Unexplained acidosis of malnutrition: a study by ion-exchange chromatography/mass spectrometry

Keto-acidosis is usually associated with uncontrolled diabetes and typically poses few diagnostic problems when presenting as hyperglycaemia, metabolic acidosis and a high anion gap. An emaciated patient suffering from Duchenne Muscular Dystrophy and volume depletion presented with acidosis of unknown origin. Preliminary investigations appeared to rule out lactic acidosis, diabetic keto-acidosis and acidosis due to base loss. We have previously reported a technique utilizing liquid chromatography coupled to mass spectrometry (LC-MS) which can be used to characterize the underlying aetiology of acidosis and applied it to ultrafiltrate derived from a blood sample taken from this patient. The anion profile obtained on the chromatogram showed elevated levels of acetoacetate and hydroxybutyrate but no evidence of lactic acidosis, nor was the profile typical of that seen in 'unexplained' acidosis. We concluded that the patient was suffering from keto-acidosis associated with starvation and dehydration, the biochemical features being obscured by both the patient's chronic malnutrition and minimal muscle mass. A combination of enteral feeding and rehydration led to prompt resolution of the patient's metabolic acidosis.

Continuous venovenous haemofiltration for the treatment of theophylline toxicity

In patients with severe theophylline toxicity charcoal haemoperfusion is the recommended method for rapid reduction of serum theophylline levels. However, access to this technique is limited in most hospitals. This case report shows that continuous venovenous haemofiltration, a technique available in most hospitals, is an effective alternative to charcoal haemoperfusion.

Bicarbonate-based haemofiltration in the management of acute renal failure with lactic acidosis

Continuous haemofiltration with lactate-based replacement fluid is widely used for the treatment of acute renal failure (ARF). In the presence of lactic acidosis, such treatment exacerbates rather than improves the clinical state. Continuous haemofiltration using a locally-prepared bicarbonate-based replacement fluid was performed in 200 patients over 7 years. All the patients had ARF with concomitant lactic acidosis, or demonstrated lactate intolerance after starting haemofiltration with lactate-based replacement fluids. In every case it was possible to correct the acidosis without inducing either extracellular volume expansion or hypernatraemia. In 89 patients (45%), the lactic acidosis resolved while being treated with bicarbonate-based haemofiltration. Fifty-seven patients (28.5%) survived. Significant differences at presentation in the group who survived, compared with those who died, were seen in age (50.8 vs. 57.1), mean arterial pressure (68.5 vs. 60.0 mmHg) and APACHE II score (32.1 vs. 38.9). Neither the severity of the presenting acidosis nor the arterial blood lactate appeared to predict outcome. Patients who developed ARF and lactic acidosis after cardiac surgery had a low survival rate. The combination of ARF and lactic acidosis that cannot safely be treated by haemofiltration using lactate-based replacement fluids can be managed with bicarbonate-based haemofiltration.

Bicarbonate therapy and intracellular acidosis

1. The correction of metabolic acidosis with sodium bicarbonate remains controversial. Experiments in vitro have suggested possible deleterious effects after alkalinization of the extracellular fluid. Disequilibrium of carbon dioxide and bicarbonate across cell membranes after alkali administration, leading to the phenomenon of 'paradoxical' intracellular acidosis, has been held responsible for some of these adverse effects. 2. Changes in intracellular pH in suspensions of leucocytes from healthy volunteers were monitored using a fluorescent intracellular dye. The effect in vitro of increasing extracellular pH with sodium bicarbonate was studied at different sodium bicarbonate concentrations. Lactic acid and propionic acid were added to the extracellular buffer to mimic conditions of metabolic acidosis. 3. The addition of a large bolus of sodium bicarbonate caused intracellular acidification as has been observed previously. The extent of the intracellular acidosis was dependent on several factors, being most evident at higher starting intracellular pH. When sodium bicarbonate was added as a series of small boluses the reduction in intracellular pH was small. Under conditions of initial acidosis this was rapidly followed by intracellular alkalinization. 4. Although intracellular acidification occurs after addition of sodium bicarbonate to a suspension of human leucocytes in vitro, the effect is minimal when the conditions approximate those seen in clinical practice. We suggest that the observed small and transient lowering of intracellular pH is insufficient grounds in itself to abandon the use of sodium bicarbonate in human acidosis.

