Possible interaction between imipramine and butalbital.

A 44-year-old woman was admitted to the psychiatric unit for exacerbation of her depressive disorder. Blood concentrations of her antidepressant, imipramine, were within normal range and consistent with past concentrations. Her medical history was significant for a chronic headache disorder for which she was given a prescription containing butalbital on admission. The patient's depressive disorder was quickly controlled but relapsed 2 weeks later. Concentrations of imipramine showed a decrease of approximately 50%. Imipramine is metabolized in the liver by the cytochrome P-450 (CYP 1A2) system, and barbiturates are known inducers of this enzyme subset. To our knowledge, an interaction specifically between butalbital and imipramine has not been documented; however, these drugs are extensively prescribed and occasions may arise where they are given concurrently. We recommend repeat measurement of imipramine concentrations 1 week after the start of any butalbital-containing product or barbiturate, and dosage adjustments based on the results and on the patient's response to the change.

Role of C/EBP proteins in hepatic and vascular smooth muscle transcription of human NHE1 gene.

We have recently shown that regulatory element D (nucleotides -239 to -215) of the 0.25-kb promoter of the human growth factor-activatable Na+/H+ exchanger (NHE1) is important for gene transcription in cells of hepatic origin (Hep G2) and vascular smooth muscle origin (VSM A7r5). This element contains a sequence (nucleotides -230 to -222) with complete homology to the C/EBP binding site. We now demonstrate that nucleotide substitution mutations disrupting this C/EBP site suppressed transcription in Hep G2 cells, VSM A7r5 cells, and Sprague-Dawley VSM cells in primary culture. These mutations abolished the binding of rat liver nuclear activities as well as transcription factors C/EBP alpha, C/EBP beta, and C/EBP delta expressed in COS-1 cell lysates to element D. Anti-C/EBP antibodies supershifted DNA-protein complexes formed between hepatic nuclear activities or C/EBP proteins expressed in COS-1 cell lysates and regulatory element D. Finally, cotransfection experiments of NHE1 0.25-kb promoter-chloramphenicol acetyltransferase (CAT) construct and C/EBP expression vectors showed that C/EBP alpha and C/EBP delta are transactivators of the NHE1 proximal promoter in Hep G2 and VSM A7r5 cells. These results indicate that members of the C/EBP family of transcription factors are involved in the regulation of hepatic and vascular smooth muscle transcription of the human NHE1 gene.

Adjunctive treatments in schizophrenia: pharmacotherapies and electroconvulsive therapy.

Substantial proportions of patients with schizophrenia do not achieve acceptable levels of response with antipsychotic therapy alone, which commonly leads clinicians to use additional somatic interventions. This article reviews the literature on the use of adjunctive pharmacological treatments and electroconvulsive therapy (ECT) in schizophrenia. The authors find that, despite a large volume of literature, it is difficult to draw conclusions or treatment recommendations from available data because of small sample sizes and widely divergent study designs. At present, there is little firm evidence that adding adjunctive agents to standard neuroleptics will dramatically change the somatic treatment of schizophrenia. The most promising adjunctive agents are benzodiazepines, lithium, and carbamazepine, as well as antidepressants and ECT for affective symptoms. Future inpatient research on adjunctive treatments should be multicenter studies, followed by long-term outpatient trials that assess quality-of-life issues as well as symptom relief.

Experimental renal failure in the rat modulates cardiac Na,K-ATPase alpha 2 mRNA but not protein.

The decreased abundance and enzymatic activity of myocardial Na,K-ATPase have been recognized previously to occur in chronic uremia. However, the activity of the cardiac sodium pump as defined by the uptake of 86Rb is normal. The discrepancies between these findings may have resulted from the inability to distinguish between the different Na,K-ATPase isoforms now known to exist in cardiac muscle. To investigate this question, steady-state levels of Na,K-ATPase alpha and beta mRNA isoforms, alpha 1, alpha 2, and beta 1 protein, and specific high-affinity binding of [3H]ouabain were quantitated in cardiac muscle from uremic and pair-fed, sham-operated control rats. Steady-state levels of alpha 2 and beta 2 mRNA were significantly decreased (percentage of control levels: alpha 2, 48 +/- 10; beta 2, 74 +/- 9; N = 10; P < 0.025) in chronic renal failure without any change in alpha 1, alpha 3, or beta 1 expression. The number of high-affinity [3H]ouabain-binding sites and Na,K-ATPase alpha 1, alpha 2, and beta 1 subunits was not different from control. In acute renal failure, alpha 2 and beta 2 mRNA levels also were significantly decreased (percentage of control levels: alpha 2, 24 +/- 5; beta 2, 44 +/- 8; N = 6; P < 0.001), but there was no change in the level of alpha 3 or beta 1 mRNA, the number of high-affinity [3H]ouabain-binding sites, or the level of Na,K-ATPase alpha 2 and beta 1 subunits.(ABSTRACT TRUNCATED AT 250 WORDS)

Proximal regulatory elements and nuclear activities required for transcription of the human Na+/H+ exchanger (NHE-1) gene.

