Renal Effects of Multiple Infusion of Pyridoxalated‐Hemoglobin‐Polyoxyethylene Conjugate (PHP) Solution in Dogs

Abstract

Pyridoxalated‐hemoglobin‐polyoxyethylene conjugate (PHP), which is made from out‐dated human red blood cells by two major chemical modifications, namely pyridoxalation and conjugation with polyoxyethylene (POE), is currently under development as a physiological oxygen carrier. This study assessed the effects of PHP‐88 solution, which contains 8% (wt/vol) each of hemoglobin (Hb) and maltose, on renal function when it was infused 3 times every other day into the intact circulation of 8 dogs (5 dogs for the PHP group and 3 for the control group; 20 ml/kg for the first infusion, and 10 ml/kg each for the second and third infusions, at the rate of 2.5 ml/h/kg). Serial determinations of glomerular filtration rate (GFR) and renal plasma flow (RPF) were carried out pre‐ and postinfusion for up to 3 months along with measurements of blood and urine analyses, urine output rate, fractional excretion of sodium (FES), and free water clearance (CH2O). The results showed that plasma colloid osmotic pressure (COP) elevated an average of 3.3 mm Hg (p = 0.0085), and GFR and RPF tended to increase by 13% (NS) and 38% (NS), respectively, immediately after the third infusion with PHP solution. Urine output rate increased during and after the infusion, and FES and CH2O also increased for 24 h after the infusion in both groups. Blood urea nitrogen, serum creatinine, and serum Na+ concentrations were not affected greatly by the infusions, but hematocrit was decreased by 8% in the PHP group, indicating approximately a 42% expansion of plasma volume. These changes were observed to return to their preinfusion levels by 1 week postinfusion. Renal histology of the PHP group obtained at 2 weeks postinfusion revealed vacuole formation in the proximal tubules which was not associated with any pathologic changes indicative of cell death or regeneration. In 4 out of 5 dogs at 3 months postinfusion (necropsy), the vacuoles were not present. Though urinary N‐acetyl β‐glucosaminidase (NAG) activity had significantly increased after infusion, it returned to the preinfusion level by 1 month postinfusion. No detrimental effect of vacuoles on the assessed renal tubular functions was confirmed in the present study. The result demonstrated that multiple infusions of PHP solutions were well tolerated in normal dogs, and the observed effects were conceived predominantly attributable to the physiological response of the kidneys to an oncotic load into the circulation, which produced plasma volume expansion.

The Impact of Polyethylene Glycol Conjugation on Bovine Hemoglobin's Circulatory Half‐Life and Renal Effects in a Rabbit Top‐Loaded Transfusion Model

“…Similar effects have been noted following the modification of other compounds with PEG (26). In contrast, non-PEG modified hemoglobin compounds have been shown to induce the development of macroscopic hemoglobinuria when examined in low volume top-loading and exchange transfusion models (6,10, [27][28][29][30].…”

“…The large volume expansion (40% overload) given within a short period of time may be responsible for the development of extravasation. Formulation buffer, which lacks proteins and subsequently has few plasma volume expansion capabilities (10, 30,38), did not affect renal morphology. Rabbit models of a 30% isovolumetric exchange transfusion of PEG-Hb, (unpublished data) or rat studies with a 25 ml/kg overload of PEG-Hb did not demonstrate the development of red cell extravasation (39,40) indicating that the volume overload may have been responsible.…”

“…In terms of hemoglobin solutions, a correlation between hemoglobin dosage and vacuole formation has been exhibited by dose-dependent vesicle production in the dog (28). The transitory nature of vacuole accumulation after hemoglobin infusion has been observed and supported by others (10, [28][29][30]33). The transient increase in vacuole formation has not been shown to adversely affect either the tubular function or lysosomal protein metabolism of tubule cells (47,48).…”