The use of human liver banks in pharmacogenetic research.
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Genetic Markers↗
Biomedical subjects
C Nordin
Publications and source records attributed to C Nordin.
E-10-hydroxynortriptyline: effects and disposition of a potential novel antidepressant.
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Animals↗
Electrophysiologic characteristics of single myocytes isolated from hypertrophied guinea-pig hearts.
To determine whether the electrical changes associated with cardiac hypertrophy are due to alterations in the membrane properties of individual hypertrophied cells, we recorded action potentials in single myocytes isolated from normal and hypertrophied hearts. Cardiac hypertrophy was produced by a gradual pressure overload created by placing a band around the ascending aorta in young guinea-pigs (200-250 g). Almost half the animals that developed left ventricular (LHV) hypertrophy also developed evidence of cardiac dysfunction. Action potentials were recorded with standard microelectrodes in single ventricular myocytes isolated by enzymatic dispersion of the heart. The action potential duration at 1 Hz was significantly longer in hypertrophied cells than in control cells. The degree of action potential prolongation in isolated cells did not correlate with the degree of hypertrophy but did correlate with the degree of myocardial disease, the duration being longer in hypertrophied myocytes from dyspneic than in those from non-dyspneic animals. The resting potential was significantly lower in hypertrophied myocytes from dyspneic animals than in hypertrophied cells from non-dyspneic animals or control cells stimulated at 5 Hz. The relationship between the frequency of stimulation (0.33, 1, and 5 Hz) and action potential duration was steeper in hypertrophied than normal myocytes. The mean membrane capacitance (cm) of hypertrophied myocytes increased by 31% over the control value. Thus, isolated hypertrophied myocytes retain the prolonged duration of the action potential and the exaggerated dependence of duration on rate observed in intact hypertrophied muscle. The increased duration of the action potential in hypertrophied cells cannot be readily attributed to the observed increase in cm. Our results indicate that the membrane changes responsible for the altered electrical properties of hypertrophied myocardium are due to an effect of hypertrophy on individual myocytes and that the prolonged duration of the action potential is probably due to changes in active currents flowing during repolarization.
Action Potentials↗
Hyperlipoproteinemia in spontaneously diabetic guinea pigs.
A colony of Hartley guinea pigs that exhibit hyperglycemia, glucosuria, and hypertriglyceridemia characteristic of human diabetes mellitus was developed. Initially, a group of guinea pigs that had normal serum glucose concentrations (less than or equal to 200 mg/dL of serum) at 3 to 4 weeks of age was obtained; however, in some of the animals progressively severe hyperglycemia (300 to 500 mg/dL of serum) and glucosuria (greater than 2 g of glucose/24 h) occurred as the animals matured. In addition, the animals exhibiting hyperglycemia and glucosuria had plasma insulin concentrations that were similar to those animals that were not hyperglycemic. The diabetic animals were found to be hypertriglyceridemic, with plasma triglyceride levels of 140 to 290 mg/dL at four months of age. Nondiabetic animals (plasma glucose concentration of less than or equal to 200 mg/dL and no glucosuria) had plasma triglyceride concentrations between 37 and 76 mg/dL. Lipoprotein analysis of plasma from nondiabetic and diabetic animals indicated that the diabetics had a fourfold increase in VLDL triglyceride and protein concentrations. The VLDL had an abnormal apolipoprotein composition and had reduced levels of apoprotein-E. The progeny from the mating of diabetic males and females also exhibited the diabetic trait, suggesting that the origin of the disease is genetic. This colony of guinea pigs is being further investigated as a suitable model for the study of the hyperlipoproteinemia of human noninsulin-dependent diabetes mellitus.
Animals↗
Disposition of perphenazine is related to polymorphic debrisoquin hydroxylation in human beings.
The pharmacokinetics of a single oral dose of 6 mg perphenazine was studied in a group of six slow and six rapid hydroxylators of debrisoquin. Peak serum concentrations of perphenazine were significantly higher in slow hydroxylators than they were in rapid hydroxylators (2.4 +/- 0.6 versus 0.7 +/- 0.3 nmol/L, p less than 0.001). The AUC(0-12) was also higher in slow hydroxylators than it was in rapid hydroxylators (18.5 +/- 6.2 versus 4.5 +/- 2.5 nmol.L-1.hr, p less than 0.001). The data suggest that the disposition of the antipsychotic drug perphenazine covaries with polymorphic debrisoquin hydroxylation.
Administration, Oral↗
Stereoselective disposition of racemic E-10-hydroxynortriptyline in human beings.
