Multilocus linkage of familial hyperkalaemia and hypertension, pseudohypoaldosteronism type II, to chromosomes 1q31-42 and 17p11-q21.

Essential hypertension is a common multifactorial trait. The molecular basis of a number of rare diseases that after blood pressure in humans has been established, identifying pathways that may be involved in more common forms of hypertension. Pseudohypoaldosteronism type II (PHAII, also known as familial hyperkalaemia and hypertension or Gordon's syndrome; OMIM #145260), is characterized by hyperkalaemia despite normal renal glomerular filtration, hypertension and correction of physiologic abnormalities by thiazide diuretics. Mild hyperchloremia, metabolic acidosis and suppressed plasma renin activity are variable associated findings. The pathogenesis of PHAII is unknown, although clinical studies indicate an abnormality in renal ion transport. As thiazide diuretics are among the most efficacious agents in the treatment of essential hypertension, understanding the pathogenesis of PHAII may be of relevance to more common forms of hypertension. Analysis of linkage in eight PHAII families showing autosomal dominant transmission demonstrates locus heterogeneity of this trait, with a multilocus lod score of 8.1 for linkage of PHAII to chromosomes 1q31-q42 and 17p11-q21. Interestingly, the chromosome-17 locus overlaps a syntenic interval in rat that contains a blood pressure quantitative trait locus (QTL). Our findings provide a first step toward identification of the molecular basis of PHAII.

Human hypertension caused by mutations in WNK kinases.

Hypertension is a major public health problem of largely unknown cause. Here, we identify two genes causing pseudohypoaldosteronism type II, a Mendelian trait featuring hypertension, increased renal salt reabsorption, and impaired K+ and H+ excretion. Both genes encode members of the WNK family of serine-threonine kinases. Disease-causing mutations in WNK1 are large intronic deletions that increase WNK1 expression. The mutations in WNK4 are missense, which cluster in a short, highly conserved segment of the encoded protein. Both proteins localize to the distal nephron, a kidney segment involved in salt, K+, and pH homeostasis. WNK1 is cytoplasmic, whereas WNK4 localizes to tight junctions. The WNK kinases and their associated signaling pathway(s) may offer new targets for the development of antihypertensive drugs.

Structure-activity relations of amiloride derivatives, acting as antagonists of cation binding on Na+/K(+)-ATPase.

In a search for an organic analogue of K+ or Na+ ions that binds to the cation binding sites of Na+/K(+)-ATPase with high affinity, the potency of the diuretic amiloride and its derivatives in blocking Rb+ occlusion has been tested. Although amiloride itself has a low affinity (> 200 microM), insertion of short alkyl chains in position 5 of the pyrazine ring of the molecule dramatically increased the affinity of the compound. For example, 5-(N-ethyl-N-isopropyl)amiloride (EIPA) competes with a Ki approximately 10 microM. In derivatives lacking a halogen in position 6 of the ring, a 6-fold decrease in affinity was found. Substitutions in the guanidinium moiety did not produce high affinity inhibitors of Rb+ occlusion. Several derivatives at positions 5 and 6 of the pyrazine ring were found to be strictly competitive inhibitors with respect to Rb+ ions. The highest affinity was observed around pH 8.0-8.2, and low temperature. EIPA and 5-(N-methyl-N-isobutyl)amiloride (MIBA) stabilized the E1 form of FITC1-labelled Na+/K(+)-ATPase, behaving as Na+ analogues. The present findings are similar to our previous results, showing that alkyl- and arylguanidinium derivatives are competitive Na(+)-like antagonists in cation sites. Conclusions concerning the structural features of amiloride derivatives which are necessary to produce the highest binding affinity, are being exploited in synthesis of competitive cation analogues. Derivatives with sufficiently high affinity (0.1-1 microM) will be converted to affinity and photoaffinity reagents.

Dietary sodium intake modulates pituitary proopiomelanocortin mRNA abundance.

