Filtration Coefficient of the Capillaries of the Brain

¹ From the Biophysics Division, Department of Physiology, Ohio State University, Columbus, Ohio

The Monro-Kellie doctrine was used as the basis for determination of the filtration coefficient of the capillaries of the cat's brain. An average value of 10.3 x 10^–8 ml/sec/cm H₂O/cm² was found. A linear relation was observed between filtration rate and filtration pressure. The fact that the filtration coefficient of brain capillaries is somewhat higher than that of muscle capillaries suggests that lipoid insoluble molecules actually penetrate the brain capillary membranes readily, but are pumped back by a secretory process.