Biomedical subjects

A Barchowsky

Publications and source records attributed to A Barchowsky.

At least 37 records · Page 2Linked to original sources

PubMed1997

Asbestos causes translocation of p65 protein and increases NF-kappa B DNA binding activity in rat lung epithelial and pleural mesothelial cells.

The mechanisms of cell signaling and altered gene expression by asbestos, a potent inflammatory, fibrogenic, and carcinogenic agent, are unclear. Activation of the transcription factor, nuclear factor (NF)-kappa B, is critical in up-regulating the expression of many genes linked to inflammation and proliferation. Inhalation models of crocidolite- and chrysotile-induced inflammation and asbestosis were used to study the localization of p65, a protein subunit of the NF-kappa B transcription factor, in sham control rats and those exposed to asbestos. In addition, we investigated, using electrophoretic mobility shift analysis, whether in vitro exposure of rat lung epithelial cells and rat pleural mesothelial cells to asbestos increased binding of nuclear proteins, including p65, to the NF-kappa B DNA response element. Furthermore, translocation of p65 into the nucleus was determined by confocal microscopy. In comparison with sham animals, striking increases in p65 immunofluorescence were observed in airway epithelial cells of rats at 5 days after inhalation of asbestos. These increases were diminished by 20 days, the time period necessary for development of fibrotic lesions. In contrast, although inter-animal variability was observed, immunoreactivity for p65 was more dramatic in the interstitial compartment of asbestos-exposed rat lungs at both 5 and 20 days. Changes in p65 expression in pleural mesothelial cells exposed to asbestos in inhalation experiments were unremarkable. Exposure to asbestos also caused significant increases in nuclear protein complexes that bind the NF-kappa B consensus DNA sequence in both rat lung epithelial and rat pleural mesothelial cells. Using confocal microscopy, we observed partial nuclear translocation of p65 in rat pleural mesothelial cells exposed to asbestos. This partial response contrasted with the effects of lipopolysaccharide, which caused rapid and complete translocation of p65 from cytoplasm to nucleus. Our studies are the first to show the presence of the NF-kappa B system in lung tissue and evidence of activation in vitro and in vivo after exposure to a potent inflammatory, fibrinogenic, and carcinogenic environmental agent.

Animals↗

PubMed1996

src-related tyrosine kinases regulate transcriptional activation of the interstitial collagenase gene, MMP-1, in interleukin-1-stimulated synovial fibroblasts.

OBJECTIVE: To characterize tyrosine kinases that contribute to the transcription of interstitial collagenase. METHODS: Four thousand six hundred fourteen basepairs of the rabbit collagenase promoter region were cloned and sequenced. Plasmids containing collagenase promoter fragments linked to the luciferase reporter gene were transiently transfected into primary rabbit synovial fibroblasts. Regulation of gene activation by inflammatory mediators and tyrosine kinase inhibitors was assessed. To identify specific tyrosine kinases that contribute to collagenase gene expression, v-src was transiently expressed in rabbit synovial fibroblasts along with collagenase promoter constructs, and basal and interleukin-(IL-l)-induced collagenase transcription was assayed. RESULT: An inhibitor of src-related tyrosine kinases, herbimycin A, inhibited increases of collagenase messenger RNA in IL-1- and phorbol myristate acetate-treated fibroblasts. Transcriptional activation of collagenase by IL-1 was also inhibited by herbimycin A. Expression of v-src in synovial fibroblasts enhanced basal and IL-1-inducible transcription. CONCLUSION: Activation of collagenase transcription by inflammatory mediators involves activation of an src-related tyrosine kinase.

Animals↗

PubMed1996

Increased neutrophil adherence to endothelial cells exposed to asbestos.

