[Mathematical model of fluid transport in the convoluted portion of the proximal kidney tubules and surrounding capillaries].

Simulating transport of fluid and ions among proximal tubule, interstice and capillaries the mechanism of fluid transport in the kidney was studied. A mathematical model as a system of differential equations was processed with a numerical method by a digital computer. The results showed that 96% of fluid from the proximal convolution into interstice were reabsorbed because of the difference of osmotic pressures caused by HCO3-, ions and 4% -- at the expense of oncotic pressure gradient. Fluid transport from interstice into capillaries is realized by the higher oncotic pressure caused by proteins as a result of previous plasma filtration in the nephron glomerulus.