Magnetic resonance renography: optimisation of pulse sequence parameters and Gd-DTPA dose, and comparison with radionuclide renography

The aim of this study was to assess the feasibility of magnetic resonance renography (MRR) using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) in comparison with conventional radionuclide renography (RR) using technetium-99m-DTPA (99mTc-DTPA). MRR has many advantages over RR, including lack of ionising radiation, increased spatial resolution, and visible background anatomy. By optimising the pulse sequence, we developed an MRR protocol in which signal intensity is linear with Gd-DTPA concentration over a clinically relevant range. Twenty-nine patients and a volunteer were studied using this protocol. Magnetic resonance renography was performed using three different doses of Gd-DTPA: 0.1 mmol kg-1 (n = 13), 0.05 mmol kg-1 (n = 7), and 0.025 mmol kg-1 (n = 9). Each patient was also assessed using radionuclide renography. The resulting renograms were assessed in terms of time to peak signal intensity, signal decrease after peak, and kidney function ratios calculated from both the areas underneath and the slopes of the uptake curves. We have shown that the MR renograms obtained using low dose Gd-DTPA correlate best with the radionuclide renograms. Remaining discrepancies may be explained by variations in the injection procedures (hence in arterial input functions) and the limited coverage of the three MRR slices compared to the whole body projection of RR. Furthermore, at high local concentrations, signal becomes independent of T1 and is dominated by T2.

Free radical reactions involving the angiotensin converting enzyme inhibitor captopril

Using the pulse radiolysis technique, absolute rate constants have been obtained for the reaction of captopril with several free radicals. The results demonstrate that although captopril reacts rapidly with a number of free radicals, such as the hydroxyl radical (k = 5.1 × 10(9) dm(-3)mol(-1)s(-1)) and the thiocyanate radical anion (k = 1.3 × 10(7) dm(-3)mol(-1)s(-1)), it is not exceptional in this ability. Similarly, the reactions with carbon centred radicals although rapid are an order of magnitude slower than those observed with glutathione. Additional lipid peroxidation studies further demonstrate that captopril is a much less effective antioxidant than glutathione. The data go some way to supporting the view that any attenuation of reperfusion injury by captopril is not through a direct free radical scavenging mechanism but may be afforded by other, non-radical-mediated mechanisms.

An inhibitor of the sodium pump obtained from human placenta

BACKGROUND

Much effort has been expended in the search for an endogenous inhibitor of the cellular sodium/potassium pump, a compound of major physiological importance, which has been implicated in the mechanism of essential hypertension. Others have suggested that ouabain or an isomer of ouabain may be the endogenous pump inhibitor. Neonatal cord serum contains an inhibitor of the sodium pump; we attempted to isolate and characterise this substance from human placentas.

METHODS

Homogenised placentas were dialysed and the resulting solutes were trapped on octadecylsilyl silica and then separated by high-performance liquid chromatography. Measurement of the activity of the sodium pump of human leucocytes was used to test each fraction for the presence of the inhibitor.

FINDINGS

An inhibitor of the sodium pump was obtained by this technique in a mass spectrometrically pure form with a mass of 370 Da, an empirical formula of C24H34O3 and only one hydroxyl group. The characteristic fragmentation pattern observed in negative-ion mass spectrometry was compared with those of various model compounds; this comparison suggested that the active material was a dihydropyrone-substituted steroid.

INTERPRETATION

These results suggest that a dihydropyrone-substituted steroid is an endogenous regulator of the sodium pump in humans and, presumably, other mammals. Proof of the endogenous origin will require the demonstration of a previously unrecognised biosynthetic pathway.

