Selective renal vasoconstriction, exaggerated natriuresis and excretion rates of exosomic proteins in essential hypertension

AIM

In essential hypertension (EH), the regulation of renal sodium excretion is aberrant. We hypothesized that in mild EH, (i) abnormal dynamics of plasma renin concentration (PRC) and atrial natriuretic peptide (ANP) are responsible for the exaggerated natriuresis, and (ii) exosomic protein patterns reflect the renal tubular abnormality involved in the dysregulation of sodium excretion.

METHODS

After 2-week drug washout and 4-day diet, systemic and renal hemodynamics, cardio-renal hormones, glomerular filtration and renal excretion were studied in male patients during saline loading (SL). Excretion rates of exosome-related urinary proteins including apical membrane transporters were determined by proteomics-based methods.

RESULTS

In patients, baseline renal vascular conductance was reduced (-44%, P < 0.001), but non-renal vascular conductances were normal while PRC was reduced and ANP elevated (both P < 0.01). SL induced exaggerated natriuresis and reduced PRC (P < 0.01), at normal suppression rate. SL increased arterial pressure in patients (+11 mmHg, P < 0.001), but not in controls; however, during time control, patients showed identical increases (+10 mmHg, P < 0.005) apparently dissociating arterial pressure from natriuresis. At baseline, excretion rates of 438 proteins ranged from 0.07 to 49.8 pmol (mmol creatinine)(-1); 12 proteins were found in all subjects, and 21 proteins were found in two or more patients, but not in controls. In patients, the excretion rate of retinoic acid-induced gene 2 protein was reduced, and excretion rates of other proteins showed increased variances compatible with pathophysiological and clinical applicability.

CONCLUSION

Essential hypertension patients exhibit selective renal vasoconstriction and individually varying excretion rates of several exosome-related proteins. Hormonal changes, rather than arterial pressure, seem to cause exaggeration of natriuresis.

Low-dose spironolactone reduces plasma fibulin-1 levels in patients with type 2 diabetes and resistant hypertension

Diabetic patients with hypertension are at particularly high risk of vascular damage and consequently cardiovascular and renal disease. Fibulin-1, an extracellular matrix glycoprotein, is increased in arterial tissue and plasma from individuals with type 2 diabetes. This study aimed to evaluate whether antihypertensive treatment with spironolactone changes plasma fibulin-1 levels. In a multicenter, double-blind, randomized, placebo-controlled study, 119 patients with type 2 diabetes and resistant hypertension were included. A dose of spironolactone 25 mg or matching placebo was added to previous treatment at randomization. Blood pressure (BP) and plasma fibulin-1 were measured at baseline and at 16 weeks follow-up. Overall, 112 patients completed the study. All measures of BP were reduced in the spironolactone group at follow-up. Plasma fibulin-1 was significantly reduced after spironolactone treatment (P=0.009), but increased after placebo (P=0.017). Baseline plasma fibulin-1 correlated with BP and estimated glomerular filtration rate. Increased levels of plasma fibulin-1 (P=0.004) were observed in diabetic participants reporting erectile dysfunction as compared with participants who did not. Treatment with low-dose spironolactone reduced plasma fibulin-1 levels in patients with type 2 diabetes and resistant hypertension. This supports the hypothesis that the antihypertensive effect of the mineralocorticoid receptor blocker in part may be due to regression of vascular remodeling.

Socio-economic status influences blood pressure control despite equal access to care

OBJECTIVE

Denmark has a health care system with free and equal access to care irrespective of age and socio-economic status (SES). We conducted a cross-sectional study to investigate a possible association between SES and blood pressure (BP) control of hypertensive patients treated in general practice.

METHODS

We enrolled 184 general practices and 5260 hypertensive patients. The general practitioners reported information about BP and diagnosis of diabetes. Information about education, income, antihypertensive drug treatment and other co-morbidity was retrieved from relevant registers from Statistics Denmark. The outcome measure was BP control defined as BP <140/90 mmHg in general and <130/80 mmHg in diabetics.

RESULTS

Patients <65 years and with an educational level of 10-12 years had increased odds ratio (OR) of BP control compared to patients with an educational level <10 years. Patients ≥65 years had increased OR of BP control if they were married/cohabiting as compared to being single, whereas education and income had no impact in this age group. Diabetics had significantly reduced odds of BP control irrespective of age, educational or income level.

CONCLUSIONS

Despite equal access to care for all patients, SES had significant impact on BP control in this survey. Diabetes and cardiovascular disease also had a substantial influence irrespective of age, educational and income level.

