Long-term safety and efficacy of intramyocardial adenovirus-mediated VEGF-DΔNΔC gene therapy: eight-year follow-up of phase 1 KAT301 study

Backgound/Introduction

In phase I KAT301 trial, adenovirus-mediated intramyocardial vascular endothelial growth factor-DΔNΔC (VEGF-D) gene therapy (GT) resulted in a significant improvement in myocardial perfusion reserve and relieved angina at 1-year follow-up without major safety concerns.

Purpose

Our objective was to investigate the long-term safety and efficacy of AdVEGF-D GT. A total of 30 patients (24 VEGF-D and 6 randomized and blinded controls) participated in KAT301 trial.

Methods

The mean follow-up time was 8.2 years (range 6.3–10.4 years). Patients were interviewed for the current severity of symptoms (Canadian Cardiovascular Society class, CCS) and perceived benefit from GT. Medical records were reviewed to assess the incidence of major cardiovascular adverse events (MACEs) and other predefined endpoints including cancer.

Results

MACE occurred in 15 patients in VEGF-D group and in five patients in control group (21.5 vs. 24.9 per 100 patient-years; hazard ratio 0.90; 95% confidence interval 0.09–9.32; P=0.95). Mortality and comorbidity were similar between the groups. Angina symptoms (CCS) were less severe compared to baseline in VEGF-D group (1.9 vs. 2.9; P=0.006) but not in control group (2.2 vs. 2.6; P=0.414).

Conclusion(s)

Our study indicates that intramyocardial AdVEGF-D GT is safe in the long-term. In addition, the relief of symptoms remained significant during the follow-up.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Kuopio University Hospital Heart Center Figure 1. The incidence of MACEFigure 2. CCS class

AB0056 NATURAL ANTIBODIES AGAINST PHOSPHORYLCHOLINE AND MALONDIALDEHYDE DURING THE FIRST TWO YEARS OF LIFE: IMPLICATIONS FOR RHEUMATIC DISEASE

Background:

Antibodies against phosphorylcholine (anti-PC) have potentially protective properties in both atherosclerosis and rheumatic disease. IgM anti-PC could play a role in SLE being associated with protection, also in relation to atherosclerotic plaques and vulnerable plaques in SLE1and being a non-responder to biologics in RA.1We reported potential mechanisms by which anti-PC could be protective: 1:anti-inflammatory; 2: inhibits uptake of oxLDL in macrophages, 3: inhibits cell death.14: anti-PC (and anti-MDA) increases clearance of human dead cells which could be of importance not especially in SLE;25: anti-PC increases T regulatory cells in SLE-patients´ T cells from a low level and also in atherosclerosis, with implications for both conditions.3Also antibodies against malondialdehyde (anti-MDA) have interesting properties

Objectives:

It is not known how these antibodies develop early in life and what may cause low levels. The objective is to determine this.

Methods:

Antibodies were studied by ELISA in healthy pregnant women (n=105; Born into life study) and their newborn children. Women were recruited before conception. Informed consent, questionnaires from parents and plasma sample was collected from children at birth from cord blood, at 1-year and 2 years after birth. Extracted antibodies were compared using a proteomics de novo sequencing approach.

Results:

Children were born with very low levels of IgM anti-PC, while IgM anti-MDA was present at birth,. Both IgM anti-PC and anti-MDA increased during the first two years of life, but IgM anti-PC in contrast to IgM anti-MDA was still significantly lower than mothers´. IgG anti-PC decreased after 1 year, but reached similar levels as mothers´ after 2 years while IgG anti-MDA reached similar levels as mothers´ already after one year. Proteomics peptide sequencing analysis indicates large peptide sequence variation without specific clone expression during early stage of life compared to the adult stage for which specific peptide sequences dominated.

Conclusion:

IgM anti-PC levels develop much slower than anti-MDA and are still relatively low at 2 years. We hypothesize that anti-PC is developed by a combination of pre-programming and exposure to the external world, where infectious agents may play a role. For anti-MDA pre-programming is likely to play a major role and at an earlier stage than for anti-PC.

References:

[1]Frostegard J. Immunity, atherosclerosis and cardiovascular disease.BMC Med. 2013;11:117.

[2]Rahman M, Sing S, Golabkesh Z, Fiskesund R, Gustafsson T, Jogestrand T, Frostegard AG, Hafstrom I, Liu A and Frostegard J. IgM antibodies against malondialdehyde and phosphorylcholine are together strong protection markers for atherosclerosis in systemic lupus erythematosus: Regulation and underlying mechanisms.Clin Immunol. 2016;166-167:27-37.

[3]Sun J, Lundstrom SL, Zhang B, Zubarev RA, Steuer J, Gillgren P, Rahman M, Ajeganova S, Liu A and Frostegard J. IgM antibodies against phosphorylcholine promote polarization of T regulatory cells from patients with atherosclerotic plaques, systemic lupus erythematosus and healthy donors.Atherosclerosis. 2018;268:36-48.

Disclosure of Interests:

Divya Thiagarajan: None declared, Susanna Lundström: None declared, Göran Pershagen: None declared, Catharina Almqvist Malmros: None declared, Ellika Andolf: None declared, Anna Hedman: None declared, Oscar Berg: None declared, Nina Oparina: None declared, Johan Frostegård Grant/research support from: Unconditional competitive grant from Amgen, related only to PCSK9, not the topic of this abstract

Rapid breakthrough of 131I in an in vitro human epidermis model

Skin contamination with radionuclides may cause local radiation damage, but also systemic distribution if the nuclides penetrate the epidermal membrane. Detailed information of the skin absorption of radionuclides is of importance for e.g. dose estimations and development of decontamination strategies. In the present study, penetration of ¹³¹I through human epidermis was studied using an in vitro flow through diffusion chamber. Epidermis was exposed to a Na¹³¹I-solution, used in nuclear medicine, and the potential concentration-dependency of skin penetration was examined by including two concentrations of non-radioactive NaI. Penetration of ¹³¹I occurred after a few minutes of exposure and steady state penetration rate was obtained after about 50-70min independently of the iodine concentration and receptor solution used. The two receptor solutions evaluated; phosphate buffered saline solution and an ethanol and water-mixture (1:1), resulted in significantly higher penetration rate of ¹³¹I using the ethanol and water-mixture. The penetration of iodine was calculated to be concentration-dependent independently of the receptor solution utilized. In addition, radioactive iodine did not accumulate in epidermis in the in vitro-model used. In conclusion, the present study provides detailed information on the rapid iodine penetration at the early phase of radionuclide exposure, defined as the first 30min of the experiment, and is clearly suitable for decontamination studies. In addition, methodological aspects, e.g. impact of the receptor solution, should carefully be considered in studies of radionuclide skin penetration using in vitro-techniques.