We herein demonstrate competence of the 5' upstream region -1374 to +16 of the human growth factor-activatable Na+/H+ exchanger (NHE-1) gene to promote transcription of the chloramphenicol acetyltransferase gene in cells of hepatic origin (HepG2), vascular-smooth-muscle origin (VSM A7r5) and fibroblasts (3T3). We also describe the mapping of the regulatory elements required for such transcription. Sequential 5' end-deletions indicated that the 5' boundary of the positive regulatory elements of NHE-1 transcription is localized downstream of nucleotide -252 in both HepG2 and VSM A7r5 cells but downstream of nucleotide -654 in 3T3 cells. Footprinting analysis of the 0.25-kb promoter fragment using rat liver nuclear extracts identified 4 protected regions as follows: A, -31 to -9; B, -108 to -65; C, -124 to -111; and D, -239 to -215. Internal deletion and nucleotide substitutions within regulatory element D revealed its essential role for transcription of the human NHE-1 gene in HepG2 and VSM A7r5 cells. DNA binding and competition assays using rat liver nuclear extracts indicated that regulatory element D is recognized by 5 nuclear activities. Four of these activities (designated as NHE-1D1-4) are competed out completely by oligonucleotides containing the binding sites of transcription factors CREB, AP3, NFY, and other CCAAT box-binding proteins (C/EBP alpha or related proteins). This competition profile might be explained by the presence of homology between regulatory element D and the consensus sequence of C/EBP as well as the other competitor oligonucleotides. The actual relationship between these nuclear activities and the C/EBP family of proteins (or other transcription factors) remains to be determined.

Stimulation of basolateral Na(+)-HCO3- cotransporter by angiotensin II in rabbit renal cortex.

Angiotensin (ANG) II is now recognized as a powerful direct controller of Na+ reabsorption in the proximal convoluted tubule, a property that predominantly reflects stimulation of the transepithelial NaHCO3 flux. Numerous studies have established that this effect of ANG II represents stimulation of the apical Na+/H+ exchanger, but a single microperfusion study has also suggested direct stimulation of the basolateral Na(+)-HCO3- cotransporter. We have carried out studies in basolateral membrane vesicles from rabbit renal cortex to examine directly whether ANG II exerts an independent effect on the Na(+)-HCO3- cotransporter. Preincubation of vesicles with ANG II (10(-11) to 10(-9) M) for 15 min enhanced the activity of the cotransporter, the greatest effect occurring at 10(-11) M (41 +/- 1.1%, P < 0.005). This stimulation reflected an increase in the maximal enzyme reaction velocity of the cotransporter but no change in the Michaelis constant for Na+. ANG II had no effect on Na(+)-dependent succinate transport. ANG I (10(-9) M) and ANG III (10(-10) M) also stimulated the Na(+)-HCO3- cotransporter, and captopril (10(-4) M) attenuated the ANG I stimulation by 68 +/- 3.5% (P < 0.01) but not that of ANG II and III. Saralasin (10(-11) to 10(-8) M) by itself behaved as an agonist, and its stimulation was additive to that by ANG II. The nonpeptide ANG II receptor antagonist, losartan potassium (10(-6) M), and the disulfide-reducing agent, dithiothreitol (10 mM), each by itself had no effect on the cotransporter but each markedly attenuated the ANG II effect (by 77 +/- 1.4%, P < 0.01 and 74 +/- 1.6%, P < 0.005, respectively) in accord with the view that the basolateral receptor belongs to subtype 1. These results identify physiological concentrations of ANG II as a potent, direct, and specific stimulator of the basolateral Na(+)-HCO3- cotransporter.

Endothelin-1 stimulates the Na+/H+ and Na+/HCO3- transporters in rabbit renal cortex.