Treatment of 5413 hypertensive patients: a cross-sectional study

BACKGROUND

Most hypertensive patients are managed in primary care in Denmark, but previous studies have shown that only 21-43% of hypertensive patients achieve optimal blood pressure (BP) control. Antihypertensive drug treatment, risk factors and cardiovascular disease (CVD) are some of the important factors to consider when optimizing the individual treatment strategy in hypertensive patients.

OBJECTIVE

To examine treatment of BP according to Danish guidelines (BP < 140/90 mmHg generally and <130/80 mmHg for diabetics) in a population from general practice in relation to risk factors, CVD and diagnosis of diabetes.

METHODS

A cross-sectional study comprising 184 practices and 5413 hypertensive patients was carried out in Denmark. The general practitioners filled in information on each patient's risk factors, CVD and antihypertensive drug treatment. Patients filled in a questionnaire on risk factors. The outcome measures were optimal BP control according to Danish guidelines and antihypertensive drug treatment.

RESULTS

Mean patient age was 65.9 years [95% confidence interval (CI): 65.6-66.1]. Optimal BP control was achieved in 29.1% (95% CI: 27.9-30.3) of the study population. Among 842 diabetics with or without CVD, optimal BP control was achieved in 10.9% (95% CI: 8.8-10.3), while 38.7% (35.5-41.9) of patients with CVD achieved optimal BP control. The majority of all patients were treated with 1 (32.5%, 95% CI: 32.5 (31.3-33.8)) or two antihypertensive drugs (39.0%, 95% CI: 38.2-40.8). In hypertensive diabetics, 17.7% were not treated with an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker.

CONCLUSION

In general practice, the proportion of hypertensive patients achieving optimal BP control is inadequate. The majority of hypertensive patients are treated with only one or two antihypertensive drugs.

Tracking and factors predicting rising in 'tracking quartile' in blood pressure from childhood to adulthood: Odense Schoolchild Study

This prospective study determines the degree of tracking and investigates factors predicting a rise in blood pressure (BP) quartile in a cohort of 1369 subjects who were followed for 11 years from childhood into young adulthood. In 900 of these subjects BP, height, weight, physical fitness and BP responses to a maximal exercise testing were measured both at baseline and at follow-up. BP, weight, height and body mass index (BMI) were divided into sex-specific quartiles at both examinations. Tracking was evaluated by examining the tendency of remaining in the same quartile from baseline to follow-up and by measuring product-moment correlation coefficients. Tracking in the upper and lower quartile for BP, weight, height and BMI were significant. Odds ratios for staying in the upper or lower quartile through the follow-up period ranged from 1.6 to 2.4 for diastolic BP and from 2.1 to 3.1 for systolic BP. The range of correlation coefficients for the anthropometric measurements were 0.57-0.75, for diastolic BP 0.12-0.22 and for systolic BP 0.34-0.36 respectively. Changes in weight or relative weight as well as BP response to an exercise test were the factors which predicted a rise in quartile through the 11 years of follow-up. The existence of the inevitable regression to the mean problem in large longitudinal studies of BP was demonstrated by the finding of baseline BP being a significant factor in the prediction of rising in systolic, diastolic or both systolic and diastolic BP quartiles.

Ambulatory blood pressure in 570 Danes aged 19-21 years: the Odense Schoolchild Study

Ambulatory blood pressure (ABP) measurements were performed in a Danish population of 295 males and 275 females aged 19-21 years. Individualised day and night periods were defined from the subjects own recording of bedtime and rising on the day of their ABP measurements. During these individualised periods the ABP values for daytime, night-time and for the whole 24-h period were measured. The mean +/- s.d. values for systolic/diastolic ABP for the whole population were (124+/-11)/(70+/-7) mm Hg in the daytime, (106+/-12)/(60+/-9) mm Hg in the night-time, and (120+/-11)/(68+/-7) mm Hg in the whole 24-h period. Males had a mean systolic ABP of 9 mm Hg and mean diastolic ABP of 5 mm Hg higher than females. In males mean +/- s.d. systolic/diastolic ABP values in the daytime were (129+/-10)/(73+/-7) mm Hg, in the night-time (111+/-12)/(63+/-8) mm Hg, and in the whole 24-h period (125+/-10)/(71+/-7) mm Hg. The corresponding values in females were (119+/-10)/(68+/-6) mm Hg, (103+/-11)/(57+/-8) mmHg, and (115+/-10)/(66+/-6) mm Hg, respectively. In conclusion this study provides sex-specific normal values for ABP in a 19 to 21-year-old age group based on individualised daytime and night-time periods.