Effects of intravenous exenatide in type 2 diabetic patients with congestive heart failure: a double-blind, randomised controlled clinical trial of efficacy and safety

AIMS/HYPOTHESIS

The aim of this study was to determine whether exenatide improves haemodynamic function in patients with type 2 diabetes with congestive heart failure (CHF).

METHODS

The main eligibility criteria for inclusion were: male/female (18-80 years) with type 2 diabetes and CHF (ejection fraction ≤ 35%, and New York Heart Association functional class III or IV). Out of 237 patients screened, 20 male type 2 diabetic patients participated in this crossover trial design and were allocated (sequentially numbered) to i.v. infusions during two consecutive days with (1) exenatide (0.12 pmol/kg/min); and (2) placebo for 6 h followed by a washout period for 18 h, at Stockholm South Hospital, Sweden. Patients and researchers were blinded to the assignment. Cardiac haemodynamic variables were determined by right heart catheterisation. The primary endpoint was defined as an increase in cardiac index (CI) or a decrease in pulmonary capillary wedge pressure (PCWP) of ≥ 20%. Secondary endpoints were tolerability and safety of exenatide infusion.

RESULTS

CI increased at 3 and 6 h by 0.4 ± 0.1 (23%) and 0.33 ± 0.1 (17%) l min(-1) m(-2), during exenatide infusion vs -0.02 ± 0.1 (-1%) and -0.08 ± 0.1 (-5%) l min(-1) m(-2) during placebo (p = 0.003); and heart rate (HR) increased at 1, 3 and 6 h by 8 ± 3 (11%), 15 ± 4 (21%) and 21 ± 5 (29%) beats per min (bpm), during exenatide infusion vs -1 ± 2 (-2%), 1 ± 1 (2%) and 6 ± 2 (8%) bpm, during placebo (p = 0.006); and PCWP decreased at 1, 3 and 6 h by -1.3 ± 0.8 (-8%), -1.2 ± 1 (-8%) and -2.2 ± 0.9 (-15%) mmHg, during exenatide infusion vs 0.3 ± 0.5 (2%), 1 ± 0.6 (6%) and 1.4 ± 0.7 (8%) mmHg, during placebo (p = 0.001). No serious adverse event was observed. Adverse events were reported in nine patients (six, nausea; two, increased HR; one, increased systolic blood pressure).

CONCLUSIONS/INTERPRETATION

Infusion of exenatide in male type 2 diabetic patients with CHF increased the CI as a result of chronotropy, with concomitant favourable effects on PCWP and reasonable tolerability of the drug. The clinical implications of using exenatide in patients with CHF are still not clear and further studies are warranted.

TRIAL REGISTRATION

www.isrctn.org/ISRCTN47533126

Inducibility of life-threatening ventricular arrhythmias is related to maximum left ventricular thickness and clinical markers of sudden cardiac death in patients with hypertrophic cardiomyopathy attributable to the Asp175Asn mutation in the alpha-tropomyosin gene

We investigated inducibility of life-threatening arrhythmias with programmed ventricular stimulation (PVS) in relation to clinical markers of sudden cardiac death (SCD) in subjects with hypertrophic cardiomyopathy (HCM) attributable to the Asp175Asn mutation in the alpha-tropomyosin gene (TPM1-Asp175Asn). PVS was performed with up to three extrastimuli and distribution of markers of SCD was evaluated in 21 adult subjects with the TPM1-Asp175Asn. Sustained polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) was induced in seven of 21 subjects (33%). Inducible subjects had more severe left ventricular hypertrophy (LVH) and an increased number of markers of SCD (family history of SCD, syncope or presyncope, fall in systolic blood pressure (BP) during exercise, documented non-sustained VT (NSVT), and marked LVH) compared to non-inducible subjects (IVS 2.4 +/- 0.3 cm vs. 1.6 +/- 0.5 cm, P < 0.001; and two to three vs. one to two markers of SCD, P = 0.007, respectively). In conclusion, in HCM attributable to the Asp175Asn mutation in the alpha-tropomyosin gene, life-threatening arrhythmias were induced in one third of the patients. Inducibility was associated with the maximum left ventricular (LV) thickness and the number of markers of SCD, suggesting that in HCM patients with an identical causative mutation, susceptibility to ventricular arrhythmias is related to the cardiomyopathic phenotype.

Cardiac arrest after interscalene brachial plexus block with ropivacaine and lidocaine

Serious adverse reactions to ropivacaine and lidocaine are rare. In this report, we describe a case of sudden cardiac arrest after an interscalene brachial plexus block with a mixture of 150 mg of ropivacaine and 360 mg of lidocaine in a previously healthy, 34-year-old, 97-kg man. Severe hypotension occurred after successful resuscitation, necessitating an infusion of epinephrine. The patient developed pulmonary oedema, and was mechanically ventilated for 22 h. He eventually made a good recovery. We conclude that although ropivacaine and lidocaine are often considered relatively safe local anesthetics, serious cardiovascular complications can occur after the use of these drugs.

Prediction of atrial fibrillation after coronary artery bypass grafting by measuring atrial peptide levels and preoperative atrial dimensions

OBJECTIVE

We prospectively tested the hypothesis that atrial enlargement and increased level of atrial natriuretic peptide, N-terminal atrial natriuretic peptide and brain natriuretic peptide would predict atrial fibrillation after coronary artery bypass grafting.

METHODS

Eighty-eight elective coronary artery bypass grafting patients had preoperative echocardiographic assessment. The level of atrial natriuretic peptide, N-terminal atrial natriuretic peptide and brain natriuretic peptide were measured preoperatively. Patients were ECG- monitored during the whole hospital stay.

RESULTS

Thirty one (35.2%) patients had postoperative atrial fibrillation. In univariate analysis increased age (P=0.003), enlargement of left and right atria (P=0.002 and P=0.004, respectively) and increased level of preoperative atrial natriuretic peptide and N-terminal atrial natriuretic peptide (P=0.016 and P=0.03, respectively) were associated with postoperative atrial fibrillation. There was correlation between the age and level of N-terminal atrial natriuretic peptide (r=0.45 and P<0.001). In multivariate analysis only age and the left atrial enlargement were independent predictors of postoperative atrial fibrillation (P=0.02 and P=0.01).