Endothelin-1 (ET-1) is the most potent endogenous vasoconstrictor identified to date, raising the strong possibility of its involvement in the pathogenesis of systemic hypertension. Whether ET-1 exerts a direct stimulating effect on sodium reabsorption in the renal proximal convoluted tubule, the dominant locus of sodium reabsorption in the nephron, is currently unknown. Such an effect would suggest yet another mechanism by which ET-1 might mediate systemic hypertension. In studies on membrane vesicles prepared from rabbit renal cortex, we show that ET-1 (10(-8) to 10(-11) M) exerts dose-dependent stimulation of the apical Na+/H+ exchanger and the basolateral Na+/HCO3- cotransporter; preincubation of vesicles with 10(-10) M ET-1 for five minutes enhanced the activity of each transporter by approximately 25%. This stimulation reflected an increase in the Vmax of each transporter but no change in the Km for sodium. The stimulatory effect of ET-1 was blocked in the presence of an ET-1 antiserum. Moreover, the stimulation of the apical Na+/H+ exchanger and the basolateral Na+/HCO3- cotransporter by ET-1 displayed specificity as indicated by the lack of effects on the activities of the apical Na(+)-glucose transporter and the basolateral Na(+)-succinate transporter. The data implicate ET-1 as a novel, direct and specific modulator of sodium reabsorption in the proximal tubule. As such, ET-1 might be a direct determinant of extracellular fluid volume under normal and pathophysiologic circumstances, including hypertensive disorders.

The effects of clozapine on tardive dyskinesia.

This article reviews eight published studies that describe clozapine's effects on TD and examines the outcome of 30 patients with TD treated with clozapine for up to 36 months. These data indicate that TD response to clozapine is variable but that approximately 43% of cases, particularly those with dystonic features, improved after clozapine treatment. Methodological limitations of the studies described, however, preclude definitive conclusions, which must await appropriately controlled trials.

Rat kidney band 3 mRNA modulation in chronic respiratory acidosis.

Recent evidence indicates the existence of a protein related to the erythroid chloride-bicarbonate exchanger (band 3 protein) in the basolateral aspect of type A intercalated cells of the distal nephron. To probe the possible participation of this transporter in the renal adaptation to chronic hypercapnia, we examined the steady-state abundance of band 3 mRNA in the kidney during respiratory acidosis of variable duration. Total RNA was isolated from renal cortex and medulla of rats maintained in a 10% CO2 atmosphere for 2 or 5 days and from contemporaneous controls. The RNA was analyzed by Northern blot assay using cDNA probes for band 3 and beta-actin genes. Using a 3' cDNA probe encoding the membrane-associated domain of band 3 protein that is involved in anion exchange, we found a two- to threefold increase in steady-state mRNA levels (whether or not correction for the beta-actin signals was applied) in renal cortex and medulla at 5 days of hypercapnia. Similar, but less definitive, increases were observed at the 2-day time point. Using a 5' cDNA probe encoding an erythroid-protein segment absent from the kidney band 3 major transcript, we detected meager hybridization in renal tissue and no measurable variation during hypercapnia. Use of splenic RNA as a positive control for the 5' probe disclosed marked reduction of band 3 mRNA levels in hypercapnia, indicating organ specificity of band 3 gene expression. We conclude that steady-state levels of kidney band 3 mRNA increase in chronic respiratory acidosis as a result of transcriptional or posttranscriptional regulatory mechanisms. This adaptation might be involved in the augmentation of renal acidification characteristic of chronic hypercapnia.

Effect of chronic respiratory acidosis on urinary calcium excretion in the dog.

It is currently believed that the two chronic acidemic disorders exert disparate effects on urinary calcium excretion: chronic metabolic acidosis induces consistent hypercalciuria, but no appreciable change or even a decrease in calcium excretion is reported to attend chronic respiratory acidosis. Whereas the effect of metabolic acidosis is well documented, little work has been carried out in chronic hypercapnia. In fact, most of the studies on chronic respiratory acidosis were short in duration, had employed only mild hypercapnia, or had failed to control carefully the prevailing metabolic conditions. We have carried out balance observations in nine dogs exposed to a 10% CO2 atmosphere in an environmental chamber for a period of two weeks. Chronic respiratory acidosis led to a significant increase in urinary calcium excretion from a mean control value of 0.4 +/- 0.1 mmol/day to 0.6 +/- 0.1 mmol/day during both week 1 and 2 of hypercapnia (P less than 0.05). Hypercalciuria occurred even though filtered load of calcium fell. Mean fractional excretion of calcium increased significantly during each week of hypercapnia averaging 0.60 +/- 0.12% during control, 1.05 +/- 0.13% during week 1, and 1.26 +/- 0.17% during week 2 of hypercapnic exposure (P less than 0.05). There were no changes in plasma levels of immunoreactive parathyroid hormone or 1,25-dihydroxyvitamin D3. These findings suggest that chronic respiratory acidosis, just like chronic metabolic acidosis, augments urinary calcium excretion by a direct depressive effect on the tubular reabsorption of calcium.