Use of continuous haemofiltration to assess the rate of lactate metabolism in acute renal failure

1. Whole-blood lactate levels were measured at different rates of haemofiltration in 10 patients with acute renal failure undergoing conventional continuous haemofiltration using lactate-buffered replacement fluid. 2. The results enable both basal production rates and the metabolic clearance of lactate to be estimated in man.

Basic simulations for anaesthetists. A pilot study of the ACCESS system

This paper describes the design and initial testing of the ACCESS (Anaesthetic Computer Controlled Emergency Situation Simulator) system, which has been designed to simulate anaesthetic emergencies with the aim of providing training for junior doctors. The simulations require little or no capital expenditure with minimal use of time by staff or trainees. They are based on standard anaesthetic equipment, with a microcomputer providing an image of commonly used instruments. Problems are presented as scenarios administered by the teacher, and test the skills of the pupil. During 64 scenarios, five trainees caused two 'deaths' and solved the problems in a median time of 2.5 min, while an experienced group of anaesthetists caused one 'death' and took 1.8 min. The simulation was rated by the pupils as easy to use, realistic and a valuable educational tool.

Acute renal failure treated by haemofiltration: factors affecting outcome

Two hundred and fifty consecutive patients with acute renal failure treated by continuous haemofiltration on one intensive care unit (ICU) were studied prospectively to investigate the possibility of predicting outcome at the time of referral. Logistic regression analysis was used to identify important prognostic factors and the regression coefficients were used to weight a scoring system for the severity of illness of patients with acute renal failure. Overall survival was 53% with improvement over the course of the study. Multivariate analysis showed that outcome was related to age, need for artificial ventilation, use of inotropes, urine volume, serum bilirubin, arterial base deficit and serum creatinine. The scoring system based on the first five of these variables had a specificity of predicting death of 67% and a sensitivity of 76%.

Treatment of combined renal failure and lactic acidosis by haemofiltration

Twelve patients with renal failure and type A lactic acidosis were treated with haemofiltration during a 30-month period. The first three patients received only lactate-buffered replacement fluid and rapidly succumbed despite the infusion of large quantities of sodium bicarbonate. Bicarbonate-buffered replacement fluid was used for the remaining nine patients, of whom three survived. Haemofiltration with bicarbonate-buffered replacement fluid is an effective method of replacing renal function for this group of critically-ill patients.

Relationship between intracellular proton buffering capacity and intracellular pH

In a recent publication the widely held view that the intracellular proton buffering power [defined as the amount of acid or base that has to be added to the cytosol to change the intracellular pH (pHi) by one pH unit] increases as the intracellular pH decreases, has been challenged, with the opposite relationship being proposed. In that publication, buffering was defined not in terms of pH change, but in terms of the change in proton concentration. The reason for this re-definition was the fear that the conventional analysis, using as it does a logarithmic function (pHi), could bias the outcome in favor of an increasing buffering power with decreasing pHi. The new system uses a "buffering co-efficient," defined as the number of protons necessary to be added to the cytosol to change the intracellular proton concentration by 1 mM. We report the use of both of these methods to analyze the relationship of pHi and buffering power, using human peripheral leucocytes loaded with the pH-sensitive fluorophore BCECF examined over a very wide range of pHi values (pHi 6.0 to 7.5). The most common method for pHi perturbation for the measurement of buffering is used, the rapid diffusion of ammonia across the cell membrane. In this study, analysis for both a bicarbonate-containing "open" system and for a Hepes-buffered "closed" system was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Leucocyte intracellular pH and Na(+)-H+ exchange activity in essential hypertension: an in vitro study under physiological conditions