CONCLUSION

Left atrial enlargement was independent predictor for postoperative atrial fibrillation. However, atrial peptides were associated with age and did not independently predict postoperative atrial fibrillation. In addition, the wide variation of the peptide levels renders the implementation of this measure in clinical practice superfluous.

Muscle morphology, self-reported physical activity and insulin resistance syndrome

In a population-based sample of 475 men the associations between muscle morphology, self-reported physical activity (PA) and insulin resistance (IR) syndrome were investigated. Also, we studied to what degree muscle morphology contributes to the association between PA and IR syndrome. Muscle morphology and the components of IR syndrome were compared in four groups categorized according to self-reported habitual PA data. We found a significantly higher percentage of type I fibres, fibre area and number of capillaries around the fibres and a lower proportion of type IIB fibres with higher level of PA. The relative distribution of type I fibres and capillarization were positively related to high density lipoprotein (HDL) cholesterol and negatively to serum triglycerides (TG) and plasminogen activator inhibitor-1 (PAI-1) activity. The percentage of type IIB fibres was were inversely related to HDL cholesterol and positively to serum TG, PAI-1 activity and resting heart rate. Insulin sensitivity was positively and independently related to PA level (P < 0.001). Regression analysis including all relevant variables regarding insulin sensitivity indicated that the significant explanatory variables left in the equation were body mass index (BMI), glucose intolerance, PAI-1 activity, serum free fatty acid concentration, proportion of type IIB fibres, HDL cholesterol level, drug treatment, PA level, and waist-to-hip ratio, which together explained 55% of the variation in the insulin sensitivity index. In conclusion, both fibre type distribution and muscle capillary density might contribute to the beneficial effect of PA on IR syndrome.

Insulin-mediated changes in leg blood flow are coupled to capillary density in skeletal muscle in healthy 70-year-old men

The aim of this study was to investigate to what degree the capillarization in the skeletal muscle explains the leg blood flow (LBF) changes during hyperinsulinaemia. Fifteen normotensive men from a population-based cohort of 70-year-old men in Uppsala, Sweden, were investigated. Their metabolic status (oral glucose tolerance test and euglycemic, hyperinsulinaemic clamp test results), serum lipid profile, muscle fiber distribution (myosin adenosine triphosphatase staining), and capillary supply (amylase-periodic acid-Schiff method) was evaluated. Doppler ultrasound was used before and after the clamp test to detect insulin-induced changes in LBF. Physiologic hyperinsulinemia (serum insulin, 107 mU/L) caused a moderate increase in LBF (15% +/- 11%; P =.07). Change in LBF was closely related to capillary density (r =.66; P <.01) independent of obesity, smoking and level of physical activity. An association was observed between LBF and serum free fatty acid (FFA) concentrations (r = -.57; P <.05). In multiple regression analysis, capillary density and serum FFA level together explained 71% of the variation in insulin-mediated LBF changes. Capillary rarefaction and elevated serum FFA values were associated with a vasoconstrictive effect of insulin. In conclusion, capillarization in skeletal muscle and serum FFA concentration seem to be determinants of endothelial function.

Diurnal variations of the dominant cycle length of chronic atrial fibrillation

High-resolution digital Holter recording was carried out in 21 patients (15 men, 64 +/- 12 yr) with chronic atrial fibrillation. Dominating atrial cycle length (DACL) was derived by frequency domain analysis of QRST-reduced electrocardiograms. Daytime mean DACL was 150 +/- 17 ms, and nighttime mean was 157 +/- 22 ms (P = 0. 0002). Diurnal fluctuation in DACL differed among patients: it tended to be virtually absent in those with a short mean DACL, but in those with longer DACL the night-day difference was as much as 23 ms (R = 0.72, P < 0.001, correlation of mean DACL to night-day difference). Mean DACL also correlated with ventricular cycle length (R = 0.40, P < 0.001), particularly at night (r = 0.49). The shorter cycle lengths found in this study during the day are consistent with sympathetic and/or other physiological modulation, but since increased vagal tone shortens atrial refractoriness in most models, parasympathetic influences are not likely to play a major role. Alternatively, atrial effective refractory period may not be the sole determinant of atrial cycle length during atrial fibrillation.

Fatty acid profile of skeletal muscle phospholipids in trained and untrained young men

Endurance trained (n = 14) and untrained young men (n = 15) were compared regarding the fatty acid profile of the vastus lateralis muscle after 8 wk on diets with a similar fatty acid composition. The skeletal muscle phospholipids in the trained group contained lower proportions of palmitic acid (16:0) (-12.4%, P < 0.001) and di-homo-gamma-linolenic acid [20:3(n-6)] (-15.3%, P = 0.018), a lower n-6-to-n-3 ratio (-42.0%, P = 0.015), higher proportions of stearic acid (18:0) (+9.8%, P = 0.004) and sum of n-3 polyunsaturated fatty acids (+33.8%, P = 0.009), and a higher ratio between 20:4(n-6) to 20:3(n-6) (+18.4%, P = 0.006) compared with those in the untrained group. The group differences in 16:0, 20:3(n-6), 18:0/16:0, and 20:4(n-6)/20:3(n-6) were independent of fiber-type distribution. The trained group also showed a lower proportion of 16:0 (-7.9%, P < 0.001) in skeletal muscle triglycerides irrespective of fiber type. In conclusion, the fatty acid profile of the skeletal muscle differed between trained and untrained individuals, although the dietary fatty acid composition was similar. This difference was not explained by different fiber-type distribution alone but appears to be a direct consequence of changes in fatty acid metabolism due to the higher level of physical activity.