The disposition and elimination kinetics of the enantiomers of E-10-hydroxynortriptyline (E-10-OH-NT) were studied in six rapid and four slow hydroxylators of debrisoquin after a single oral dose of 75 mg racemic E-10-OH-NT hydrogen maleate. The plasma levels and the AUC of unconjugated (-)E-10-OH-NT were two to five times higher than those of (+)E-10-OH-NT. The plasma half-lives of both enantiomers were 8 to 9 hours. A significantly higher proportion of the given dose of (+)E-10-OH-NT (64.4% +/- 12.1%) than of (-)E-10-OH-NT (35.3% +/- 9.7%) was recovered in urine as glucuronide conjugate, but more (-)E-10-OH-NT was recovered unchanged in urine. The total oral plasma clearance and the metabolic clearance by glucuronidation were significantly (p less than 0.0001) higher for (+)E-10-OH-NT than for (-)E-10-OH-NT. The findings indicate that first-pass glucuronidation of E-10-OH-NT is enantioselective in human beings in vivo, with preference for (+)E-10-OH-NT. The renal clearance of unbound (-)E-10-OH-NT (0.57 +/- 0.16 L.kg-1.hr-1), on the other hand, exceeded that of (+)E-10-OH-NT (0.44 +/- 0.14 L.kg-1.hr-1) (p less than 0.005), which suggests enantioselective tubular secretion. The debrisoquin hydroxylation status was not associated with any of the investigated kinetic processes that relate to E-10-OH-NT.
Administration, Oral↗
Compensatory hypertrophy and failure in gradual pressure-overloaded guinea pig heart.
Left ventricular hypertrophy has been produced in the guinea pig by a procedure that gradually increases left ventricular afterload. A mildly constricting band was placed around the ascending aortas of very young guinea pigs (225-275 g). With growth to 500-1,000 g, left ventricular systolic pressure increased and left ventricular hypertrophy developed. In approximately 50% of these animals, the hypertrophy was associated with normal left ventricular function and with no unusual symptoms or evidence of heart failure. The other animals developed dyspnea, which appeared an average of 41 days after banding. Dyspneic animals had normal body weight, markedly increased right ventricular and lung weights, decreased left ventricular norepinephrine content, diminished maximum left ventricular pressure generating capacity, and a significantly higher incidence of left ventricular interstitial and perivascular fibrosis. These findings demonstrate that even when left ventricular overload is imposed gradually by banding the aortas of young animals, myocardial decompensation ultimately ensues in a significant proportion of such animals. The slow imposition of loading, the slow rate of decompensation, and the ability to identify animals in heart failure by clinical dyspnea make this model uniquely valuable for studies on the mechanisms of heart failure.
Adaptation, Physiological↗
Relationships between clinical symptoms and monoamine metabolite concentrations in biochemically defined subgroups of depressed patients.
In 28 patients with primary depression, relationships were sought between rating scores on the Montgomery-Asberg Depression Rating Scale and the concentrations of the monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylglycol (HMPG) in cerebrospinal fluid (CSF). Among the single items in the rating scale, reported sadness correlated negatively with HMPG. No other significant relationships were found in the total group of patients. However, in subgroups with low or high concentrations of monoamine metabolites, several significant relationships were found, such as a negative correlation between inner tension and concentration difficulties, respectively, and 5-HIAA in the low-HMPG subgroup. Curvilinear relationships were found between pessimistic thoughts and 5-HIAA in the high-5-HIAA subgroup and between apparent sadness and 5-HIAA in the low-HMPG subgroup. Suicidal thoughts tended to correlate in a curvilinear way with the ratio of HMPG/5-HIAA in the low-HVA and the high-HMPG subgroups, but the curves were mirrored. The results indicate that relationships between clinical symptoms and monoamine metabolite homeostasis in CSF are qualitatively and quantitatively different in defined high-and low-monoamine subgroups of depressed patients.
Depressive Disorder↗
Arrhythmogenic interaction between low potassium and ouabain in isolated guinea-pig ventricular myocytes.