Inhalation of asbestos may activate the pulmonary endothelium to promote an inflammatory cell phenotype that participates in the development of pulmonary fibrosis. However, little is known about the effects of asbestos on endothelial cell function. Therefore, endothelial cells were exposed to chrysotile and crocidolite asbestos for up to 72 hr to investigate the effects of noncytotoxic concentrations of asbestos on cell function. Noncytolytic concentrations of chrysotile and crocidolite caused localized changes in cell morphology, resulting in activation of endothelial cells to a vacuolated, "spindle-shaped" morphology at sites of fiber deposition. The adherence of neutrophils (PMN) to control and asbestos-treated cultures was examined to determine the functional significance of this altered morphology. Chrysotile asbestos caused a time-dependent, 2- to 4-fold increase in PMN adherence that was localized to spindled endothelial cells in close contact with fibers. Monoclonal antibodies against intercellular adhesion molecule-1 (ICAM-1) inhibited this asbestos-induced PMN adherence. Solution hybridization demonstrated a 2.5-fold increase in steady-state levels of ICAM-1 mRNA in cells exposed to chrysotile asbestos for 8 hr. Exposure to crocidolite asbestos resulted in similar alteration in cell morphology and increase in PMN binding to endothelial cells, while a physically similar nonasbestos fiber, refractory ceramic fiber-1 did not cause morphologic change or increased PMN binding. These data suggest that asbestos fibers can specifically and directly activate endothelial cells, resulting in an activated cell morphology, increased ICAM-1 expression, and enhanced PMN adherence.

Animals↗

PubMed1996

Arsenic induces oxidant stress and NF-kappa B activation in cultured aortic endothelial cells.

Chronic exposure to low levels of environmentally derived arsenite are associated with vascular diseases, such as arteriosclerosis. However, the cellular and molecular mechanisms for vascular disease in response to arsenic are not known. These studies investigated the hypothesis that nonlethal levels of arsenic increase intracellular oxidant levels, promote nuclear translocation of trans-acting factors, and are mitogenic. Incubation of second passage vascular endothelial cells with less than 5 microM arsenite for 4 h increased incorporation of [3H]thymidine into genomic DNA, while higher concentrations failed to stimulate or inhibit DNA synthesis. Within 1 h following addition of noncytotoxic concentrations of arsenite, oxidants accumulated and thiol status increased. During this time period, there was increased nuclear retention of NF-kappa B binding proteins and nuclear translocation of NF-kappa B also occurred in response to 100 microM H2O2. Supershift analysis demonstrated that p65/p50 heterodimers accounted for the majority of proteins binding consensus kappa B sequences in cells treated with arsenite or oxidants. The antioxidants, N-acetylcysteine or dimethylfumaric acid, increased intracellular thiol status and prevented both oxidant formation and translocation of NF-kappa B binding proteins in response to arsenite. These data suggest that arsenite initiates vascular dysfunction by activating oxidant-sensitive endothelial cell signaling.

Animals↗

PubMed1995

Asbestos induces nuclear factor kappa B (NF-kappa B) DNA-binding activity and NF-kappa B-dependent gene expression in tracheal epithelial cells.

Nuclear factor kappa B (NF-kappa B) is a transcription factor regulating expression of genes intrinsic to inflammation and cell proliferation--features of asbestos-associated diseases. In studies here, crocidolite asbestos caused protracted and dose-responsive increases in proteins binding to nuclear NF-kappa B-binding DNA elements in hamster tracheal epithelial (HTE) cells. This binding was modulated by cellular glutathione levels. Antibodies recognizing p65 and p50 protein members of the NF-kappa B family revealed these proteins in two of the DNA complexes. Transient transfection assays with a construct containing six NF-kappa B-binding DNA consensus sites linked to a luciferase reporter gene indicated that asbestos induced transcriptional activation of NF-kappa B-dependent genes, an observation that was confirmed by northern blot analyses for c-myc mRNA levels in HTE cells. Studies suggest that NF-kappa B induction by asbestos is a key event in regulation of multiple genes involved in the pathogenesis of asbestos-related lung cancers.

Animals↗

PubMed1995

Acetylcholinesterase inhibition by zifrosilone: pharmacokinetics and pharmacodynamics.

