Renal handling of pseudo-crosslinked hemoglobin

Stabilization of the Hb tetramer has been achieved by the introduction of electrostatic and hydrophobic interactions between the B chains. These Hbs are referred to as pseudo-crosslinked (p-XLHb). To determine if human, bovine or porcine p-XLHbs are excreted by or have adverse effects on renal function, we have determined their plasma retention, renal excretion and effects on glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and Na and K excretion in anesthetized rats. Plasma and urine samples were obtained prior to and after i.v. doses of 20-25 mg·100 gm of p-XLHb or albumin (as a control). Excretion data indicate that a variable portion (6 to 40%) of p-XLHbs appeared in the urine. Regression analysis of the plasma retention curve occasionally indicated two phases; an early fast and later slow phase with T _1/2 s of 25 and 150 min, respectively. The early phase coincided with the presence of p-XLHb in the urine. Small increases in GFR and ERPF, lasting 40 min, occurred immediately after both p-XLHbs or albumin. These functions returned to and were maintained at control values for up to 2 hrs. Larger transient increases in urine flow and in Na and K excretion were also observed. It is concluded that p-XLHb preparations do not appear to have immediate adverse effects on measured renal functional parameters. p-XLHbs appear in the glomerulus as two species; one passes readily and the second is restricted. These findings indicate the importance of measuring renal excretion as well as plasma retention behavior, as the presence of multiple species is more easily evidenced by urinary excretion than by the plasma retention curve. In fact, the preparations used in this study appeared to be stable tetramers in a sedimentation velocity analysis.