Relationships between muscle morphology and insulin sensitivity are improved after adjustment for intra-individual variability in 70-year-old men

The purpose of this investigation was to examine to what extent variability in the muscle morphology and insulin sensitivity influence the correlation between them. Reproducibility of muscle characteristics was estimated in duplicate biopsies from the same thigh of 23 subjects from a cohort of 70-year-old men. The coefficient of variation (CV) for different characteristics of muscle morphology was between 11 and 42% in duplicate biopsies. Coefficient of variation for markers of insulin sensitivity ranged between 12 and 39%. The variability reflected by intra-class correlation ranged from 0.23 to 0.60 for muscle morphology and from 0.68 to 0.96 for estimates of insulin sensitivity. The correlation analysis between muscle morphology and insulin resistance was performed in a sample of 515 men from the cohort, correlation coefficients were calculated with (rtrue) and without (r) adjustment for intra-individual variation. Insulin sensitivity showed a positive relationship with percentage of type I fibres (rtrue=0.33, r=0.21; P < 0.0001) and capillary density (rtrue=0.43, r=0.21; P < 0. 0001) and negative correlations with percentage of type IIB fibres (rtrue=-0.35, r=-0.24; P < 0.0001). Capillary density was inversely correlated to insulin. Thus, an obvious improvement of the correlation was seen after correcting intra-individual variation. In conclusion, owing to the low degree of reproducibility of muscle morphology variables and insulin sensitivity, implying a noticeable underestimation of correlations, the r-values should be adjusted for within-subject variation in order to demonstrate a more accurate estimate of the strength of the relationships studied.

Alterations in skeletal muscle morphology in glucose-tolerant elderly hypertensive men: relationship to development of hypertension and heart rate

OBJECTIVE

To compare the muscle morphology in hypertensive subjects with that in controls and to test the hypothesis of a relation between heart rate, development of hypertension and muscle morphology that is independent of glucose intolerance.

PATIENTS AND METHODS

We studied 43 glucose-tolerant, untreated hypertensive subjects and 113 healthy controls in a longitudinal cohort of 70-year-old men. Metabolic status (oral glucose tolerance test and euglycemic, hyperinsulinaemic clamp test), muscle fibre distribution (myosin ATPase staining) and capillary supply (amylase-PAS method) were evaluated. Blood pressure and heart rate data were available from both ages 50 and 70 years.

RESULTS

Hypertensive subjects had a significantly smaller mean number of capillaries per fibre than controls (1.53 versus 1.64; P = 0.04). In hypertensive subjects, the proportions of type I and type II fibres were correlated to mean arterial pressure (r = -0.56 and r= 0.52, respectively, P < 0.05 for both). The increase in mean arterial pressure over 20 years was closely correlated to capillary density in mm2 (r= -0.62; P< 0.0001). Capillary supply was inversely related to resting heart rate both at ages 50 and 70 years.

CONCLUSIONS

Skeletal muscle of glucose tolerant hypertensive subjects showed a lower capillary supply than that of controls. This capillary rarefaction was correlated to increase in mean arterial pressure over two decades and to supine heart rate. This is compatible with the suggestion that higher sympathetic drive might generate structural alterations in muscle capillarization.

Epidemiological and clinical studies on insulin resistance and diabetes

In Uppsala, extensive epidemiological and clinical studies on insulin resistance and diabetes have been ongoing for the past 30 years. A prospective cohort study of men born 1920-24, living in Uppsala County, was initiated during 1969-74 (the Uppsala Longitudinal Study of Adult Men, ULSAM). Risk factors for cardiovascular disease were examined in 2,322 men, and re-examinations have been performed every 10 years. At the first follow-up, when the men were 60 years old, insulin resistance was found to be a risk factor for development of hypertension and diabetes. In addition, treatment with antihypertensive medication was an independent risk factor for development of diabetes. These findings resulted in a series of clinical studies on metabolic effects of antihypertensive agents. At the second follow-up, when the men were 70 years old, the development of hypertension and diabetes was once again in focus, but at this time, cross-sectional and prospective studies of other cardiovascular determinants, such as circadian blood pressure pattern, left ventricular geometry and function, muscle morphology, ion status, fibrinolysis and cognitive function, were also performed. The cohort has furthermore been linked to the Swedish census and hospital discharge and cause of death registries, it has been used for studies on relationships between birth weight and cardiovascular disease, and genetic analyses have been performed, taking advantage of the long observation time obtained in this cohort. The cohort is currently being re-examined for the third time, and will hopefully continue to provide valuable information on the epidemiology of diabetes and cardiovascular disease in the future.

Cardioversion of atrial fibrillation and its effect on right ventricular function as assessed by tricuspid annular motion

In patients with atrial fibrillation, the reduced right ventricular function determined by tricuspid annular motion before cardioversion returns to normal 1 month after successful cardioversion to sinus rhythm. The simplicity of recording the tricuspid annular motion provides an easy opportunity to assess right ventricular function following electroconversion of atrial fibrillation to sinus rhythm.

Effect of renal disease and hemodialysis on foscarnet pharmacokinetics and dosing recommendations

BACKGROUND

Foscarnet is an antiviral agent commonly used for managing patients with cytomegalovirus infection. Despite its clinical usefulness, foscarnet is associated with substantial adverse effects including nephrotoxicity. Moreover, foscarnet is primarily eliminated unchanged through the kidneys, thus requiring aggressive dose adjustment during kidney failure. To develop specific dosage guidelines, information on the disposition of this compound in patients with varying degrees of renal function and those requiring dialysis is essential.

DESIGN

Twenty-six subjects were enrolled in this study and divided into five groups depending on their degree of renal dysfunction. Group 1 included subjects with normal renal function; group 5 included subjects requiring maintenance hemodialysis. Nondialysis study subjects received a single 60-mg/kg intravenous dose of foscarnet whereas hemodialysis subjects received two intravenous doses, separated by 1 week, to compare the effects of conventional and high-flux dialysis methods.

RESULTS

Mean plasma clearance in control subjects averaged 2.1+/-0.7 ml/minute/kg and declined proportionally with changing renal function as indicated by the regression equation: Clp (ml/minute/kg) = 1.48 [CrCl (ml/minute/kg)]-0.08 (r2 = 0.82). Mean half-life averaged 1.9+/-0.1 hours in normal subjects and increased to a mean of 25+/-19 hours in study subjects with severe impairment not on dialysis. Foscarnet dialysis clearance (based on dialysate recovery) averaged 183 ml/minute with conventional dialysis methods and 253 ml/minute during high-flux procedures, which resulted in removal of 37% and 38% of a dose for the two methods, respectively.

CONCLUSIONS

These data indicate that substantial dosage adjustments must be made in renal failure patients. Therefore, a patient-specific dosage nomogram has been developed.