Adaptation of rabbit renal cortical Na+-H+ exchange activity in chronic hypocapnia.

We have examined the activity and kinetic characteristics of the Na+-H+ exchanger in renal cortical brush-border membrane vesicles (BBMV) prepared from rabbits adapted to chronic hypocapnia in order to address whether this transporter might contribute to the suppressed proximal bicarbonate reabsorption characteristic of this disorder. Chronic hypocapnia was induced by exposing animals to 9% O2 for a 5-day period. In comparison with paired, contemporaneous controls, an average delta PaCO2 of 13 mmHg and an average delta [HCO3-] of 7.3 meq/l were obtained. Chronic hypocapnia led to a significant suppression of the 22Na+ uptake by BBMV; at the 3-s mark, a 30% suppression was observed (chronic hypocapnia, 4.05 +/- 0.43 nmol/mg protein; control, 5.72 +/- 0.39 nmol/mg protein) (P less than 0.01). A significant decrease in the Vmax of the antiporter was noted (chronic hypocapnia, 622.7 +/- 86.8 nmol.mg protein-1.min-1; control 857.5 +/- 64.8 nmol.mg protein-1.min-1) (P less than 0.01), whereas the Km for sodium remained unaltered. The specificity of this adaptation was supported by showing that Na+-dependent uptake of D-[3H]glucose by BBMV was not significantly different between chronic hypocapnia and control. Chronic normocapnic hypoxemia left Na+-H+ exchange activity undisturbed. We conclude that the observed change in the BBMV Na+-H+ antiporter might be responsible, at least in part, for the suppressed renal bicarbonate reabsorption characteristic of chronic hypocapnia and that a consequence of the hypocapnic state itself mediates this adaptation.

Clozapine: guidelines for clinical management.

The advent of antipsychotic drugs represented a milestone in psychotherapeutics. Despite their proven efficacy, antipsychotic drugs are limited by side effects and treatment resistance in some patients. Since the introduction of chlorpromazine and the subsequent development of numerous neuroleptic compounds, there have been no significant qualitative advances in the clinical efficacy of antipsychotic drugs. Clozapine is an experimental neuroleptic with atypical properties. In clinical testing, this agent has shown superior antipsychotic efficacy in treatment-refractory schizophrenics and a more favorable extrapyramidal side effect profile in comparison with standard neuroleptics. Because clozapine represents a potential contribution to our therapeutic armamentarium, this article provides an overview of its pharmacology, efficacy, and methods of clinical utilization.

Techniques for isolation of brush-border and basolateral membrane vesicles from dog kidney cortex.

Two methods are reported for renal membrane preparation from the dog kidney cortex. One method is a simultaneous preparation of brush-border (BBMV) and basolateral (BLMV) membranes. Using readily available laboratory equipment, differential centrifugation produced a supernatant which was treated with Mg2+. The Mg2+ treatment produced a pellet (crude BLMV) which was added to Percoll and centrifuged to produce purified BLMV. The supernatant after Mg2+ treatment eventually yielded pure BBMV after additional Mg2+ precipitations. The second method used an acidic medium in conjunction with divalent-cation precipitation to prepare BBMV. Whichever method was used, BBMV and BLMV showed appropriate enzyme and transport activities.

Cyclic-AMP production by polymorphonuclear leukocytes in psychiatric disorders.

The cyclic adenosine monophosphate (cAMP) responses to histamine, prostaglandin-E1, and isoproterenol in polymorphonuclear leukocytes from drug-free normal controls and patients with schizophrenia or major depressive disorder were compared. These three groups of subjects did not differ in their cAMP responses to receptor activation. Exacerbated and remitted patients with either schizophrenia or major depressive disorder did not differ in their cAMP responses. The data indicate that in polymorphonuclear leukocytes, the cAMP responses to activation of histamine H2, prostaglandin-E1, or beta-adrenergic receptors are neither state-independent nor state-dependent markers for schizophrenia or major depressive disorder.