown that the concept of selectivity of protein excretion does not hold over the protein size spectrum. However, the procedure is time-consuming and therefore is suited only for research studies. A more valid model to sort out the pathophysiologic basis of protein excretion may be a technique for examination of individual proteins or those of specific groups to distinguish between glomerular and tubular proteinuria. A suitable technique for this approach, because of its convenience, is that of protein electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate

ISSN:1660-8151    

DOI:10.1159/000180371

出版商:S. Karger AG    

年代:1974

数据来源: Karger