Functional preservation of the mammalian kidney. I. Normothermia, low-flow perfusion

Effects of four cryoprotectants in combination with two vehicle solutions on cultured vascular endothelial cells

The necessary first step in successful organ cryopreservation will be the maintenance of endothelial cell integrity during perfusion of high concentrations of cryoprotective agents (CPAs). In this report we compare the effects of incubation on cultured porcine endothelial cells at 10 degrees C for 1 h with the CPAs glycerol, dimethyl sulfoxide (Me2SO), ethanediol (EG), and propane-1,2-diol (PG) in the vehicle solutions RPS-2 (high potassium, high glucose) and HP-5NP (low potassium, high sodium), both with and without added colloids. Tritiated adenine uptake and acid phosphatase estimation of cell number were used as indicators of cell viability. HP-5NP was superior to RPS-2 except with Me2SO when the differences in viability were not significant. Adding Haemaccel to HP-5NP improved the results, but adding albumin to RPS-2 was of no significant benefit. Osmotic stress appeared to be the major problem with glycerols use. Beyond 3.0 M the toxicity of Me2SO increased dramatically but it could not be determined if this was osmotic or chemical toxicity. PG was remarkably well tolerated to 3.0 M but a sharp decrease in cell viability beyond this concentration suggests that PG may be most useful with mixtures of other CPAs. Overall, EG appeared to be the least toxic CPA and in the context of vascular preservation warrants further investigation.

Introduction and removal of cryoprotective agents with rabbit kidneys: assessment by transplantation

Rabbit kidneys were perfused with up to 4 M glycerol or propane-1,2-diol (propylene glycol, PG) in three vehicle solutions: one normokalemic and made hypertonic with mannitol (HP5), one hyperkalemic but without mannitol (HP6), and one hyperkalemic and with mannitol (HP7). Subsequent function was assessed by autotransplantation. Up to 3 M glycerol in HP5 was well tolerated but not in HP6 or HP7. Conversely, up to 3 M PG in HP7 was compatible with excellent post-transplant function, but the same concentration in HP5 was severely damaging. PG (4 M) in either solution was severely injurious and no kidneys survived perfusion with this concentration. Vascular resistance was well controlled by the vehicle solutions with mannitol, but it was generally higher during perfusion with the hyperkalemic HP7 compared with the normokalemic HP5. No kidneys perfused with 3 M solutions of either of the cryoprotective agents and cooled briefly to -6 degrees C without freezing had any post-transplant function, and neither did kidneys perfused with 3 M PG or 4 M glycerol tolerate slow cooling to -80 degrees C and warming. The need to optimize perfusate composition for the CPA being used is clear, and the dramatic increase in toxicity of PG when the concentration exceeds 3 M supports the suggestion that mixtures of PG and glycerol should be considered. The observation of damage at high subzero temperatures, before freezing has occurred, requires further detailed study.

Perfusion of rabbit kidneys with solutions containing propane-1,2-diol

Propane-1,2-diol (propylene glycol, PG) permeates more rapidly than glycerol, has a strong glass-forming tendency, and appears to have a low toxicity. It is therefore attractive as a potential cryoprotectant for renal preservation. In this paper we compared the effect on subsequent function, of exposing rabbit renal cortical slices to 1 M PG or glycerol in a range of vehicle solutions and we demonstrated a remarkably low toxicity of PG at this concentration. Rabbit kidneys were then perfused with solutions containing PG up to a maximum concentration of 3 M, after which the cryoprotectant was removed and the function of cortical slices prepared from the perfused kidneys was assessed. Marked differences in perfusion characteristics were found between PG and glycerol and between different vehicle solutions for PG, but the two most suitable perfusates, both containing about 100 mM mannitol, permitted normal function in slices prepared after removal of PG. These results indicate that, with an appropriate vehicle perfusate, exposure to PG up to a concentration of 3 mol/liter has remarkably little effect upon vascular resistance and the renal cortical functions measured.