OBJECTIVE: To determine the pharmacokinetics, pharmacodynamics and safety of the acetylcholinesterase inhibitor zifrosilone in healthy male volunteers. METHODS: Pharmacokinetics, pharmacodynamics, and tolerance of zifrosilone were studied in a double-blind, sequential, single-escalating-dose, randomized panel design. Each panel consisted of six subjects, with four subjects receiving zifrosilone (10, 30, 60, 90, 120, 150, 200, 250, and 300 mg orally) and two subjects receiving matching placebo. Serial blood samples were obtained for zifrosilone plasma concentrations and red blood cell acetylcholinesterase and butyrylcholinesterase activities. Participating subjects (n = 54) were men between the ages of 18 and 45 years. Each subject had a normal physical examination, electrocardiogram, serum chemistries, hematology, urinalysis, and test for human immunodeficiency virus at screening. RESULTS: A greater than proportionate increase in mean plasma concentration values for area under the curve from time zero to infinity was observed over the 200 to 300 mg dose range groups. Red blood cell acetylcholinesterase showed a dose-inhibition relationship, with a mean maximum inhibition of 20.9% at 10 mg that increased to 62.1% at 300 mg. Butyrylcholinesterase activity was relatively unaffected by zifrosilone (< 20% inhibition at 300 mg). For doses > or = 200 mg, an Emax pharmacodynamic model was used to describe the relationship between zifrosilone plasma concentration and red blood cell acetylcholinesterase inhibition (Emax = 83.8%; EC50 = 0.65 ng/ml). CONCLUSIONS: Zifrosilone showed dose-dependent pharmacokinetics after oral administration and was effective in causing selective inhibition of red blood cell acetylcholinesterase.

Acetophenones↗

PubMed1995

A multiple-dose safety trial of eptastigmine in Alzheimer's disease, with pharmacodynamic observations of red blood cell cholinesterase.

A placebo-controlled multiple dose study was conducted to evaluate the safety, tolerability, and pharmacodynamics of multiple dose levels of eptastigmine in 25 patients with probable Alzheimer's disease (AD). Twenty patients (12 M, 8 F; mean age 74, range 57-84) were randomized to receive 12mg (N = 3), 20mg (N = 6), 28mg (N = 6) or placebo (N = 5) tid on a double-blind basis for 14 days, followed by seven days of single blind placebo, in successively rising dose groups. All patients completed the study without intolerable or severe adverse events. All doses significantly (p < 0.001) reduced peak and trough RBC cholinesterase (AChE) activity as compared to baseline. Percent inhibition for Day 14 peak and trough RBC AChE peak and trough values, respectively, appeared proportional to dose: 18% and 21% (12mg); 36% and 35% (20mg); 40% and 44% (28mg). In order to determine the maximum tolerated dose of eptastigmine, an additional single-blind study was performed in five patients (2 M, 3 F; mean age 78, range 72-80) utilizing a rising dose schedule of eptastigmine (N = 4) or placebo (N = 1), starting with the previously tolerated 28mg tid dose and increasing by 4mg tid up to a potential maximum of 56mg tid. Dose-limiting adverse events occurred requiring discontinuation of medication in one patient at 48mg tid and two patients at 52mg tid; RBC AChE inhibition was proportional to dose, with peak values up to 70% inhibition at 48mg tid. The maximum tolerated dose of 48mg tid was identified as a basis for potential Phase II multicenter efficacy trials.

Acetylcholinesterase↗

PubMed1995

Oxidant-sensitive and phosphorylation-dependent activation of NF-kappa B and AP-1 in endothelial cells.