Crossover comparison of the pharmacokinetics of amlodipine and felodipine ER in hypertensive patients

The pharmacokinetics of amlodipine 5 mg and felodipine ER (extended release) 5 mg o.d. after single and 2 weeks of repeated oral doses, were compared in 28 essential hypertensive patients using a crossover design. As a secondary parameter the effects of the drugs on blood pressure were assessed. Significant differences were found between all principal pharmacokinetic variables, when comparing the 2 treatments after both single and repeated dosing. The coefficients of variation of maximal drug concentration and AUC after single dosing and at steady-state were significantly higher for felodipine ER than for amlodipine. After repeated dosing the peak-to-trough plasma concentration ratio were 1.58 and 4.43 (p < 0.001) for amlodipine and felodipine ER, respectively. Both drugs lowered systolic and diastolic blood pressure to the same extent after 2 weeks of repeated dosing. No significant differences between the blood pressure lowering vs time profile of the 2 drugs were encountered. In conclusion, the interpatient drug concentration variability and the peak-to-trough plasma concentration ratio were more favorable for amlodipine compared to felodipine ER. It remains to be established whether these characteristics are also reflected in a more smooth and consistent blood pressure control.

[Continuing medical education via questionnaire studies. Three pilot projects for anesthesiology, cardiology and neurology]

The Danish Medical Association and the scientific societies have initiated three studies to evaluate the use of questionnaires for continuous medical education. One study was a questionnaire in anaesthesiology with 30 questions with answers yes/no/no answer, which was sent to 600 specialists in anaesthesiology. One study was in cardiology with a multiple choice questionnaire, sent to 300 general practitioners and 75 specialists in internal medicine outside cardiology. One study concerned the educational value of State-of-the-Art articles about neurology in Ugeskrift for Laeger (Journal of the Danish Medical Association) sent to 500 doctors outside neurology. All questionnaires were sent anonymously, with one general reminder. For the anaesthesiology study 234 questionnaires were returned (40.5%). In the cardiology study 195 questionnaires were returned (52%). For the study on neurology 278 answered (56%). Only about half of the questionnaires were returned for the three studies, and a lot of effort and resources were put into the studies. An extension from these small pilot studies to a general systematic continuous methodology with updated questionnaires in the postgraduate medical education seems troublesome. An optional self-registration for medical education such as The Canadian "Mocomp concept" might be a more realistic suggestion.

Angiotensin converting enzyme inhibitor therapy and acute pancreatitis

Angiotensin converting enzyme (ACE) inhibitors are generally well tolerated. Worldwide, only few reports have been published associating pancreatitis with ACE inhibitor therapy. We report a case in whom there was no other likely explanation for the acute pancreatitis than enalapril therapy, which was temporally associated with the symptoms. Possible mechanisms underlying the induction of pancreatitis by ACE inhibitors are discussed. With the increasing use of ACE inhibitors, the incidence of rare adverse effects such as potentially lethal pancreatitis is likely to increase. Clinicians need to be aware of this association.

Preservation of rabbit kidneys using a solution containing hydrolyzed starch

An organ preservation solution has been developed by combining some features of the hypertonic citrate formulation of Ross, Marshall, and Escott (RME) with some features of UW solution. Specifically the solution (HP16) contains a balance of cations similar to that in RME and the same concentration of citrate, but sulfate is replaced by chloride and mannitol by a starch hydrolysis product (SHP). A gelatin-derived polypeptide (Haemaccel) is included to provide colloid osmotic pressure. The objective was to increase the effectiveness of RME by using a higher-molecular-weight osmoticum than mannitol, but avoiding the expense of raffinose; reducing the osmolality to a more physiological level; and including a colloid to make the solution suitable for continuous perfusion. The effectiveness of the solution was tested by 48-hr hypothermic preservation of rabbit kidneys. The results were compared with those obtained using RME or UW. It was shown that simple hypothermic storage was more effective than continuous perfusion, and that HP16 was more effective than RME and as effective as UW. The improvement over RME was ascribed to the isotonic osmolality and the inclusion of a higher-molecular-weight osmoticum (the SHP), possibly supplemented by the colloid (Haemaccel). Two SHP preparations, both with dextrose-equivalent values of approximately 35, were equally effective. These materials contain a standardized mixture of dextrose, maltose, and tri- and oligosaccharides, and have the osmotic properties of a trisaccharide. The results provide a new, inexpensive preservation solution that is as effective as any so far tested with this model, and they support the importance of appropriate osmotic properties for solutions to be used in organ preservation.