Functional preservation of the mammalian kidney. VI. Viability assessment of rabbit kidneys perfused at 25 degrees C with dimethyl sulfoxide in RPS-2

The study utilizes an ex vivo perfusion model to evaluate the effects of warm perfusion (25 degrees C) with two K+-rich vehicle solutions (RPS-2 and solution A) on whole rabbit kidneys. The suitability of the solutions as vehicles for introducing cryoprotectant concentrations (2.8 and 3.5 M) of dimethyl sulfoxide (Me2SO) and the effects of the addition of albumin to RPS-2 are also tested. Albumin (5 g/dl) does not appreciably improve the renal perfusion dynamics of RPS-2. Results indicate that both RPS-2 and solution A serve as effective vehicles for the introduction of 2.8 M Me2SO, and the continued investigation of the RPS-2/Me2SO protocol is advocated.

Rabbit kidney function in vitro: the effect of colloids, energy substrate, a vasodilator, perfusion pressure, and bovine serum albumin

An in vitro perfusion system at 37 degrees C for the assessment of rabbit kidney function is described. The purpose of this assay system is to evaluate the effects of cryobiological manipulation on kidney function. The effect of the colloids dextran (MW = 70,000, 80,000, and 180,000) in the perfusate at 110 mm Hg were compared to a reduced perfusion pressure, colloid-free perfusate. Better function was obtained at lower perfusion pressure with the colloid-free perfusate. Less damage was noted histologically on light and electron microscopy. Investigation of energy substrates on rabbit kidney function demonstrated that butyrate, or lactate, in addition to glucose resulted in increased sodium and glucose reabsorption over glucose alone. Substrate-free perfused kidneys exhibited depressed Na transport. Lactate, and to some extent butyrate, decreased net glucose utilization. An alpha-adrenergic blocking agent, isoxsuprine, in the initial flush solution did not appear to be beneficial. An increase of perfusion pressure from 50 to 75 mm Hg resulted in an increase in GFR. Tubular function was enhanced by inclusion of small amounts of BSA in the perfusate.

An alpha-adrenotropic study of the normal and diabetic rabbit kidney

Rabbit kidneys from normal and alloxan-treated animals were isolated and perfused at 30 degrees C, with Krebs-Henseleit solution. Norepinephrine (NOR), 1 microgram/min, promoted an increase in perfusion pressure which was blocked by phentolamine. In diabetic kidneys NOR induced a sluggish increase in perfusion pressure and resistance, showing a decrease in sensitivity of the adrenergic receptors to the drug. Propranolol, a beta-blocker, was able to elicit an alpha adrenergic blockade in diabetic kidneys. These facts demonstrate an adrenergic receptor defect in diabetic animals, which was shown just three weeks after alloxan treatment.

The effect of cold storage on the sensitivity to alpha and beta agonists in the isolated rabbit kidney

Rabbit kidneys were perfused at 25 degrees C, and the effect of alpha and beta agonists was studied, before and after 24 hr of cold storage. Vascular and in vitro functional parameters were evaluated. We concluded that cold storage impairs partially the vascular alpha receptor. We could not find beta receptors under these conditions. An electron microscope analysis of these kidneys has shown some degree of autolysis of the tubular cells and good preservation of the vascular smooth muscle cells and membranes. These results are very important for kidney preservation before transplantation.

Functional preservation of the mammalian kidney. IV. Functional effects of perfusion with dimethyl sulfoxide (DMSO) at normothermia

Rabbit kidney were perfused at 37degreesC with various concentrations of DMSO in a K+-Mg2+-rich perfusate. The effects of DMSO on various functional parameters of the rabbit kidney perfused for 60 min were compared with the functional effects of perfusion without DMSO under the same conditions. DMSO produced deviations in vascular resistance and perfusate flow rate from control values. In kidneys perfused with 1.4 and 2.8 M DMSO these vascular changes resulted in changes in GFR at relatively unchanged filtration fractions. The closely parallel relationship between changes in GFR and urine flow in all groups indicates that perfusion per se or perfusion with DMSO may shift the regulation of urine flow rate from tubular reabsorption, which obtains in the in vivo situation, to glomerular filtration. This view was supported by the relatively unchanged parameters of Na+ reabsorption and fractional water excretion during perfusion with all concentrations of DMSO. Additionally, DMSO perfusion resulted in significantly greater weight gains than those observed in kidneys perfused without DMSO, and significantly depressed clearances of PAH, with 2.1 and 2.8 M DMSO.