CHEMICAL, CLINICAL, AND IMMUNOLOGICAL STUDIES ON THE PRODUCTS OF HUMAN PLASMA FRACTIONATION. XXXIV. COMPARATIVE STUDIES ON THE NUTRITIVE VALUE OF ORALLY AND INTRAVENOUSLY ADMINISTERED HUMAN SERUM ALBUMIN IN MAN 123

Abstract

Normal human serum albumin was administered orally or intraven. to 5 normal individuals as a sole source of N for 7 to 16 days. N balance and plasma protein concn. were studied and the results compared with those obtained with intravenous casein hydrolysate, oral lactalbumin, and oral human albumin. Albumin administered orally in 50 g. daily amts. maintained wt. and N balance, even though it was not supplemented with tryptophane or isoleucine. Albumin administered intraven. in 37.5 g. daily amts. maintained a positive N balance and produced a selective rise in plasma albumin concn. When the albumin was administered intraven. in 75 g. daily amts. it produced a markedly positive N balance with minimum N excretion, in contrast with a N excretion which approached the intake both in a previous period, in which casein hydrolysate was provided intravenously, and in an after period, in which albumin was administered orally. After the intraven. injns. of albumin were discontinued in 2 subjects, 50% of the albumin retained in the plasma disappeared in 4 to 6 days, and in 3 wks. the level had fallen to nearly its original value. It is suggested that intraven. administered albumin in normal individuals diffuses first into the lymphatics where an equilibrium is established. It then slowly undergoes metabolism being broken down gradually, and probably completely, into its constituent amino acids; these are either deaminated, and their N excreted, or are resynthesized into new tissue protein.