Respiratory Proteins

The Renal Excretion of Hemoglobin: Regulatory Mechanisms and the Differential Excretion of Free and Protein-Bound Hemoglobin*†

“…The lower estimates of glomerular permeability made in this study are more consistent than previous estimates (9) with the molecular weight and physical characteristics of free hemoglobin (20). However, the question is unanswered as to whether the glomerulus is permeable to the free hemoglobin molecule as such or whether hemoglobin enters glomerular filtrate only after dissociating into smaller parts.…”

“…In view of what is known concerning glomerular permeability and tubular reabsorption of large molecular substances, these heme-protein complexes would be expected to traverse the glomerular membrane with difficulty and would be unlikely to appear in glomerular filtrate in significant concentration under normal circumstances (18,19). The molecular weight and size of methemalbumin is certainly equal to that of al bumin (20), to which the normal glomerulus is believed to be in large measure impermeable (18,19). Although the physical characteristics of protein-bound hemoglobin have not been definitely established, the molecular weight of this hemoglobin-a2 globulin (?)…”

“…The probem raised by Smith (10) as to why the glomerulus is as permeable as it appears to be to (free) hemoglobin, which in molecular weight, at least, is similar to albumin (20), is not resolved. The lower estimates of glomerular permeability made in this study are more consistent than previous estimates (9) with the molecular weight and physical characteristics of free hemoglobin (20).…”

The Distribution of Extracorpuscular Hemoglobin in Circulating Plasma*†

“…a) The electrophoretic characteristics of this moiety were similar to those of protein-bound hemoglobin as described by Smithies and Walker (11,12), Laurell and Nyman (8) and Allison and ap Rees (9), and are those to be expected of hemoglobin which is believed to be bound by a2 globulin (5); b) The demonstration, as described below, of a limiting, maximal concentration of this fraction, with the appearance of another moiety (free hemoglobin) at higher hemoglobin concentrations, is consistent with a protein-binding reaction as has been described for other constituents of plasma (14); c) This fraction is not excreted in the urine (13), an observation consistent with hemoglobin binding by a large-sized plasma protein to which the glomerulus is impermeable; d) The absorption spec-trum of this fraction ( Figure 3) was similar to that of oxyhemoglobin (15), suggesting that the benzidine reacting material which is bound to plasma protein is hemoglobin and not a derivative thereof.…”

The Biosynthesis of Hemoglobin From Iron, Protoporphyrin and Globin*†

“…At tube no. 170, the column was warmed to 250 C. The distortion seen in the hemoglobin S peak was produced by the emergence of some of this hemoglobin before the column warmed to 250 C. the failure to observe an effect with stored globin preparations are consistent with the known instability of purified globin preparations (22) and may explain why other investigators have not observed an effect of globin on heme synthesis (23).…”