The cellular basis for essential hypertension remains obscure. Abnormal ion transport has been demonstrated in both experimental and essential hypertension, raised levels of sodium-lithium (Na(+)-Li+) and sodium-proton (Na(+)-H+) exchange in blood cells being a consistent feature. However, Na(+)-H+ exchange is not the main regulator of intracellular pH at resting pH, while the importance of the contribution of bicarbonate to cellular pH regulation is now increasingly appreciated. Serum and serum-derived growth factors are known to affect intracellular pH and the activity of the Na(+)-H+ antiporter. This study was designed to investigate the activity of Na(+)-H+ exchange in the leucocytes of patients with essential hypertension in the presence of bicarbonate in vitro and to measure the effect of autologous serum on intracellular pH and Na(+)-H+ exchange. Paired serum samples from essential hypertensives and their controls were used on leucocytes from other (unrelated, normotensive) donors to investigate the same parameters. In a study of 30 patients with untreated essential hypertension and 30 controls matched for age, sex, race and body habitus we found no difference in resting pH or buffering capacity (pH 7.28 +/- 0.01 and 32.0 +/- 1.6 mmol/l per pH, hypertensives, versus 7.27 +/- 0.02 and 34.5 +/- 1.8 mmol/l per pH, controls) but a marked difference in the maximal rate of Na(+)-H+ exchange in response to intracellular acidification (57.8 +/- 3.2 mmol/l per min versus 47.2 +/- 1.4 mmol/l per min, P = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Na+ transport in hypertension

Several different lines of argument lead to the conclusion that the Na+ ion is important in hypertension. These include dietary and epidemiological studies, studies on the isolated cells and tissues of hypertensive subjects, and the association of the genetic predisposition to hypertension with abnormalities of cellular Na+ handling. In isolated cells, the most convincing abnormalities have been shown in the Na+ pump, where there is also evidence of a circulating inhibitor of the pump in essential hypertension, although the nature of the agent is still uncertain. The genetic association between essential hypertension and Na+ transport is best represented by alterations in Na(+)-Li+ countertransport in hypertensive subjects and their near relatives, although interpretation is rendered more complex by the influence of nongenetic factors on this system. The demonstrated differences between hypertensive and nonhypertensive subjects in the cellular handling of Na+ have not been integrated into a totally convincing explanation of the ultimate mechanism of the condition. Attention has focused on the possible mechanisms whereby an increase in intracellular Na+ may increase the concentration of cytosolic Ca2+ in the vascular smooth muscle, which is presumed to be a necessary precondition to a chronically elevated peripheral vascular resistance.

Effect of autologous serum on human leucocyte Na+/H+ exchange and intracellular pH

1. Leucocyte Na+/H+ exchange and intracellular pH were investigated in physiological buffer containing bicarbonate. 2. The amiloride analogue 5-(N,N-hexamethylene) amiloride (1 x 10(-5) mol/l), an inhibitor of Na+/H+ exchange, had no significant effect on resting leucocyte pH, Na+ influx or Na+ content. 3. Ammonium chloride washout induced a profound intracellular acidosis, stimulating Na+/H+ exchange. This led to a 236% increase in Na+ influx. Eighty-eight per cent of this increase was inhibited by 5-(N,N-hexamethylene) amiloride. This demonstrates that 5-(N,N-hexamethylene) amiloride is an effective inhibitor of Na+/H+ exchange in human leucocytes. 4. The recovery from intracellular acidosis was shown to be dependent entirely on the presence of extracellular Na+. The Ki for inhibition by 5-(N,N-hexamethylene) amiloride of the recovery was 0.5 mumol/l. 5. Incubation with serum increased Na+ influx and Na+ content: the maximal effect was reached at 20% dilution. Serum (10%, v/v) increased influx by 40%, and 20% (v/v) serum by 102%, over resting levels. Only 43% of the serum-induced increase in Na+ influx was inhibited by 5-(N,N-hexamethylene) amiloride. This represented one-fifth of total Na+ influx. 6. Leucocyte intracellular pH increased on incubation with serum. This alkalinization was inhibited using 5-(N,N-hexamethylene) amiloride. 7. Studies of Na+/H+ exchange in leucocytes in physiological and pathological states are more likely to reflect the state in vivo if carried out in the presence of autologous serum.