Relatively low concentrations of reactive oxygen cause reversible alterations of endothelial cell signal transduction and gene transcription. The hypothesis that low levels of oxidant stress activate retention of trans-acting proteins in the nucleus was investigated by determining time and dose requirements for oxidant-stimulated nuclear protein binding to consensus DNA sequences for nuclear factor (NF)-kappa B or activator protein 1 (AP-1). Nuclear proteins were extracted from low passage porcine aortic endothelial cells 15 min to 24 h after addition of increasing concentrations of H2O2. Electrophoretic mobility shift assays demonstrated that protein binding to NF-kappa B and AP-1 sequences increases over 1-2 h after stress relative to time-matched controls and resolves by 24 h. The selective protein kinase C inhibitor, calphostin C, prevents approximately 30% of this increase. Inhibition of tyrosine kinase activity by herbimycin A (5 microM) completely inhibits the response to H2O2. Exposure of intact cells to H2O2 increases substrate phosphorylation in pp60src immunoprecipitates. The activity of pp60src in immunoprecipitates from control cells or of recombinant pp60src increases after in vitro addition of H2O2. H2O2-stimulated pp60src activity is reduced by pretreatment of the enzyme preparation with N-acetylcysteine. These data indicate that oxidants increase nuclear levels of trans-acting factors in endothelial cells and that these increases require oxidant-sensitive changes in both tyrosine and serine/threonine phosphorylations.

Animals↗

PubMed1994

Bioactivation of nitroprusside by porcine endothelial cells.

Sodium nitroprusside (Na2[(CN)5FeNO], SNP), which is stable, diamagnetic, and not detectable by electron paramagnetic resonance (EPR) spectroscopy, can be activated by one-electron reduction. The initial product, which retains the five cyanides and is here called penta, has a distinctive EPR signal. Penta spontaneously dissociates the trans-cyanide ligand resulting in a second paramagnetic species called tetra, which has a different and distinctive EPR signal. Tetra is able to transfer its NO ligand to a suitable acceptor, and all four equatorial cyanides subsequently dissociate. However, excess free cyanide shifts the tetra-penta equilibrium in the direction of penta and prevents NO release. This study was an attempt to extend the above results on SNP reduction, which were obtained in a model hemoglobin system, to intact porcine cells by characterizing all EPR-detectable intermediates. When porcine aortic endothelial or smooth muscle cells in culture were incubated under anaerobic conditions with SNP, an EPR spectrum was obtained, which could be resolved into the signal for penta and a signal previously described as a nonheme iron-nitrosyl-sulfur complex, Fe-NOSR. Tetra was not detected. This FeNOSR has some differences in its stability and location from that described by others in activated macrophages. When incubations were carried out under air, penta could not be detected, but a somewhat diminished signal for FeNOSR was still detectable. When incubations were carried out in the presence of excess free cyanide, conditions under which reduced SNP does not nitrosylate hemoglobin, the penta signal became stronger and the FeNOSR signal, though decreased, was still observed. Depletion (95%) of intracellular reduced glutathione in endothelial cells had no effect on the FeNOSR signal strength. We conclude that SNP is activated in porcine endothelial cells by a one-electron reduction to penta, which apparently dissociates its trans-cyanide to form tetra which then goes on to form FeNOSR upon reaction with a membrane-bound thiol. Glutathione is not involved in any of these reactions.

Animals↗

PubMed1994

Oxidant-sensitive protein phosphorylation in endothelial cells.

Reactive oxygen is an important regulator of vascular cell biology; however, the mechanisms involved in transducing signals from oxidants in endothelial cells are poorly defined. Because protein phosphorylation is a major mechanism for signal transduction, cultured aortic endothelial cells were exposed to nonlethal concentrations of H2O2 to examine oxidant-sensitive changes in phosphorylation state. Addition of H2O2 increases the phosphorylation of the heat shock protein 27 (HSP27) within 2 min. This response is maximal by 20 min and remains constant for more than 45 min. Levels of intracellular free Ca2+ in endothelial cells did not change following addition of 100 microM H2O2, nor did the ability of the cells to respond to bradykinin. H2O2-induced phosphorylations were either not affected or were slightly increased in cells pretreated with PKC inhibitors (H-8, staurosporin, or calphostin c). Two-dimensional analysis of phosphoproteins from homogenates of 32P-labeled cells revealed that phorbol myristate acetate (PMA) did not cause the same degree of HSP27 phosphorylation as H2O2. Simultaneous addition of 10 eta M PMA and 50 microM H2O2 decreased the oxidant-stimulated phosphorylation of the most acidic HSP27 isoform. These data suggest that signal transduction for H2O2-sensitive endothelial cell responses are not only independent of PKC, but may also be suppressed by the action of the kinase.