Stereoselective inhibition by the diastereomers quinidine and quinine of uptake of cardiac glycosides into isolated rat hepatocytes

The pharmacokinetic interaction between quinidine and digoxin in patients is well-known, in general requiring a dose reduction of digoxin in patients concomitantly treated with quinidine. Quinine, the diastereomer of quinidine, has not been as extensively studied in this respect. In addition to an interaction with the renal clearance of digoxin by quinidine, both diastereomers have been reported to inhibit the biliary clearance of digoxin in man. To further investigate the mechanisms of these hepatobiliary transport interactions at the cellular level, we compared the effects of quinidine and quinine, as well as of the calcium antagonist verapamil, on the uptake of digoxin and ouabain in isolated rat hepatocytes. Initial uptake rates of digoxin and ouabain were determined in the presence of various concentrations of quinine and quinidine. A concentration dependent inhibition of the cellular uptake of both cardiac glycosides by quinine and quinidine was found, quinine being a more potent inhibitor than quinidine. Our results indicate a stereoselective inhibition of the hepatocellular uptake by the two diastereomers quinidine and quinine, the latter being about equipotent to verapamil. This unequal inhibitory potency of the two basic drugs was detected earlier in oocyte studies with the cloned organic cation transporter OCT1.

The stereoisomers quinine and quinidine exhibit a marked stereoselectivity in the inhibition of hepatobiliary transport of cardiac glycosides

BACKGROUND/AIMS

Certain basic (cationic) drugs are known to interact with the hepatic transport, and renal and/or biliary clearance of cardiac glycosides. The mechanisms behind these interactions are not fully understood. In the present study our aim was to investigate the effects of the two diastereomers, quinidine and quinine, as well as the calcium antagonist verapamil, on the hepatobiliary elimination of digoxin and ouabain in the isolated perfused rat liver.

METHODS

Livers from male, fasting Wistar rats were perfused by recirculation of Krebs-Henseleit bicarbonate buffer supplemented with 1% BSA. Disposition of digoxin or ouabain was studied at an initial perfusion medium concentration (Ci) of 100 or 10 nmol/l for digoxin and a Ci of 30 micromol/l for ouabain. The Ci of quinine, quinidine or verapamil was 50 micromol/l. Concentrations of the drugs in perfusion medium and bile were followed up to 2 h.

RESULTS

A marked reduction in the initial medium disappearance rate of digoxin and ouabain by quinine was found, whereas quinidine did not affect the hepatic disposition of the cardiac glycosides. The stereoselective inhibition of digoxin and ouabain clearance by quinine, and not by quinidine, was shown to be due to an effect on the hepatic uptake level rather than on the metabolic conversion and/or the biliary excretion steps. An allosteric type of inhibition by the basic drugs, exerted from the inside of the cells, is inferred. This interaction may occur at the sinusoidal plasma membrane on the level of multi-specific carrier proteins for cardiac glycosides and cationic drugs, as cloned recently by various groups.

CONCLUSIONS

A marked stereoselective difference was found in the effect of the stereoisomers quinidine and quinine on the hepatic uptake of digoxin and ouabain, quinine being the potent inhibitor.

Prevalence and treatment of chronic idiopathic thrombocytopenic purpura of childhood in Sweden

The frequency and treatment of children with chronic idiopathic thrombocytopenic purpura in Sweden were characterized using a national enquiry based on a questionnaire. Seventy-five children diagnosed as having chronic idiopathic thrombocytopenic purpura on 1 September 1993 were identified. The prevalence in children between 0.5 and 15.5 years of age was calculated to be 4.6/100,000. The median age at the time of diagnosis was 5 years and the male/female ratio was 1:1.2. Almost half of the patients (43%) were not treated at all during the disease. Steroids (43%) and intravenous immunoglobulin (25%) were most commonly used. Only two children were splenectomized.

Comparison of pharmacokinetics and dynamics of two dosage regimens of foscarnet in AIDS patients with Cytomegalovirus retinitis

OBJECTIVE

To compare the pharmacokinetics of foscarnet administered as an infusion twice daily (BID) or thrice daily (TID), and to compare the effects on the electrolyte balance, cardiac and renal functions over a 3-week induction treatment of Cytomegalovirus (CMV) retinitis.

METHODS

Pharmacokinetics/dynamics of foscarnet were investigated on treatment days 1, 14 and 21. Twelve AIDS patients with CMV retinitis completed the investigation period. Concentrations of foscarnet and electrolytes were assayed by high-performance liquid chromatography (HPLC) and by an ion-selective analyser, respectively.

RESULTS

The pharmacokinetics of the two regimens were essentially similar. Foscarnet plasma and creatinine clearances were 2.0 and 1.6 ml.min-1.kg-1, respectively, in the BID group at steady state (day 21). In the TID group the corresponding values were 1.8 and 1.7 ml.min-1.kg-1, respectively. In both regimens the elimination half-life of foscarnet was 2-3 h. Ionized calcium concentrations were transiently decreased and strongly inversely correlated to foscarnet plasma concentrations in both regimens with no significant differences between groups. A trend towards prolongation of the QTc interval was seen when data from both treatments were analysed together.

CONCLUSION

Our data suggest comparable pharmacokinetics of foscarnet after intermittent administration BID or TID during a 3-week induction period.

Renal elimination of ceftazidime during pregnancy

OBJECTIVE

Our purpose was to study the pharmacokinetics of ceftazidime at different stages of pregnancy and in the nonpregnant state to determine whether glomerular filtration rate is altered and whether tubular secretions occurs.

STUDY DESIGN

Twelve pregnant women with asymptomatic bacteruria were given a bolus dose of 400 mg of ceftazidime followed by a constant infusion for 4 hours. Inulin was infused simultaneously to determine glomerular filtration rate. Blood samples were drawn every 30 minutes. Urine was collected immediately after the bolus dose and then every hour. The same study procedure was then repeated twice: 2 weeks before the expected delivery and after termination of breast-feeding.

RESULTS

At term clearance values were raised by 50% to 100% compared with the values found in the postpartum period. At all observation points a close correlation between inulin and ceftazidime clearance values were found.

CONCLUSION

The results strongly indicate that ceftazidime is excreted exclusively by glomerular filtration with no tubular reabsorption. During pregnancy the excretion pattern is unaltered, but renal elimination is increased.

Dose proportional absorption of 25-150 mg atenolol

We investigated the dose proportionality after the intake of oral atenolol 25, 50, 100 and 150 mg. Standard tablets were taken by 8 healthy volunteers in randomised order of doses. The area under the curve divided by dose did not differ between the doses, indicating that the absorption of this hydrophilic compound, with known incomplete bioavailability, was constant over the range tested.

