SPECTROPHOTOMETRIC MEASUREMENT OF TRACES OF THE DYE T-1824 BY EXTRACTION WITH CELLOPHANE FROM BOTH BLOOD SERUM AND URINE OF NORMAL DOGS

Abstract

A method was devised for extraction and estimation of the blue plasma-vol. dye T-1824 in amts. as small as 0.5 microg. Dye is sorbed on cellophane foils of constant thickness and measured spectrophotometric-ally. Complete recovery (more than 98%) from urine or diluted serum occurs after 24 hrs. at 70 C provided that 1) NaCl is greater than 0.9%; 2) indicated amts. of Aerosol OT are added in order to liberate dye from T-1824 albumin; 3) an excess of cellophane is used. Unit "cellophane value," defined as the product of optical density at 635 millimicrons and wt. in mg. of any foil which is 0.00186 cm. thick, corresponds to 3.0 x 1015 molecules of T-1824. Cellophane value from 0.2 ml. of dye-tinged serum is 1.10 times more than serum optical density in 0.5 cm. cuvette. At various periods in the course of 24 hrs. after intraven. injn. renal clearance of T-1824 was 1.4-2.2 microl./min. and was independent of sex, wt. or urine flow. T-1824 clearance is probably identical to normally occurring albumin clearance because of the great affinity of T-1824 for albumin in the bloodstream.