Effects of ouabain and low sodium on contractility of human resistance arteries

Earlier work with rat arteries has resulted in a widely held assumption that resistance artery smooth muscle will not contract on exposure to a reduced transplasmalemmal sodium gradient. In view of the well-recognized low sensitivity of rat tissue to cardiac glycosides, we have investigated the effects of altering the transplasmalemmal sodium gradient on vascular smooth muscle tone by using human resistance arteries. Incubation of arteries in low sodium or in ouabain to inhibit active sodium efflux for 1 hour increased the contractile response to caffeine stimulation; this finding indicated enhanced calcium buffering by the sarcoplasmic reticulum. Prolonged incubation in ouabain in the presence of phentolamine or diltiazem resulted in a concentration-dependent increase in the tone of resting human resistance arteries. Reduction of the transplasmalemmal sodium gradient by incubation in low sodium buffer effected an increase in tone similar to that obtained in the presence of ouabain. These results suggest that alteration of the transplasmalemmal sodium gradient may increase the vascular smooth muscle tone of human resistance arteries by altering intracellular calcium handling. This is a new finding in human resistance arteries and may involve inhibition and, indeed, reversal of sodium-dependent calcium efflux. A concentration-dependent potentiation of tone was found after the addition of ouabain to submaximally activated arteries. Sodium-calcium exchange may also play a pivotal role in this mechanism.

A longitudinal study of maternal digoxin-like immunoreactive substances in normotensive pregnancy and pregnancy-induced hypertension

The serum of women in the third trimester of pregnancy demonstrates cross-reactivity with some commercially available antibodies to digoxin. A number of studies have suggested that levels of this digoxin-like immunoreactive substance(s) are further increased in patients with pregnancy-induced hypertension, and some have proposed that the digoxin-like immunoreactive substance could be useful as a predictor of pregnancy-induced hypertension. We measured digoxin-like immunoreactive substance levels every 2 weeks throughout the third trimester in 170 women; of these, 20 developed hypertension. Digoxin-like immunoreactive substance levels rose with gestational age. A graph of the slope of digoxin-like immunoreactive substance plotted against gestational age was fitted for the results obtained from each woman. There was no significant difference in the mean rate of increase of digoxin-like immunoreactive substance level per week between pregnancy-induced hypertension and normotensive pregnancy, nor was there any difference between these two groups at any gestational age studied. These results suggest that measuring digoxin-like immunoreactive substance levels is not useful as a predictor of pregnancy-induced hypertension.

Cyclosporin A inhibits endothelium-dependent, prostanoid-induced relaxation in human subcutaneous resistance vessels

The effect of cyclosporin on endothelium-dependent relaxation of human subcutaneous resistance vessels was investigated. Resistance vessels were obtained from normal subjects undergoing routine surgery. Acetylcholine-induced relaxation was shown to consist of at least two components, one mediated through vasodilatory prostanoids, the other through endothelium-derived relaxing factor (EDRF). Incubation with cyclosporin inhibited endothelium-dependent relaxation, as assessed by the response to acetylcholine. The inhibitory effect of cyclosporin on the acetylcholine response was most marked in the presence of methylene blue, which is an inhibitor of EDRF. This suggests that the inhibition of endothelium-dependent relaxation by cyclosporin is mediated by an effect on vasodilatory prostanoids.

Endothelin-induced contraction of human peripheral resistance vessels is partly dependent on stimulation of sodium-hydrogen exchange

The role of Na-H exchange in endothelin-induced contraction of human peripheral resistance vessels was investigated. Endothelin produced a dose-dependent contraction which was greatly attenuated in the presence of a low extracellular sodium concentration. Inhibition of Na-H exchange by the amiloride analogue 5-(N,N-hexamethylene) amiloride (5-NNHA) resulted in a greater than 65% relaxation of a maximal endothelin-induced contraction in the presence of normal extracellular sodium. However, in the presence of a low extracellular sodium concentration, inhibition of Na-H exchange only resulted in a 25% relaxation. These data suggest that endothelin-induced vasoconstriction of human peripheral resistance vessels is mediated in part by stimulation of Na-H exchange.

