MICRO-INJECTION STUDIES OF CAPILLARY PERMEABILITY

Abstract

Effects upon capillary permeability of O lack, of high tensions of CO2, and of decreased pH value were studied in single capillaries of the frog mesentery, by direct measurement of fluid movement in cu. micra per sq. u of capillary wall per sec, with measurement of capillary pressure. Immediately after a 3 min. period of O lack, fluid filtered through the capillary wall at approximately 4 times the normal rate. Increased permeability of the wall permitted also passage of protein, thus reducing effective osmotic pressure of plasma proteins to almost 1/2 normal. Movement of fluid through the asphyxiated capillary wall was directly proportional to the difference between capillary pressure and the effective osmotic pressure of the plasma proteins, indicating that the wall still acted merely as a passive filter, though more permeable than normal. With return of circulation the capillary wall rapidly recovered its impermeability to protein, and rate of fluid movement was also reduced practically to normal. Exposure of the mesentery to Ringer''s fluid half saturated with CO2 produced no change in fluid movement. Complete saturation increased rate of fluid movement very slightly, but the wall remained normally impermeable to protein. Decrease in pn produced almost no change in fluid movement within physiological limits, though at pn 4.0 the characteristic effects of injury appeared.