Analysis of Variance↗

PubMed1993

Effects of losartan on blood pressure, plasma renin activity, and angiotensin II in volunteers.

Losartan is an orally active, nonpeptide angiotensin II (Ang II) (site-1) receptor antagonist. We conducted a multiple-dose study in healthy male volunteers to investigate the tolerability, blood pressure effects, and changes in plasma renin activity (PRA) and plasma Ang II concentration associated with once-daily administration of 100 mg losartan for a week. Subjects were studied on a standardized sodium diet (24-hour urinary sodium excretion, 98 +/- 37 [SD] mEq per 24 hours on the placebo run-in day). Measurements of blood pressure, heart rate, PRA, Ang II, and aldosterone were taken during a placebo run-in day and after single and multiple (7 days) daily doses of losartan (100 mg, n = 10) or placebo (n = 4). Ang II was measured specifically by high performance liquid chromatography coupled with radioimmunoassay. In subjects given losartan, respective decreases (systolic/diastolic) from run-in in supine blood pressure 6 hours after dosing were (mean +/- SD), compared with the placebo run-in day, first dose: -8.8 +/- 9.6/-6.8 +/- 5.0, last dose: -11.6 +/- 8.9/-7.0 +/- 4.8 mm Hg (p < 0.05 for all changes). At this 6-hour time point, corresponding increases from run-in in PRA were from 1.2 +/- 0.6 to 12.0 +/- 6.3 (first dose) and 9.6 +/- 4.9 (last dose) ng angiotensin I per milliliter per hour and in Ang II were from 4.3 +/- 1.7 to 72.4 +/- 33.3 and 45.7 +/- 14.1 pg/mL. All changes in PRA and Ang II were statistically significant within the losartan-treated group, and the biochemical changes were significantly greater than those in the placebo-treated group. The increment in Ang II was less after the last dose than after the first (p < 0.05). The drug was well tolerated by all subjects. These data indicate that, under the conditions of this study, losartan administration (100 mg/day for eight doses over 9 days) results in treatment-related decreases in blood pressure and increases in PRA and Ang II octapeptide.

Adolescent↗

PubMed1991

Regulation of arachidonic acid release in vascular endothelium. Ca(2+)-dependent and -independent pathways.

Ca2+ metabolism and its relationship to arachidonic acid release were studied in cultured pig aortic endothelial cells. When cells were treated with bradykinin, a rapid rise in intracellular Ca2+ concentration ([Ca2+]i) occurred. Arachidonic acid release from cells prelabelled with [3H]arachidonic acid and subjected to flow-through conditions closely followed the changes in [Ca2+]i. Attenuation of the Ca2+ response by chelating extracellular and intracellular Ca2+ or by desensitization of receptors led to comparable attenuation of arachidonate release. Activation of protein kinase C inhibited Ca2+ mobilization in response to bradykinin and stimulated arachidonic acid release. Inhibition of protein kinase C had no effect on bradykinin-stimulated arachidonic acid release, suggesting that protein kinase C does not mediate the bradykinin response. The role of GTP-binding regulatory proteins (G-proteins) in mediating the bradykinin response was also investigated. Bradykinin-stimulated arachidonic acid release was not diminished by preincubation with pertussis toxin. Treatment with the G-protein activator AlF4- resulted in the release of a large pool of arachidonic acid and the formation of lysophospholipids. Combined treatment with AlF4- and bradykinin resulted in a greater than additive effect on arachidonic acid release. In contrast with bradykinin, AlF(4-)-stimulated arachidonic acid release was not dependent on the presence of extracellular Ca2+ or the mobilization of intracellular Ca2+. These results demonstrate Ca(2+)-dependent (bradykinin) and Ca(2+)-independent (AlF4-) pathways of phospholipase A2 activation.