[Treatment of chronic occupational lead poisoning with dimercaptosuccinic acid (DMSA)]

2,3-dimercaptosuccinic acid (DMSA) mobilizes lead from superficial depots. In comparison with other chelating agents, DMSA has a high therapeutic index and has the additional advantage that it can be administered orally. We have used DMSA for treatment of chronic occupational lead poisoning in a 54-year old male with signs of neurotoxic effects. The treatment resulted in a rapid decrease in the blood-lead concentration, followed by a slow increase after the treatment and subsequent stabilization at a blood-lead level lower than prior to treatment. During the first course of treatment, almost 100 mumols lead was excreted in the urine. As a result of successive courses of treatments, the patient's condition was improved. However, during the third course of treatment, he developed a mucocutaneous rash which faded again after withdrawal of DMSA; this reaction was subsequently provoked by sub-therapeutic doses, and continued treatment was therefore cancelled. Only minor, reversible side effects of DMSA have hitherto been reported, and DMSA must therefore be regarded a promising agent for long-term, out-patient chelation treatment of chronic lead poisoning.

Chronic lead poisoning treated with dimercaptosuccinic acid

A 54-year-old male with chronic lead poisoning was treated with 2.3-dimercaptosuccinic acid (DMSA). A daily dosage of 30 mg/kg body weight for three days and 20 mg/kg for four days resulted in a decrease of the blood-lead concentration (B-Pb) from 3.7 to 0.7 mumol/l; the total amount of lead excreted in the urine during the first seven 24 hr periods was 75 mumol. After the treatment, B-Pb slowly increased to 3.3 mumol/l. A second treatment was then initiated and resulted in similar changes in B-Pb. However, during the third treatment, the patient developed a mucocutaneous vesicular flare; the eruptions faded after cessation of the chelation therapy, but could be provoked by DMSA doses of 10 mg/kg and above. Despite the small number of treatment courses, the patient showed obvious mental improvement and reported less headache and improved memory. Thus, DMSA is an efficient chelator that results in a rapid, though temporary decrease in B-Pb. Although oral treatment with this chelator may be supervised from the out-patient clinic, careful monitoring for potential side effects is recommended.

Hypothermic preservation of rabbit kidneys for 48 hours using low ionic strength solutions

Microwaves offer the prospect of rapid and uniform heating of frozen organs. This is significant in the context of cryopreservation, and particularly of vitrification, because microwave heating may help to avoid crystallization or recrystallization of ice during warming, minimize any effects of high cell density, and reduce thermal-mechanical stresses. Previous work has established a rationale for reducing the ionic strength of solutions used to prepare tissues for microwave heating, since this permits the use of lower frequencies, which makes heating more uniform, without increasing the risk of thermal runaway (T. P. Marsland, S. Evans, and D. E. Pegg, Cryobiology 24, 311-323, 1987). In this paper we report a study of two possible low ionic strength perfusates, in rabbit kidneys, using 48 hr of hypothermic storage and autotransplantation as the test system. This model was chosen because there is a great deal of basic information about it. Both a single-pass "flush" preservation solution and a solution designed for continuous perfusion gave excellent results. The continuous perfusion system, which would be the more suitable for introducing cryoprotectants, gave five of five surviving animals with peak serum creatinine levels of 353-555 mumol/liter normal histology in three cases, and only very minor damage in the other two. There would therefore seem to be no obstacle to the use of perfusates having a low ionic strength in renal cryopreservations studies.

[Treatment of acute chloroquine poisoning]

Acute chloroquine poisoning is life threatening with risk of death from apnoea and cardiac arrhythmia within a few hours of ingestion. Mechanical ventilation, infusion of pressor agents and large doses of diazepam seem to provide effective treatment. This treatment was introduced by Riou et alii (N Engl J Med 1988; 318; 1-6), and we used it successfully in a case of severe chloroquine poisoning. Intensive treatment was given during the first two days of intoxication, when the whole blood chloroquine phosphate concentration was high (more than 10 mumol/kg), corresponding to absorption from the gut and distribution to the organs. Hereafter the whole blood chloroquine phosphate concentration decreased increasingly slowly, probably due to equilibrium with tissue stores.