1. The two-microelectrode method of voltage clamp was used in single myocytes isolated from guinea-pig ventricles to investigate the mechanism underlying the arrhythmogenic interaction between low external K+ and digitalis. 2. We investigated the effects of ouabain (10(-6) M) with 4 mM-K+ or 2 mM-K+ on the peak magnitude of the inward component of oscillatory current (Iti) recorded upon repolarization to the resting potential after depolarizing clamps to -5 mV, and on the characteristics of the steady-state current-voltage relationship. 3. Whereas ouabain with 4 mM-K+ did not alter the current-voltage relationship from its control shape, ouabain with 2 mM-K+ caused marked changes in the curve: the zero-current intercept was shifted in a negative direction, the region of low slope conductance was extended to more negative potentials, and the curve was shifted downward relative to the control current-voltage relationship. The changes in the current-voltage relationship induced by ouabain with 2 mM-K+ were very similar to those induced by 2 mM-K+ alone. 4. The functional consequence of the changes in the current-voltage relationship induced by ouabain with 2 mM-K+ was a highly significant reduction in the amount of outward current (Ith) needed to reach the threshold for excitation; Ith was reduced from 1.6 +/- 0.4 nA (n = 6) in ouabain with 4 mM-K+ to 0.8 +/- 0.3 nA (n = 5) in ouabain with 2 mM-K+. 5. The mean value for Iti was larger in ouabain with 2 mM-K+ (0.58 +/- 0.41 nA, mean +/- S.D., n = 4) than in ouabain with 4 mM-K+ (0.42 +/- 0.38 nA, n = 5). Although the increase in Iti was not statistically significant because of the large variability of the measurement, it is possible that the increase might be physiologically significant. 6. Our results suggest that the arrhythmogenic interaction between digitalis and low K+ is due to the combined effects of low K+ on the current-voltage relationship and on the size of the peak inward current induced by ouabain. Whereas the effect of low K+ and ouabain on the inward current was highly variable, the effects on the current-voltage curve were far more consistent, pointing to an important role for alterations in the current-voltage relationship in the arrhythmogenic interaction between low K+ and ouabain.
Action Potentials↗
Sniffing of ethyl chloride--an uncommon form of abuse with serious mental and neurological symptoms.
Abuse of ethyl chloride is a problem which has previously been almost unknown in Sweden. Confusion, hallucinosis, ataxia, and pronounced impairment of short-term memory--all of a transient nature--and a prolonged and uncharacteristic course of abstinence reactions are some of the symptoms that occur on sniffing of ethyl chloride. The course of events in one such case is described. The authors request that references to this article outside the professional press should not be made in such a way as to facilitate abuse.
Ataxia↗
Clinical and biochemical effects during treatment of depression with nortriptyline: the role of 10-hydroxynortriptyline.
Plasma concentrations of nortriptyline (NT) and its major metabolite 10-hydroxy-NT (10-OH-NT) were measured in 30 patients with depression, treated with NT for 3 weeks. Nine patients who recovered completely had plasma concentrations of NT and 10-OH-NT ranging from 358 to 728 nmol/L and from 428 to 688 nmol/L, respectively. Of the 21 patients who did not recover completely, only four had plasma concentrations within the window limited by these two plasma concentration ranges. A correlation was found between the degree of amelioration and the plasma concentration of NT (rs = 0.469; P less than 0.01). Lumbar punctures were performed in 26 patients before and after 3 weeks of NT treatment. During treatment there was a 30.9% mean decrease in the noradrenaline metabolite 4-hydroxy-3-methoxyphenylglycol (HMPG) in cerebrospinal fluid (CSF). We could not evaluate the extent to which this decrease was caused by NT or 10-OH-NT, respectively, because both are strong inhibitors of noradrenaline uptake. The ratio between the concentration of NT and 10-OH-NT in CSF correlated to the reduction of HMPG in CSF (r = 0.397; P less than 0.05) and to the amelioration of depression (rs = 0.623; P less than 0.001). This might indicate that NT and 10-OH-NT interact on the noradrenaline system in a nonadditive way. During treatment there was a 15.2% decrease in CSF concentration of the serotonin metabolite 5-hydroxyindoleacetic acid. The reduction was significantly correlated to the CSF concentration of NT but not to that of 10-OH-NT. This is in accordance with the fact that NT is a more potent inhibitor of serotonin uptake than is 10-OH-NT. The dopamine metabolite homovanillic acid in CSF decreased significantly by 10.0%. The biochemical data indicate that noradrenergic, serotoninergic, and dopaminergic systems are affected by NT treatment and that 10-OH-NT might be more selective on noradrenergic neurons than the parent drug.
Administration, Oral↗
Little anticholinergic effect of E-10-hydroxynortriptyline compared with nortriptyline in healthy subjects.