Alkaloids↗

PubMed1991

Gossypol effects on endothelial cells and tumor blood flow.

Isomers (-, +) of the antitumor agent gossypol (G) were studied for their ability to reduce tumor ATP and blood flow in rats bearing subcutaneously implanted pancreatic tumors. A 50% reduction in tumor ATP/Pi within ih of a single injection of -G was associated with a 60% decline in tumor blood flow. To determine if these changes in tumor physiology could be due to a direct drug effect on tumor endothelium, G isomers were compared for their ability to alter protein (125I-BSA) permeability and metabolic (32P) labelling of cultured endothelial cells. Treatments for ih produced no endothelial cell leakage, but 24h exposures to either -G (5 microM) or +G (50 microM) produced complete permeability of the monolayers to 125I-BSA. In contrast, 0.5-I.Oh exposures to -G (4 microM) produced 2 to 3-fold increases in phosphorylated 27 kDa heat-shock protein, hsp-27. Hsp-27 phosphoprotein isoforms were differentially labelled following -G and +G exposures with the phosphorylation profile of -G appearing most similar to that of oxyradical producing agents known to induce hsp-27 and injure endothelial cells. We postulate that the tumor ischemic effects of -G are mediated by endothelial response to oxyradical production in a mechanism similar to that of tissue ischemia-reperfusion injury.

Adenosine Triphosphate↗

PubMed1989

Factors affecting free (unbound) lignocaine concentration in suspected acute myocardial infarction.

1. Free plasma lignocaine concentrations were measured for up to 48 h after constant infusion of the drug in 41 subjects with suspected acute myocardial infarction. 2. The free plasma lignocaine clearance at 12 h was significantly and proportionately related to body weight and to the presence of mild (Killip Class II) heart failure, with an 18% reduction in free clearance in the latter condition. 3. The free plasma lignocaine was not related to sex, age or the presence of confirmed acute myocardial infarction, when corrected for the effects of body weight and presence of heart failure. 4. Free plasma lignocaine concentration 1 h after a fixed loading dose were also significantly related to body weight and presence of heart failure but not to sex, age or proven acute myocardial infarction. 5. The data indicate that correction of loading and maintenance infusion for body weight and presence of (even mild) heart failure should somewhat reduce variability in free (and presumably active) plasma lignocaine concentrations but that the free plasma lignocaine concentration at 12 h is most accurately predicted by measuring the free (and to a lesser extent total) plasma lignocaine concentration at 1 h.

Adult↗

PubMed1989

Inhibition of prostaglandin synthesis after metabolism of menadione by cultured porcine endothelial cells.

We have examined the effects of menadione on porcine aortic endothelial cell prostaglandin synthesis. Addition of 1-20 microM menadione caused a dose- and time-dependent inhibition of stimulated prostaglandin synthesis with an IC50 of 5 microM at 15 min. Concentrations greater than 100 microM menadione were necessary to increase 51Cr release from prelabeled cells. Recovery of enzyme inactivated by menadione required a 6-h incubation in 1% serum. In a microsomal preparation, menadione was shown to have no direct effect on conversion of arachidonic acid to prostaglandins. In intact cells menadione caused only a 40% inhibition of the conversion of PGH2 to prostacyclin. Enzymes involved in the incorporation and the release of arachidonic acid were not affected by menadione (20 microM, 15 min). Menadione undergoes oxidation/reduction reactions in intact cells leading to partial reduction of oxygen-forming, reactive oxygen species. In our cells menadione was found to increase KCN-resistant oxygen consumption. Further, an increased accumulation of H2O2 was observed with a time course consistent with menadione-induced inhibition of prostaglandin synthesis. We conclude that menadione at sublethal doses caused inhibition of prostaglandin synthesis. The mechanism involves inactivation of PGH2 synthase by a reactive species resulting from metabolism of menadione by endothelial cells.