Digoxin-interactions in man: spironolactone reduces renal but not biliary digoxin clearance

The possibility of an inhibitory effect of spironolactone on the biliary clearance of digoxin has been investigated in 6 healthy subjects. Plasma clearance and the renal and biliary clearance of digoxin were determined twice at steady state (digoxin 0.5 to 1 mg.d-1 p.o. for 6 days), alone or in combination with spironolactone 200 mg daily, after an intravenous dose of digoxin (0.7 x oral dose) on Day 7. Plasma and urine were collected for 48 h. Biliary clearance of digoxin was determined on Day 8 by a duodenal perfusion technique. During spironolactone treatment plasma digoxin clearance tended to be lower (255 vs 224 ml/min; P = 0.057) and renal clearance significantly lower (166 vs 144 ml/min), while the biliary clearance of digoxin remained unchanged (106 vs 103 ml/min). Thus, spironolactone reduced the renal clearance of digoxin by an average of 13%, without affecting its biliary clearance.

Inhibition by basic drugs of digoxin secretion into human bile

Bile samples from previous interaction studies in man were re-analysed by a combined HPLC/radioimmunoassay method. Quinidine, quinine and verapamil but not probenecid or spironolactone were found to inhibit the biliary secretion of unchanged digoxin.

No effect of probenecid on the renal and biliary clearances of digoxin in man

1. The cardiac glycoside digoxin is subject to a number of pharmacokinetic interactions. This study concerns the influence of the anionic transport inhibitor probenecid on the steady-state kinetics of digoxin. 2. Six healthy young men were enrolled in the study. After an administration period of 6 days with digoxin only (0.5 to 1 mg p.o. day-1) or digoxin in combination with probenecid (2 g p.o. day-1; 8 days), digoxin was administered intravenously (0.7 oral dose) on day 7. Plasma and urine samples were taken over 48 h. The biliary clearance of digoxin was measured during day 8 by a duodenal perfusion technique. 3. Probenecid did not affect the plasma clearance (mean +/- s.d.: 255 +/- 80 vs 266 +/- 40 ml min-1), renal clearance (166 +/- 17 vs 155 +/- 10 ml min-1), biliary clearance (106 +/- 40 vs 111 +/- 50 ml min-1), elimination half-life (34.4 vs 35.2 h) or volume of distribution (538 +/- 241 vs 566 +/- 60 l) of digoxin. 4. Our results suggest that different systems exist in man for the renal and biliary secretion of probenecid and digoxin.

Hemodynamics and exercise capacity during pacemaker stimulation

This review summarizes the present knowledge concerning the hemodynamic and myocardial effects of various pacing modalities with special reference to the importance of heart rate variability and atrioventricular synchronization. An adequate increase in heart rate, irrespective of atrioventricular synchronization, seems to be the most important denominator for cardiac output and exercise tolerance. Atrioventricular synchronization will add some hemodynamic benefit, which is most pronounced at rest. The importance of a rate-adaptive atrioventricular delay and a normalized ventricular activation sequence remains, however, to be fully established. Myocardial oxygen consumption does not differ during fixed rate ventricular pacing, atrial synchronous or non-synchronous rate-adaptive ventricular pacing, neither at rest nor during exercise, despite a higher cardiac output during the rate-adaptive modes. This indicates a more "economic" cardiac work with rate-adaptive pacing. Fixed rate ventricular pacing, on the other hand, may have negative long-term effects on myocardial function due to an increased cardiac sympathetic activity compared with rate-adaptive ventricular pacing, in particular during exercise. It is concluded that the majority of pacemaker-dependent patients will benefit from restored rate variability, with the atrial electrogram still being the most appropriate trigger for rate-adaptive ventricular pacing. When the atrial signal cannot be used or when it is unreliable, however, other rate-triggering signals can be used with comparable results regarding hemodynamics and exercise tolerance.

Digoxin-verapamil interaction: reduction of biliary but not renal digoxin clearance in humans

The interaction between digoxin and verapamil was studied in six patients (mean age +/- SD, 61 +/- 5 years) with chronic atrial fibrillation. The effects of adding verapamil (240 mg/day) on steady-state plasma concentrations and renal and biliary clearances of digoxin were studied in a crossover manner. The biliary clearance of digoxin was determined by a duodenal perfusion technique. Verapamil induced a 44% increase in steady-state plasma concentrations of digoxin, from 0.80 +/- 0.24 to 1.15 +/- 0.40 nmol/L (p less than 0.01). The biliary clearance of digoxin decreased by 43%, from 187 +/- 89 to 101 +/- 55 ml/min (p less than 0.05), in the presence of verapamil, whereas the renal clearance was unaffected (153 +/- 31 versus 173 +/- 51 ml/min; difference not significant). Our results indicate that the main inhibitory effect of verapamil on digoxin elimination is on the biliary route.

Decreased renal clearance of sodium in cystic fibrosis

In 10 patients with cystic fibrosis (CF) and 10 controls of similar age quantitative segmental handling of sodium was estimated by lithium clearance. In the CF group, there was a tendency for an increased glomerular filtration rate (GFR) and increased absolute proximal sodium reabsorption. The fractional distal sodium reabsorption was significantly (p = 0.015) increased and sodium clearance was significantly (p less than 0.01) decreased in CF.

Plasma and renal clearance of iohexol--a study on the reproducibility of a method for the glomerular filtration rate

The reproducibility of iohexol clearance as a determination of the glomerular filtration rate was assessed in 12 healthy subjects during triplicate constant-rate infusions. Renal and plasma clearance of iohexol demonstrated a total within-subject variation (CV) ranging between 0% and 16%. The inter-individual variation in renal clearance was about 10%, the clearance values being (mean +/- SD) 116 +/- 10, 117 +/- 9 and 110 +/- 12 ml/min 1.73 m2 in the three experiments and corresponding figures for the plasma clearance were 120 +/- 17, 118 +/- 12 and 112 +/- 14 ml/min 1.73 m2. The renal clearance (CLR) and the plasma clearance (CL) showed good correlation (regression equation CL = 11.80 + 0.93 CLR, rs = 0.67). The method is simple and reproducible; thus, it is suitable for both clinical examinations and research.