The pituitary prohormone proopiomelanocortin gives rise to melanocortins of alpha, beta, and gamma primary structure in addition to corticotropin. Melanocortins have a variety of actions in mammals, and each is natriuretic. In particular, gamma-melanocyte-stimulating hormone has been shown to mediate reflex natriuresis after acute unilateral nephrectomy. We examined whether this peptide could play a role in longer term adjustments in sodium balance by measuring plasma gamma-melanocyte-stimulating hormone and corticotropin concentrations, as well as pituitary proopiomelanocortin mRNA abundance, in Sprague-Dawley rats ingesting either a low (0.07% NaCl) or high (7.5% NaCl) sodium diet. One week after the high sodium diet, plasma gamma-melanocyte-stimulating hormone concentration was double the value seen in rats on the low sodium diet (158 +/- 5 [SE] versus 76 +/- 9 fmol/mL, P < .001), a change that was accompanied by a fivefold increase in plasma atrial natriuretic peptide concentration but no change in plasma corticotropin. Whole pituitary proopiomelanocortin mRNA abundance, measured with a probe to exon 3 of the rat proopiomelanocortin gene, was significantly increased after 1 week of the high sodium diet compared with the low sodium diet and increased further at 2 and 3 weeks. This increase occurred primarily in the neurointermediate lobe as demonstrated by in situ hybridization; the content of gamma-melanocyte-stimulating hormone immunoreactivity was also increased in this lobe, but not the anterior lobe, after 1 week of the high sodium diet. These results demonstrate that high dietary sodium intake increases neurointermediate lobe proopiomelanocortin mRNA abundance compared with a very low sodium diet and also suggest that proopiomelanocortin is preferentially processed into gamma-melanocyte-stimulating hormone rather than corticotropin. These observations consequently raise the possibility of a role for this peptide hormone system in the adjustments to a high salt diet.

Sympathomimetic effects of paraxanthine and caffeine in humans.

Caffeine is metabolized extensively (on average 80%) to paraxanthine. With regular caffeine consumption, average serum levels of paraxanthine are two thirds those of caffeine. Both caffeine and paraxanthine competitively and nonselectively inhibit adenosine receptors in vitro. To examine the contribution of paraxanthine to the pharmacologic activity of caffeine, we administered to 12 subjects in a crossover design oral caffeine (2 or 4 mg/kg) versus placebo or oral paraxanthine (same dose as caffeine) versus placebo, each after 3 days of methylxanthine abstinence. Both caffeine and paraxanthine significantly increased diastolic blood pressure, plasma epinephrine levels, and free fatty acids. Caffeine and paraxanthine produced a similar magnitude of response at 4 mg/kg; however, caffeine appeared to produce greater responses than paraxanthine at 2 mg/kg. Caffeine and paraxanthine have similar sympathomimetic actions. The activity of paraxanthine needs to be considered in understanding the clinical pharmacology of caffeine, particularly with chronic, repetitive caffeine consumption.

Hepatic infarctions during pregnancy are associated with the antiphospholipid syndrome and in addition with complete or incomplete HELLP syndrome.

Antiphospholipid antibody syndrome (APS) is associated with adverse pregnancy outcomes and maternal complications including thrombotic events and early pre-eclampsia. HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) represents a unique form in the spectrum of pre-eclampsia. This report describes four patients with pregnancy-associated hepatic infarctions. All four had APS and HELLP syndrome, which was complete in one patient and incomplete in three patients, with elevated liver enzymes in all, and either thrombocytopenia or hemolysis in two. In the literature, we found descriptions of an additional 24 patients who had 26 pregnancies with concomitant hepatic infarction. Of the total 28 patients, anticardiolipin antibodies (aCL) and/or lupus anticoagulant (LAC) were assessed in 16 patients, out of whom 15 were found to be positive. Hepatic infartction during pregnancy was associated almost always with APS, with HELLP (2/3 complete, 1/3 incomplete), and only in one-third of the pregnancies with pre-eclampsia (PE).

Persistent neonatal hypoglycemia due to hyperinsulinism: medical aspects.