Serum digoxin-like substances in pregnancy-induced hypertension

1. Endogenous digoxin-like immunoreactivity (EDLI) was measured in the serum of 85 normotensive pregnant (NTP) women and 77 women with pregnancy-induced hypertension (PIH) by a radioimmunoassay (New England Nuclear). All women were in the third trimester. 2. EDLI, which was undetectable in serum from non-pregnant women, was present in NTP and PIH and was significantly higher in PIH. EDLI correlated with gestational age in NTP, but not in PIH. 3. Ouabain-sensitive Na+ transport was estimated in normal peripheral blood leucocytes after incubation with sera from 50 NTP and 42 PIH women. Significant inhibition of active Na+ transport occurred only with the serum of hypertensive patients without proteinuria. 4. EDLI did not correlate with the effect of the sera on active Na+ transport. The radioimmunoassay therefore provides a poor index of Na+ transport inhibitory activity in PIH.

Cyclosporine A inhibits relaxation but does not induce vasoconstriction in human subcutaneous resistance vessels

The effects of cyclosporine on the functional characteristics of human subcutaneous resistance vessels were investigated. Resistance vessels were obtained from normal subjects undergoing routine surgery. Incubation with cyclosporine did not alter the resting tone of the vessels, but decreased the maximum contractile response and the sensitivity of the vessels to stimulation with exogenous noradrenaline and potassium. Cyclosporine decreased the rate of spontaneous relaxation and inhibited endothelium-dependent relaxation as assessed by the response to acetylcholine. Paradoxically, endothelium-independent relaxation as assessed by the response to sodium nitroprusside was augmented. Hypertension induced by cyclosporine may, in part, be explained by a reduction in relaxation of peripheral resistance vessels.

A comparison of endogenous digoxin-like immunoreactivity and sodium transport inhibitory activity in umbilical arterial and venous serum

1. Endogenous digoxin-like immunoreactivity (EDLI) was measured by radioimmunoassay for digoxin in 13 paired samples of arterial and venous umbilical cord serum. EDLI was present in vein and artery, but was higher in the venous samples (P less than 0.025). 2. The venous cord serum inhibited the ouabain-sensitive sodium efflux rate constant of a normal mixed leucocyte population when compared with the effect of arterial cord serum (P less than 0.005). 3. It is suggested that the placenta may be involved in the production or metabolism of neonatal EDLI and of the inhibitor of sodium transport.

Evidence for an inhibitor of leucocyte sodium transport in the serum of neonates

1. In confirmation of previous studies, serum obtained from cord blood demonstrated endogenous digoxin-like immunoreactivity (EDLI). Sera from pregnant women in the third trimester also demonstrated EDLI, which disappeared after delivery. 2. Cord serum inhibited the total sodium efflux rate constant of a mixed leucocyte preparation when compared with the effect of control serum. This inhibition resulted from a depression of the ouabain-sensitive (sodium pump) component of the rate constant. 3. An ultrafiltrate of the serum (mol. wt. less than 30,000) also inhibited ouabain-sensitive leucocyte sodium transport when compared with filtrate obtained from control serum. 4. DHA-S Dehydroepiandrosterone sulphate (DHA-S) and cortisone, both present in high concentration in cord serum, demonstrated EDLI but did not affect leucocyte sodium transport in the cells of normal subjects. 5. DHA-S had no effect on sodium transport or vasoconstrictor activity in human omental resistance vessels. 6. It is concluded that EDLI of cord serum is associated with sodium transport inhibitory activity. This is unlikely to be attributable to DHA-S or cortisone.

Selective oxygen leak. A potential cause of patient hypoxia

A case is described where a patient received less oxygen than was set on the Rotameters. The cause was traced to a selective leak of oxygen via an open cyclopropane needle valve. Several recommendations are put forward to prevent a recurrence.

Effect of serum from patients with essential hypertension on sodium transport in normal leucocytes

This study has confirmed that serum from patients with essential hypertension inhibits sodium transport and elevates intracellular sodium in normal human leucocytes in vitro when compared with that of well matched normotensive controls. The magnitude of this effect was positively correlated with the diastolic blood pressure of the hypertensive patient. The degree of sodium transport inhibition conferred by the hypertensive's serum was correlated with the abnormal sodium transport in the hypertensive's own leucocytes. These results confirm the presence of a serum inhibitor of sodium transport in essential hypertension. The relationship between the inhibitory effect and severity of hypertension argues that it may be of mechanistic importance.