Effects of mental and physical stress on central haemodynamics and cardiac sympathetic nerve activity during QT interval-sensing rate-responsive and fixed rate ventricular inhibited pacing

The effects of mental stress and dynamic exercise on central haemodynamic variables and cardiac sympathetic nerve activity were studied in 15 patients during both fixed rate ventricular-inhibited (VVI) and QT interval-sensing rate-responsive (TX) pacing. Haemodynamic measurements were made at rest, during a mental stress test and during supine exercise at 30 W. Cardiac sympathetic nerve activity was assessed by measuring the arterial and coronary sinus plasma concentrations of noradrenaline (NA) and adrenaline (ADR), the NA kinetics in arterial plasma (radiotracer infusion) and the overflow of NA into the coronary sinus. During exercise the paced ventricular rate increased by 47% with TX. TX provided a higher cardiac output than VVI despite a similar myocardial oxygen consumption and a lower level of cardiac sympathetic activity. Cardiac NA overflow based on 3H-NA extraction over the heart increased from 182 to 1046 pmol min-1 in the VVI mode (P less than 0.01) and from 178 to 793 pmol min-1 in the TX mode (P less than 0.001). The difference in cardiac NA overflow in response to exercise (P less than 0.05 by ANOVA) was not reflected in similar differences in arterial NA concentrations or spill over rates. During mental stress the ventricular rate increased in 12/14 patients. Noradrenaline overflow increased similarly in the two modes. Changes in cardiac NA overflow during mental stress and exercise were correlated with increases in TX pacing rate. This study confirms that both mental and physical stress cause significant changes in cardiac sympathetic nerve activity and central haemodynamic variables, and that the TX pacemaker responds by increasing its pacing rate in a physiological manner.

Increased renal clearance of cefsulodin due to higher glomerular filtration rate in cystic fibrosis

The steady-state renal clearance of cefsulodin was studied in 6 patients with cystic fibrosis and 8 healthy controls. The drug was administered by constant rate infusion to obtain 2 values of plasma concentration, 2 and 30 mg/L. As an estimate of the glomerular filtration rate, the renal clearance of inulin was measured simultaneously. The results showed the figures for inulin clearance to be approximately 30% higher in cystic fibrosis patients than in healthy controls at both concentrations, and a corresponding increase in the renal clearance of cefsulodin was seen in patients over controls. The ratio between the renal clearances of the 2 substances was on average 0.9 in both groups. The correlation found between the 2 renal clearances (r = 0.75; p less than 0.001) indicates that glomerular filtration rate has considerable influence on the renal elimination of cefsulodin. This finding emphasises the importance of glomerular filtration rate for the renal clearance of drugs in cystic fibrosis.

Interactions in the renal and biliary elimination of digoxin: stereoselective difference between quinine and quinidine

The interactions between digoxin and quinine and quinidine that affect the renal and biliary clearances of digoxin were investigated in eight healthy subjects. Digoxin (0.5 to 0.75 mg/day) was given alone and with concomitant administration of quinine (750 mg/day) to reach a steady-state level. In four of the subjects, the study was repeated by administration of equimolar doses of the diastereoisomer quinidine together with digoxin, enabling a within-subject comparison of the effects of the two isomers on digoxin clearance. The biliary excretion of digoxin was studied by use of a modified duodenal marker perfusion technique. A marked reduction was found in the steady-state biliary clearance of digoxin from control value 134 +/- 57 ml/min (mean +/- SD) to 87 +/- 39 ml/min during treatment with quinine (p less than 0.05) and from 95 +/- 24 to 55 +/- 27 ml/min during treatment with quinidine (p less than 0.01; n = 4). Quinidine reduced the renal clearance of digoxin (155 +/- 26 versus 110 +/- 21 ml/min) (p less than 0.05; n = 4), whereas quinine had no such effect (177 +/- 40 versus 185 +/- 53 ml/min; not significant). These findings explain the difference in magnitude between quinidine and quinine in regard to the interaction with digoxin and imply a different degree of stereoselectivity for these isomers in the renal and biliary secretory systems of digoxin.

Long-term follow-up of patients treated with the QT interval sensing rate-responsive pacemaker

Thirty-seven patients (mean age 70 years) with QT-interval sensing (TX) rate-responsive pacemakers were followed for a mean of 27 months. This pacemaker measures the QT interval of the paced beat and, if the QT shortens, the pacing rate increases according to a programmed relationship, the 'slope'. With TX pacing the heart rate was 56% and the exercise tolerance 15% higher than with fixed-rate ventricular-inhibited (VVI) pacing during exercise. Holter ECG monitoring showed a physiological rate variability. Six patients (16%) have died during follow-up, and programming to the VVI mode was necessary in six patients (16%). The remaining patients were alive with a subjectively adequate TX function at the end of follow-up. Including the five patients who were on TX pacing at the time of death, satisfactory TX pacing was obtained in 84% of the patients. Although the TX pacemaker has been reliable and provides an adequate rate response during exercise, complaints of worsening angina pectoris and the somewhat complicated programming of the device are problems with the current models.

QT sensing rate responsive pacing and myocardial infarction: a case report

A 65-year-old man, treated with the QT sensing rate responsive pacemaker required to manage high degree AV block, sustained a transmural inferior wall myocardial infarction 6 months after the pacemaker implant. The rate response of the pacemaker during the acute phase of the infarction was physiological as evidenced by increased pacing rate during pain and with the gradual decrease in rate during the first postinfarction days. The underlying mechanisms are discussed.

QT sensing rate responsive pacing compared to fixed rate ventricular inhibited pacing: a controlled clinical study

Eighteen patients, five women and 13 men, (mean age 70 +/- S.E.M. 2 years) treated with QT sensing rate responsive pacemakers due to symptomatic high degree AV block took part in a double-blind study, comparing the rate responsive (TX) mode with fixed rate ventricular inhibited (VVI) pacing. The pacemaker was blindly programmed to either mode in a cross-over design. During the 1 month period a daily diary of symptoms (chest pain, vertigo, dyspnea, and palpitations) was kept. At the end of each period, a mental stress test and an exercise test were performed. The patient rated the general well-being and stated a preference for one of the modes. In the TX mode the heart rate was significantly higher at the end of exercise compared with VVI (107 +/- 4 vs 73 +/- 3 bpm; P less than 0.001) and the exercise tolerance was improved by 9% (104 +/- 8 vs 96 +/- 7 W; P less than 0.01). The patients reported significantly less dyspnea and fatigue at comparable workloads with TX pacing. During the mental stress test the pacing rate increased by 10% in the TX mode (from 73 +/- 2 to 82 +/- 4 bpm; P less than 0.001). There was a physiological rate variability on 24-hour Holter monitoring. Ten patients reported a significant improvement in feeling of general well-being in the TX mode. Eleven patients preferred the TX mode, five patients could not distinguish between the modes and two patients preferred the VVI mode due to worsening of angina pectoris with TX pacing. This preference for the TX mode was significant (P less than 0.05). The results of this controlled study indicate that TX is preferable to VVI in most cases, but the worsening of angina pectoris in two of the patients and the occurrence of rapid rate oscillations in a third patient are factors that warrant some caution in selecting patients.