Six healthy male subjects were randomly given nortriptyline (NT) (25 and 50 mg) and placebo in a double-blind, crossover study. An NT dose of 50 mg (but not 25 mg) clearly reduced saliva flow (P less than 0.05) and was therefore used for comparison with the major and active metabolite of NT, E-10-hydroxynortriptyline (E-10-OH-NT). Equimolar doses of both compounds (and placebo) were randomly given to eight healthy male subjects in another double-blind, crossover study aimed to assess the reduction of saliva flow. NT significantly depressed saliva flow compared with both placebo (P less than 0.01) and E-10-OH-NT (P less than 0.05). By contrast, there was no difference between E-10-OH-NT and placebo. This study confirms previous indications that the anticholinergic effect of E-10-OH-NT is considerably less than that of the parent drug NT.
Adult↗
No interaction of diazepam on amitriptyline disposition in depressed patients.
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Adult↗
Effects of nortriptyline and its 10-hydroxy metabolite on plasma noradrenaline (NA) concentrations, heart rate and blood pressure during intravenous NA infusion.
Eight healthy subjects were randomly given placebo and equimolar doses of nortriptyline (NT) and E-10-hydroxy-NT (E-10-OH-NT). Two hours after oral intake of drug, noradrenaline (NA) was infused intravenously at three consecutive rates. Before infusion of NA, E-10-OH-NT significantly increased heart rate compared to NT (p less than 0.05) and placebo (p less than 0.01). During NA infusion, the active drugs caused non-significant tendencies to augmented increase of blood pressure and decrease of heart rate. Plasma NA concentrations increased significantly due to the infused NA but were not influenced by NT or E-10-OH-NT. This absence of drug effect may have been due to several simultaneously operating factors affecting plasma NA concentrations, e.g., modification of the rates of NA release and clearance by exogenous NA or drugs and competing elimination pathways for infused NA. After stopping the NA infusion, a non-significant tendency to a slower elimination of NA was found after both active drugs.
Adult↗
Tolerance and pilot pharmacokinetics of amiflamine after increasing single oral doses in healthy subjects.
Oral doses of 1 to 100 mg amiflamine, a new reversible monoamine oxidase type A-selective inhibitor, were given for the first time in humans to six healthy men. No apparent pharmacologic effects were recorded until the 80 mg dose. After 100 mg, one subject developed symptoms indicative of an overdose. Amiflamine is extensively metabolized by two consecutive N-demethylations. The biotransformation patterns in plasma and urine were found to correlate with the debrisoquin metabolic ratio.
Adult↗
Disposition of single oral doses of E-10-hydroxynortriptyline in healthy subjects, with some observations on pharmacodynamic effects.
The active and major metabolite of nortriptyline (NT), E-10-hydroxynortriptyline (E-10-OH-NT), was taken orally as the hydrogen maleate in single doses by nine healthy subjects. The doses (10 to 100 mg) were completely absorbed, as shown by the high urinary recovery of 86.1% +/- 9.9%. Of the given dose, 51.2% +/- 8.7% was recovered as conjugated E-10-OH-NT and 23.9% +/- 4.3% was recovered as unchanged compound. The plasma t1/2 of E-10-OH-NT was 8.0 +/- 1.2 hours and total plasma clearance was 47.5 +/- 10.3 L/hr. The rate of elimination varied little between individuals. There was no indication of dose-dependent elimination. The mean apparent volume of distribution was 7.7 +/- 2.1 L/kg. Single oral doses of 50 mg E-10-OH-NT significantly increased the plasma levels of norepinephrine in both the supine and standing positions (P less than 0.01). Pulse rate increased in the standing but not the supine position. These effects might result from inhibition of neuronal uptake of norepinephrine by E-10-OH-NT. Coupled with its low affinity for muscarinic receptors, these kinetic and pharmacodynamic features of E-10-OH-NT call for further phase I studies.
Administration, Oral↗
Analysis of tricyclic antidepressants in serum and plasma yields similar results.
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Amitriptyline↗
Plasma concentrations of nortriptyline and its 10-hydroxy metabolite in depressed patients--relationship to the debrisoquine hydroxylation metabolic ratio.
In 20 depressed patients treated with nortriptyline (NT) there was a significant relationship between the plasma concentration of NT and the debrisoquine metabolic ratio (rs = 0.77; P less than 0.01). (The debrisoquine test was performed after stopping NT treatment). This is in agreement with the hypothesis that the hydroxylations of NT and debrisoquine are mediated by similar enzymatic mechanisms. In contrast there was no significant relationship between the debrisoquine metabolic ratio and the plasma concentrations of the active metabolite 10-hydroxy-nortriptyline. In 11 of the patients the debrisoquine metabolic ratio was significantly higher during than after NT treatment. This may be due to an inhibition of the debrisoquine hydroxylation by NT.
Debrisoquin↗