NEW METHOD TO MEASURE THE CAPILLARY PERMEABILITY SURFACE AREA PRODUCT (PS) IN RABBIT SKELETAL MUSCLE UNDER VITAL MICROSCOPIC OBSERVATION.

To study the transcapillary exchange of water-soluble substances, the authors tried a new method to measure the capillary permeability surface area product (PS) under a vital microscopic field. As a blue dye indicator, Cr-EDTA (MW:341, maximum light absorption at 542nm) was solved in the suffusate of a Tyrode solution (20g/dl) and stained the rabbit tenuissimus muscle for about 30 min. After changing it to a Cr-EDTA free solution, the rate of the indicator washout from tissue to capillary was recorded with a photocell placed on a VTR monitor connected to the microscope. The time constant of the clearance curve gave the reciprocal of the PS value. By this method the PS values reflect the local variations in the substance exchange rate might be obtained. The fundamental nature of the clearance curve was studied, including the effect of the local capillary flow.