Changes in QT and Q-aT intervals induced by mental and physical stress with fixed rate and atrial triggered ventricular inhibited cardiac pacing

We have investigated the influence of mental stress and physical stress, i.e., exercise, on the QT and Q-aT intervals (measured from the pacemaker stimulus to the end or the apex, respectively, of the T wave). The study was made on ten patients with high degree atrioventricular block treated with AV universal (DDD) pacemakers. These were programmed to a fixed rate ventricular (VVI) or an atrial triggered (VDD) function for different parts of the study. An arithmetic mental stress test and a bicycle exercise test were performed with each mode of pacing. In the VVI pacing mode, the atrial rate increased by 11% during mental stress and by 46% during exercise. There was a significant shortening of QT and Q-aT intervals with both types of stress. With VDD pacing, mental stress induced a 12% increase in rate and a significant shortening of QT and Q-aT. The paced rate increased by 50% during the exercise test. This increase in ventricular rate was associated with the most marked changes in QT and Q-aT intervals. Thus, both types of stress cause a significant shortening of the QT and Q-aT interval even in the absence of a simultaneous increase in ventricular rate. When the latter is allowed to increase during VDD pacing, both intervals shorten considerably more. There was a marked inter-individual variability in the response to both types of stress. These findings are of importance with regard to the QT sensing rate responsive pacemaker which can be expected to respond to mental stress in most patients, but that response might be unpredictable in the individual.

Influence of the glomerular filtration rate on renal clearance of ceftazidime in cystic fibrosis

The renal handling of ceftazidime was studied in 8 patients with cystic fibrosis and 10 healthy controls. The renal clearance of ceftazidime (CLRcz) was measured after an intravenous single dose and during low and high plasma concentration steady-state infusions. The glomerular filtration rate (GFR) was simultaneously estimated by inulin clearance (CL inul). The average CLRcz (mean +/- SD) was higher in cystic fibrosis patients (125 +/- 20 ml/min/1.73 m2) than in healthy controls (100 +/- 9 ml/min/1.73 m2) [p less than 0.005]. Also CL inul (mean +/- SD) was increased in cystic fibrosis patients (132 +/- 30 ml/min/1.73 m2) compared with healthy controls (103 +/- 8 ml/min/1.73 m2) [p less than 0.02]. The mean renal clearance ratios of ceftazidime to inulin were close to unity after both the single dose and low and high dose steady-state infusions both in cystic fibrosis patients and in controls. These findings suggest that the glomerular filtration rate is the principal determinant of the elimination rate of ceftazidime. However, in all cystic fibrosis patients with a CL inul exceeding 125 ml/min/1.73 m2 the clearance ratio was below unity, indicating tubular reabsorption of ceftazidime occurs in these individuals. The results demonstrate a higher but also more variable GFR in cystic fibrosis patients (74 to 174 ml/min/1.73 m2), resulting in increased and accordingly variable ability to eliminate ceftazidime in cystic fibrosis. However, these pharmacokinetic changes are not large enough to call for special dosage considerations for ceftazidime in cystic fibrosis.

Quinidine reduces biliary clearance of digoxin in man

Quinidine is known to reduce the renal clearance of digoxin, but this effect does not completely explain the influence of quinidine on the total clearance of digoxin. We therefore studied the effect of quinidine administration on biliary clearance of digoxin in five patients with atrial fibrillation. Biliary clearance of digoxin under steady state conditions before and during treatment with quinidine was investigated using a duodenal-marker-perfusion technique. Quinidine caused an average 42% (range 21-65%, P less than 0.02) reduction of the measured biliary clearance of digoxin. We conclude that the biliary effect adds to the previously demonstrated inhibitory effect of quinidine on the renal clearance of digoxin and helps to explain the decrease in total clearance of the drug. This is the first demonstration in man of a pharmacokinetic drug interaction at the level of biliary excretion.

Changes in Q-T and Q-aT intervals at rest and during exercise with different modes of cardiac pacing

The influence of heart rate variation on the Q-T and Q-aT intervals (measured from the onset of the QRS to the end or the apex, respectively, of the T-wave) was studied both at rest and during exercise using different modes of pacing. The studies were made on 21 patients with high-degree atrioventricular block. In seven patients with programmable ventricular inhibited (VVI) pacemakers, an increase in pacing rate during rest produced significant shortening of both Q-T and Q-aT. During observations made at rest and during exercise in 14 patients with fixed rate VVI, atrial rate matched asynchronous (VVIm) or atrial triggered (VAT) pacing. Significant shortening of Q-T and Q-aT intervals occurred during exercise in all pacing modes, but was greatest with VVIm and VAT. The Q-T and Q-aT changes were almost parallel in all situations. For measurements made by two independent observers the coefficient of variation was lower for Q-aT than for Q-T (2.2 versus 2.5) and the correlation coefficient was higher (0.96 versus 0.93), indicating easier identification of Q-aT than of Q-T. This study indicated that changes in Q-T and in Q-aT are influenced by intrinsic factors in addition to the ventricular rate. Atrioventricular synchronization did not seem to influence these changes.

Nortriptyline and debrisoquine hydroxylations in Ghanaian and Swedish subjects

Eleven Ghanaian and 12 Swedish subjects phenotyped with a debrisoquine (D) hydroxylation test were given a single oral dose of nortriptyline (NT). Much the same percentage of the given NT dose was excreted as 10-hydroxy-NT (10-OH-NT) by Ghanaians (43.1%) and Swedes (49.2%). There was a close correlation between plasma clearance of NT by 10-hydroxylation and the D metabolic ratio (D/4-OH-D in urine) in the Ghanaians (rs = -0.95; P less than 0.01) and Swedes (rs = -0.84; P less than 0.01). The E-isomer of 10-OH-NT is the major isomer in both Ghanaians (76% to 92% of total 10-OH-NT) and Swedes (78% to 95%). It is suggested that the E-10-hydroxylation of NT and the 4-hydroxylation of D are similarly coregulated in Ghanaians and Swedes.