ABSTRACT
To evaluate the large pore radius of the glomerular capillary filter, plasma-to-urine fractional clearances of a number of endogenous proteins were assessed in normal and in nephrotic Wistar rats in which proximal tubular reabsorption had been inhibited using lysine. The proteins studied varied in radius from 16.2 A (Beta 2-microglobulin) to 90 A (alpha 2-macroglobulin). The nephrotic syndrome was induced by puromycin aminonucleoside (PAN). A marked restriction of the transport of large proteins across the glomerular capillary wall was found, indicating that there are no non-discriminatory 'shunt pathways' in the glomerular barrier. Rather, there seems to be large pores of radius 110 to 115 A accounting for the clearance of large proteins into the primary urine. This protein excretion pattern was almost the same for control and nephrotic rats, except that in the latter, the number of large pores was increased 170 times. The ratio between the number of large and small pores was calculated to be approximately equal to 7 x 10(-7) in normal rats and to 1.2 x 10(-4) in PAN nephrotic rats, assuming no classic shunt pathways. If classic shunt pathways had still existed, they would normally contribute to no more than approximately equal to 10(-5) of the total glomerular filtration rate. We postulate that very large macromolecules like IgM will not pass the glomerular filter at all under normal conditions, whereas the urine concentration of alpha2-macroglobulin will normally be extremely low.
Subject(s)
Kidney Glomerulus/metabolism , Proteins/metabolism , Animals , Biological Transport, Active , Blood Proteins/metabolism , Capillaries/metabolism , Female , Glomerular Filtration Rate , Immunoglobulin M/metabolism , Kidney Glomerulus/blood supply , Kidney Glomerulus/drug effects , Molecular Weight , Nephrotic Syndrome/chemically induced , Nephrotic Syndrome/metabolism , Proteins/chemistry , Proteinuria/metabolism , Puromycin Aminonucleoside/toxicity , Rats , Rats, Wistar , alpha-Macroglobulins/metabolismABSTRACT
Thermography, clinical examination and 99Tcm-plasmin test were performed in 112 patients and compared with phlebography. The study population consists of consecutive outpatients with symptoms compatible with deep venous thrombosis, who presented during regular clinic hours. Scoring systems were constructed for the clinical and thermographic evaluation. Both thermography and clinical diagnosis were insufficiently sensitive and specific for screening purposes. Plasmin test had a high sensitivity, 95%, but a low specificity. It is possible that a combination of thermography and clinical diagnostic criteria can provide an acceptable screening procedure. Combining thermography with a routine examination by the physician on duty yielded less favourable results.