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.

Optimization of a vehicle solution for the introduction and removal of glycerol with rabbit kidneys

Previous studies with rabbit kidneys in our laboratories have used a plasma-like solution as the vehicle for the introduction and removal of glycerol. Other workers have usually employed high-potassium solutions. In this study we have assayed the function of rabbit renal cortical slices after incubation in a range of solutions, each of which contained 1 M glycerol, for 4 hr, followed by stepwise removal of the cryoprotectant. The functions measured were endogenous oxygen consumption, p-aminohippurate uptake, and the ability of the slices to accumulate potassium. Exposure to glycerol produced a considerable reduction of slice function, but, in the presence of glycerol, elevation of the potassium concentration was beneficial, whereas high concentrations of magnesium were detrimental. The optimum potassium concentration was 70-100 mM. Replacement of chloride by a range of anions of higher molecular weight was either without benefit (glycerophosphate) or detrimental (sulfate, citrate, and gluconate). Elevation of total osmolality from 300 to 400 mosmolal with glucose, mannitol, glycerophosphate, or Pipes reduced slice function, but when the same osmolality was achieved by raising the concentration of all the components of the solution in the same ratio, there was no significant loss of function. There was a weak optimum pH at ca. 7.0. These experiments led to the formulation of a bicarbonate-buffered perfusate containing 80 mM potassium and 17.5 g Haemaccel per liter, having a pH of 7.0 with 5% CO2 at 10 degrees C, and an osmolality of 400 mosmol/kg. This solution was used to preserve rabbit kidneys for 20 hr at 10 degrees C, by continuous perfusion, and was compared with our previous Haemaccel perfusate, HP5, which contained 4 mM K+, 111 mM mannitol, and had a pH of 7.4. The two solutions were equally effective.

Effect of cooling and warming rate on glycerolized rabbit kidneys

Cooling and warming rates are known to be important determinants of viability for cryopreserved cells, but optimal rates have not previously been determined for any whole organ. In this study, rabbit kidneys, permeated with 2 M glycerol were cooled to -80 degrees C at four rates varying from 1 degrees C/hr to 3.1 degrees C/min and then rewarmed at four rates from 1 degrees C/hr to 4.2 degrees C/min, giving 16 experimental treatments. After gradual deglycerolization at 10 degrees C, each kidney was autografted and observed for 30 min. Assessment was by measurement of vascular resistance, immediate post-thaw lactate dehydrogenase (LDH) release, gross appearance, light- and electron microscopy, and tissue K+/Na+ ratio 30 min after transplantation. The best results were obtained after cooling at 1 degrees C/hr; warming rate had little apparent influence on the criteria used to assess function with the exception of LDH release, which indicated a preferred warming rate around 1 degrees C/min. Histological studies revealed extensive vascular damage, notably to the glomerular capillaries, that was minimized by very slow cooling. Freeze substitution, carried out on samples removed at -80 degrees C, demonstrated extensive ice formation in the interstitial space and, at the faster cooling rates, in the glomerular capillaries. Intracapillary ice formation was reduced in the kidneys cooled at 1 degrees C/hr.

The effect of cooling and warming rate on cortical cell function of glycerolized rabbit kidneys

Experiments previously reported (I.A. Jacobsen, D.E. Pegg, H. Starklint, J. Chemnitz, C.J. Hunt, P. Barfort, and M.P. Diaper, Cryobiology 19, 668, 1982) suggested that rabbit kidneys permeated with 2 M glycerol are least damaged during freezing and thawing if they are cooled very slowly (1 degree C/hr). Using similar techniques of glycerolization, cooling, storage at -80 degrees C, rewarming, and deglycerolization, active cell function in cortical tissue slices prepared from such kidneys has now been studied. Oxygen uptake, tissue K+/Na+ ratio after incubation, and slice/medium PAH ratio after incubation were measured. Kidneys cooled at 3.1 degree C/min and warmed at 4.2 degrees C/min gave poor results in the previous studies and the lowest levels of cell function in the present experiments. Kidneys cooled at 1 degree C/hr exhibited degrees of slice function that were dependent on warming rate: warming at 1 degree C/min was better than warming at either 1 degree C/hr or c.20 degrees C/min. These results refine the previously drawn conclusions, (loc cit) and indicate optimal cooling and warming rates for rabbit kidneys containing 2 M glycerol, in the region of 1 degree C/hr cooling and 1 degree C/min warming. These rates are much lower than have hitherto been used by others for any system. Some implications of these findings are discussed.