Eight neonates with persistent hypoglycemia were seen over a four-year period and a ninth infant with neonatal onset was treated from 9 months of age. Seven infants had high absolute insulin levels (range 12 to 50 microunits/ml) during hypoglycemia whereas two patients had normal levels which were, however, inappropriate for the low blood glucose levels. Six patients with severe intractable hypoglycemia resistant to intensive medical therapy (including high dose diazoxide) had partial or total pancreatectomy, whereas three with relatively controllable hypoglycemia eventually had spontaneous remissions. In one of the medically treated patients, remission occurred at the unusually early age of 4 months. In the six surgically treated patients and in a seventh patient who had a biopsy only, the pancreas showed characteristic pathologic changes compatible with those described as nesidioblastosis or "endocrine-cell dysplasia." Of the six patients followed up for greater than or equal to 24 months, four have normal psychomotor development, despite periods of arrested head growth in early infancy in three of them.

The pharmacokinetics of morphine and lidocaine in critically ill patients.

OBJECTIVE: To evaluate the pharmacokinetic parameters of morphine and lidocaine after a single intravenous dose in critically ill patients. DESIGN: Prospective, clinical study. SETTING: General intensive care unit (ICU) in a university hospital. PATIENTS: Patients admitted to the ICU with severe systemic inflammatory response syndrome of various etiologies. INTERVENTIONS: A single intravenous dose of morphine (0.025 mg/kg) and lidocaine (1.5 mg/kg) were given separately 12-36 h after admission, and arterial blood samples for serum drug levels were taken. MEASUREMENTS AND RESULTS: Morphine pharmacokinetics were studied in 30 patients. The clearance (Cl) was found to be 5.7+/-2.3 ml/kg per min, volume of distribution of the central compartment (Vc) 0.16+/-0.12 l/kg and volume of distribution at steady state (Vss) 1.08+/-0.69 l/kg. These values are lower then those described previously for healthy volunteers (33.5+/-9 ml/kg per min, 1.01+/-0.31 l/kg, and 5.16+/-1.4 l/kg, respectively), and similar to those described in trauma and burned patients. Lidocaine pharmacokinetics were tested in 24 subjects. The Cl was 6.9+/-3.8 ml/kg per min, Vc 0.25+/-0.1 l/kg and Vss 0.78+/-0.26 l/kg. These values are not different from parameters published previously for healthy volunteers (10 ml/kg per min, 0.53 l/min and 1.32 l/min, respectively). No correlation was found between clinical variables and pharmacokinetic parameters of both drugs (ANOVA). CONCLUSIONS: Both morphine and lidocaine have a reduced volume of distribution in critically ill patients. The normal lidocaine clearance indicates preserved hepatic blood flow and suggests that other mechanisms are involved in the reduced morphine clearance. These findings may have application for the treatment of ICU patients.

Epinephrine pharmacokinetics and pharmacodynamics following endotracheal administration in dogs: the role of volume of diluent.

OBJECTIVE: to define the optimal volume of dilution for endotracheal(ET) administration of epinephrine (EPI). DESIGN: prospective, randomized, laboratory comparison of four different volumes of dilution of endotracheal epinephrine (1, 2, 5, and 10 ml of normal saline). SETTING: large animal research facility of a university medical center. SUBJECTS AND INTERVENTIONS: epinephrine (0.02 mg/kg) diluted with four different volumes (1, 2, 5, and 10 ml) of normal saline was injected into the ET tube of five anesthetized dogs. Each dog served as its own control and received all four volumes in different sequences at least 1 week apart. Arterial blood samples for plasma epinephrine concentration and blood gases were collected before and 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30 and 60 min after drug administration. Heart rate and arterial blood pressure were continuously monitored with a polygraph recorder. MEASUREMENTS AND MAIN RESULTS: higher volumes of diluent (5 and 10 ml) caused a significant decrease of PaO2, from 147 +/- 8 to 106 +/- 10 torr, compared with the lower volumes of diluent (1 and 2 ml), from 136 +/- 10 to 135 +/- 7 torr (P < 0.05). These effects persisted for over 30 min. Mean plasma epinephrine concentrations significantly increased within 15 s following administration for all the volumes of diluent. Mean plasma epinephrine concentrations, maximal epinephrine concentration (Cmax) and the coefficient of absorption (Ka) were higher in the 5 and 10 ml groups. The time interval to reach maximal concentration (Tmax) was shorter in the 5 and 10 ml groups. Yet these results were not significantly different. Heart rate, systolic and diastolic blood pressures did not differ significantly between the groups throughout the study. CONCLUSIONS: Dilution of endotracheal epinephrine into a 5 ml volume with saline optimizes drug uptake and delivery without adversely affecting oxygenation and ventilation.