Animals↗

PubMed1987

Recovery of porcine aortic endothelial cell prostaglandin synthesis following inhibition by sublethal concentrations of hydrogen peroxide.

Confluent monolayers of porcine aortic endothelial cells exposed for 10 min to 100 microM H2O2 lose their capacity to produce prostaglandins in response to addition of saturating exogenous arachidonic acid. Significant recovery of prostaglandin I2 and E2 synthesis occurred within 3 h and full enzymatic capacity returned by 6 h. Reducing the injury by exposure to half the amount of H2O2 allowed prostaglandin I2 production to recover to a greater extent in 3 h, while cells exposed for 60 min to either 0.5 or 1.0 mM H2O2 demonstrated no recovery. Pre-treatment with either actinomycin D or cycloheximide also prevented recovery following exposure to 100 microM peroxide. Injured cells did not recover when incubated with balanced salts after removal of peroxide, while incubation with medium 199 allowed for the complete return of synthetic capacity. Addition of 1% fetal calf serum in medium 199 did not facilitate recovery. Production of prostaglandins from endogenous arachidonic acid, released by either bradykinin or the ionophore A23187, was also inhibited by H2O2 exposure, however, full recovery of this stimulated synthesis occurred within 3 h. Cycloheximide pre-treatment completely inhibited recovery of bradykinin-induced prostaglandin I2 synthesis. These data demonstrate that sublethal concentrations of H2O2 irreversibly inactivate fatty acid cyclooxygenase and that synthesis of new enzyme is required for recovery. This return of activity occurs more rapidly for production of prostaglandins from endogenous arachidonic acid compared with production following addition of exogenous substrate.

Animals↗

PubMed1987

Inhibition of renin release by analogues of adenosine in rabbit renal cortical slices.

Renal cortical slices obtained from male New Zealand rabbits were used to investigate the role of adenosine in the regulation of renin release. Isoproterenol produced a significant (p less than 0.01), twofold to threefold increase in renin release, that was both dose-dependent and time-dependent. Addition of either the l-phenylisopropyl or the N6-ethylcarboxamido derivative of adenosine attenuated this stimulation at concentrations as low as 10(-9) M or 10(-8) M, respectively. Higher doses of d-phenylisopropyladenosine (10(-6) M) or adenosine (10(-5) M) were necessary to significantly reduce the beta-adrenergic response (p less than 0.01). Inhibition was absent in slices preincubated with 10(-5) M 8-phenyltheophylline, a concentration that had no effect on either basal or stimulated renin release. The site of inhibition appeared to be distal to beta-adrenergic and prostaglandin receptors since l-phenylisopropyladenosine (10(-8) M) blocked stimulation by selective beta-adrenergic receptor agonists, prenalterol (10(-6) M) or salbutamol (10(-5) M), and by prostaglandin E1. These data suggest that adenosine and its analogues inhibit renin release and that this inhibition may be mediated by a receptor-dependent action on a common point in the pathway leading to release.

Adenosine↗

PubMed1985

A free lignocaine index as a guide to unbound drug concentration.

A free lignocaine index was developed on the basis of measurements of plasma lignocaine and its principle binding protein, alpha 1-acid glycoprotein (AAG) in 80 samples from 16 patients admitted to the coronary care unit and given prophylactic lignocaine therapy. The free drug fraction, fu, of lignocaine was determined by equilibrium dialysis and its relationship to AAG and total lignocaine concentration (T) defined by multiple linear regression analysis as l/fu = 1.45 + 0.023 (AAG) -0.129 (T) (multiple r = 0.872, P less than 0.001). This relationship was used to calculate the 'free lignocaine index' as fu X T and compared with the observed value obtained by equilibrium dialysis of 178 samples from 41 separate subjects who received lignocaine after suspected myocardial infarction. There was a highly significant relationship (r = 0.933, n = 178, P less than 0.001) between the observed and predicted values. We conclude that the free drug index may be useful in rapidly assessing the unbound (free) concentration of lignocaine in plasma.

Humans↗