A resuscitation box for every anaesthetist?

The results are reported of a questionnaire which asks whether or not anaesthetists routinely carry any resuscitation equipment in their cars. A small, simple resuscitation box is described which is adequate for the majority of life-threatening situations.

Effect of the calcium antagonist verapamil on human leucocyte sodium transport in vitro

Sodium efflux rate constants and intracellular sodium were measured in leucocytes from healthy volunteers in the presence and absence of the calcium antagonist verapamil hydrochloride. Verapamil stimulated sodium pump activity and this effect was dependent on the presence of external calcium. Verapamil has been reported to reverse the abnormality of sodium transport seen in leucocytes from patients with essential hypertension and the present study demonstrates that sodium pump activity in leucocytes from control subjects is also stimulated by exposure to verapamil in vitro. This direct cellular effect appears to be due to the calcium antagonist properties of the drug.

Sodium pump activity in thymocytes of rats with Goldblatt hypertension

Sodium transport has been studied in thymocytes of one-kidney, one-clip (1K, 1C) and two-kidney, one-clip (2K, 1C) models of hypertension in the rat. No differences of intracellular sodium or sodium transport could be demonstrated in either model when compared with sham-operated controls. The experiments provide no evidence to support the concept that an inhibitor of sodium transport is associated with the development of hypertension in the one-kidney, one-clip rat. A previously unrecognized effect of incubation time and cell density on thymocyte sodium metabolism is reported.

Frusemide-sensitive sodium and potassium transport by human leucocytes

Frusemide-sensitive sodium and potassium transport by normal human leucocytes has been studied in vitro by both isotopic and net flux techniques. In physiological media the leucocyte exhibits a frusemide-sensitive influx of sodium and potassium of equal magnitude compatible with a 1:1 co-transport system. Cells exposed to zero external sodium and potassium (osmolality maintained with choline) demonstrated a frusemide-sensitive sodium and potassium efflux. Frusemide-sensitive potassium influx was dependent on the presence of external sodium but frusemide-sensitive sodium influx persisted unchanged in the absence of external potassium. Frusemide-sensitive potassium influx was dependent on external chloride but frusemide-sensitive sodium influx was chloride-independent. These last two observations make it likely that the frusemide-sensitive pathway is capable of operating in modes other than sodium-potassium co-transport.

Sodium transport by leucocytes and erythrocytes in hypertensive subjects and their normotensive relatives

Intracellular sodium content and ouabain-sensitive sodium efflux rate constant were measured in leucocytes and erythrocytes from subjects with untreated essential hypertension and also in normotensive subjects with and without a family history of hypertension. Leucocytes from hypertensives were again shown to have a higher intracellular sodium content and lower ouabain-sensitive sodium efflux rate constant than normotensive controls but there were no differences between those normotensive subjects with and those without a family history of hypertension. No differences in erythrocyte sodium content or efflux rate constant were seen between any of the three groups.

Parenteral acyclovir therapy for cytomegalovirus infection after renal transplantation

Three patients who had received cadaveric renal transplants developed fevers within three months of transplantation. Concurrent cytomegalovirus infection was confirmed by virological studies. In all three patients there was both a clinical and virological response to a five day course of intravenous acyclovir. In one patient the dose required to produce this response was 5 mg/kg/day; however two patients required 10 mg/kg/day. All three patients remain well after 8-12 months follow-up.

Reversal by verapamil of defect in sodium transport in leucocytes in essential hypertension

The effect of treatment with verapamil on cell sodium transport was studied in the leucocytes of patients with essential hypertension. Previously described abnormalities of sodium efflux rate constant and intracellular sodium content were confirmed, the component of the sodium efflux rate constant sensitive to ouabain being lower and the intracellular sodium content higher in the patients compared with controls. Verapamil reversed these abnormalities and reduced blood pressure.