Renal transplantation in the rabbit: a model for preservation studies

Transplantation is necessary for evaluation of kidney preservation procedures, and a model using a small laboratory animal is desirable. The rabbit was found to be a suitable animal for this purpose. Even long periods of anaesthesia without artificial respiration were safely achieved. Hydration and serum electrolytes could be maintained within normal ranges with intravenous injections of isotonic saline and dextrose during and after the operation. The kidneys were implanted by anastomosing the artery and vein end-to-side to the abdominal aorta and the posterior vena cava respectively. The ureter was implanted into the bladder over a nylon stent. In a recent 100 transplantations the incidence of vascular thrombosis was low (4%), but rather more (10%) mainly late ureteral complications were encountered. Transplanted kidneys showed good function with mean peak serum creatinines of 285 mumol/l and normal macroscopic and histological appearance at autopsy.

A new solution for initial perfusion of transplant kidneys

There is good evidence that blood should be removed from kidneys as completely as possible before they are transplanted. Rabbit kidneys, either freshly isolated or after one hour of warm ischaemia, were perfused with a solution of osmolality 400 mOsm/kg which contained high concentrations of Mg++ (72 mEq) and glucose (167 mM). The rate and completeness of blood removal were measured by collecting effluent fractions until 100 ml had been perfused, and then assaying the haemoglobin in each effluent fraction and the residual haemoglobin in the kidney. A pressure of 60 mmHg was found to be sufficient for effective perfusion. The addition of 5% dextran 40 (Rheomacrodex) to the perfusate greatly improved the completeness of blood removal from kidneys subjected to one hour of warm ischaemia. Rabbit kidneys washed out with this solution functioned excellently after transplantation.

Hypothermic perfusion of rabbit kidneys with solutions containing gelatin polypeptides

Rabbit kidneys were perfused with a solution of extracellular electrolyte composition, made hypertonic with glucose and containing the gelatin polypeptide preparation Haemaccel (Hoechst) as the only colloid. Perfusions were carried out at 5 and 10 C for 19 hr, and function was tested by autografting. All of the kidneys perfused at the higher temperature showed immediate life-sustaining function after transplantation and contralateral nephrectomy, whereas only one graft of five perfused at the lower temperature showed any function. The suitability of the Haemaccel solution as a vehicle for introducing the cryoprotective agent glycerol was tested by perfusing kidneys for 4 hr with a solutiont containing 2% glycerol; the function of these organs was similar to that of kidneys transplanted without perfusion. Ultrastructural examination of kidneys perfused for 24 hr at 10 C showed excellent structural preservation, but measurements of water and ion contents and the penetration of marker molecules in nonmetabolizing kidneys showed 2.8% Haemaccel to be somewhat less effective than 6% bovine serum albumin in stabilizing these values. The Haemaccel perfusate is considered to be highly suitable for the introduction and removal of cryoprotective agents, and the results of hypothermic preservation by continuous perfusion are encouraging.

Prolongation of xenograft survival by infusion of heterologous antibodies against recipient serum

Survival or renal xenografts from rabbit to cat has been prolonged by several hours by injection of antibodies against cat serum into the recipient. In control experiments the transplanted rabbit kidney was rejected by the cat in a few minutes.

LDH release into perfusates of preserved kidneys

The measurement of lactate dehydrogenase (LDH) release into perfusates after hypothermic storage was found to be a reliable index of ischemic injury of rabbit kidneys. Kidneys were exposed to warm and cold ischemia for varying periods. Each kidney was perfused before and after storage at simple hypothermia with 25 ml of a modified Collins solution. The venous effuent was collected in 5 ml fractions. Total LDH activity was measured in the first fraction after storage and used as a measure of ischemic tissue damage. It was confirmed that increasing the period of cold ischemia result in significant increases in LDH activity. The release of LDH into perfusates was then used to compare kidney damage after preservation with various fluids. With this method, it was not possible to demonstrate any difference in the extent of tissue damage after preservation with sodium-rich vs. potassium-rich perfusion fluid. Addition of steroids, vitamins and essential amino acids did not prevent or reduce tissue damage, estimated in this way. The effects of adding cryoprotectants to the perfusion fluid varied; LDH release following addition of 5% DMSO was significantly greater, and after addition of 5% glycerol smaller than the release after perfusion with a modified Collins solution alone. Stepwise addition of DMSO up to 20% resulted in serious tissue damage with a large LDH release into the perfusate.