Atropine pharmacokinetics and pharmacodynamics following endotracheal versus endobronchial administration in dogs.

Emergency endotracheal and endobronchial drug administration provide an effective alternative for intravenous drug delivery during cardiopulmonary resuscitation. The purpose of the present study was to determine the immediate pharmacokinetic and pharmacodynamic properties of atropine following administration by either of these routes. Atropine (0.02 mg/kg) was given to seven anaesthetized mongrel dogs. Each dog was studied twice: once when atropine was injected into the endotracheal tube, and on another day when atropine was given via a flexible catheter wedged into a peripheral bronchus. Plasma atropine concentrations and blood gases were measured during 60 min following drug administration. Both routes of atropine administration differed significantly in three measures: the maximal atropine concentration (Cmax) was significantly higher with the endobronchial administration 40.0 +/- 7.8 ng/ml compared to 23.9 +/- 5 ng/ml endotracheally (P = 0.008); atropine's elimination (t1/2beta) half-life was significantly longer with the endobronchial route (39.3 +/- 5.2 min vs. 28.0 +/- 7.9 min; P = 0.05); Endobronchial administration resulted in an increase of 16% in heart rate, beginning immediately after drug delivery and peaking after 5 min. Other pharmacokinetic parameters were not significantly different. We conclude that endobronchial administration of atropine has a clear advantage over the endotracheal route.

Prolonged therapy by the combination of furosemide and thiazides in refractory heart failure and other fluid retaining conditions.

The efficacy and side effects of the combination therapy of thiazide and furosemide administered to patients with refractory heart failure, for a prolonged period of time, were assessed. Thirty-two patients were hospitalized during the years 1985-1991. Left heart failure (left ventricular ejection fraction (LVEF = 22.4% +/- 6.6%) was present in 26 patients, right heart failure in 3 patients, chronic renal failure, cirrhosis and bilateral pleural effusion were present each in one patient. Chlorothiazide 0.5 g daily was added to conventional therapy. Patients were monitored closely during hospitalization and later as outpatients. During hospitalization, addition of chlorothiazide caused a reduction of 4.8 +/- 4.0 kg in patients' weight, serum potassium decreased from 4.4 +/- 0.6 to 4.0 +/- 0.5 mmol/l (P < 0.005) and serum sodium from 139.0 +/- 4.7 to 136.8 +/- 5.5 mmol/l (P < 0.05). The duration of the combined therapy was 17.2 +/- 19.1 months. Thirteen patients had short treatment (1.6 +/- 0.8 months) and 19 patients had prolonged treatment (26.5 +/- 19.0 months). No specific characteristics distinguished patients in both groups. Thiazides were discontinued in 19 patients, 10 of which had side effects. In only 5 of the 19 patients treated for the prolonged period had thiazides to be discontinued because of side effects. Addition of thiazides to furosemide is efficacious in severe heart failure. The combination should be started during hospitalization. Many patients can be maintained on this combination for a prolonged period of time on an ambulatory basis.

Successful treatment by cyclooxyenase-2 inhibitor of refractory hypokalemia in a patient with Gitelman's syndrome.

Gitelman's syndrome is manifested by hypokalemic alkalosis, hypomagnesemia, hypocalciuria, normotensive hyperreninemia and hyperaldosteronism. Hypokalemia can at times be refractory to treatment. We present a patient refractory to a variety of drugs including indomethacin, the nonspecific COX inhibitor. Rofecoxib, a specific COX 2 inhibitor, promptly elevated serum potassium concentration with normalization of plasma aldosterone and near normalization of renin without a change in serum magnesium. Our patient also had rhabdomyolysis, a rarely reported complication, which was also ameliorated by COX 2 inhibition.

Acquired hemophilia masked by warfarin therapy.

People without hemophilia but with autoantibodies specifically directed against the procoagulant activity of factor VIII are known to have acquired hemophilia. The bleeding diathesis in these patients is often severe and life-threatening. The definite laboratory diagnosis of this disorder includes demonstration of low factor VIII levels in plasma with a high titer of factor VIII inhibitors, but the initial suspicion for its presence should rise in view of a prolonged partial thromboblastin time (PTT) and a normal prothrombin time associated with an acquired bleeding disorder. Oral anticoagulant treatment is known to prolong PTT as well, and the merger of these 2 situations may cause delayed diagnosis of acquired hemophilia with devastating consequences. We describe here the first reported case of acquired hemophilia diagnosed in a patient treated with warfarin. In such patients prolonged PTT may be ascribed to warfarin therapy rather than to acquired hemophilia, thus causing a dangerous delay in diagnosis.

Cardiac conduction defects associated with hyponatremia.

Cardiac conduction defects have not been previously described in association with hyponatremia, although in patients with congestive heart failure the frequency of ventricular premature beats was found to correlate to the severity of hyponatremia. We describe three patients with second-degree or complete atrioventricular (AV) block which occurred during or shortly after an episode of severe hyponatremia. The first had thiazide-induced hyponatremia while on amiodarone. In the second, definite etiology for hyponatremia which was associated with longstanding polydipsia could not be established. The third had ischemic heart disease and intermittent conversion of his first-degree to second-degree AV block while hyponatremic after diuretics use. Although it is usually difficult to single out hyponatremia as the cause of conduction defects which usually occur in the presence of cardiac disease, potent medications or other electrolyte abnormalities, we suggest that hyponatremia may play a role in the pathogenesis of conduction defects in the diseased heart.

The pharmacokinetics of morphine and lidocaine in nine severe trauma patients.

STUDY OBJECTIVE: To study the pharmacokinetic parameters of morphine and lidocaine after a single intravenous (i.v.) bolus in severe trauma patients. DESIGN: Clinical case study. SETTING: Department of Anesthesiology and Intensive Care of a university hospital. PATIENTS: Nine patients, ages 24 to 91 years (mean 54.4 yrs), admitted to the hospital with severe trauma (Injury Severity Score > 20) were included in the study. INTERVENTIONS: After initial evaluation and stabilization, a single i.v. dose of morphine 0.025 mg/kg and lidocaine 1.5 mg/kg was given separately, and blood samples were drawn for each drug serum concentration. MEASUREMENTS AND MAIN RESULTS: Morphine pharmacokinetics was studied in eight patients, lidocaine pharmacokinetics in seven patients, and both drugs were studied in six patients. Morphine clearance 2.5 to 10 ml/kg/min (6 +/- 2.6, mean +/- SD) and volume of distribution 0.28 to 3.30 L/kg (1.4 +/- 1.0) were found to be lower than values described previously for healthy volunteers (33.5 +/- 9 ml/kg/min and 5.16 +/- 1.40 L/kg, respectively), and are similar to those described in trauma patients (5 +/- 2.9 ml/kg/min and 0.9 +/- 0.2 L/kg, respectively). In contrast, lidocaine clearance 4.5 to 9.4 ml/kg/min (6.7 +/- 1.7) and volume of distribution 0.39 to 1.20 L/kg (0.72 +/- 0.28) were similar to the value described in healthy volunteers (10 ml/kg/min and 1.32 L/kg, respectively). CONCLUSION: Changes in pharmacokinetics of drugs eliminated by the liver may occur in patients with severe trauma. The preserved lidocaine clearance indicates an almost normal hepatic blood flow and suggests that other mechanisms may be involved in the lower morphine clearance. The findings may have applications for the treatment of severe trauma patients and suggest that drug monitoring might be needed in some instances so as to avoid toxicity.

[Actinobacillus actinomycetemcomitans endocarditis].

Bacterial endocarditis caused by Actinobacillus actinomycetemcomitans (AA) is an extremely rare disease. AA, a gram negative cocco-bacillus, normally resides in the oral cavity. It is involved mostly in local oral cavity infections, but severe systemic infections caused by it have been reported. We describe a 63-year-old man with endocarditis caused by AA which probably originated from a dental abscess. The course of the disease was complicated by acute myocardial ischemia, apparently caused by coronary artery embolism. To enable growth of this bacterium, blood cultures should be maintained for 2-3 weeks in a CO2-rich atmosphere.