Normalization of depressed heart function in rats by ribose.

Severe constriction of the abdominal aorta and simultaneous injection of isoproterenol in rats induced depression in heart function and reductions in cardiac adenosine triphosphate and total adenine nucleotides. When ribose was continuously infused for 24 hours, biosynthesis of cardiac adenine nucleotides was stimulated to such an extent that the reductions in adenosine triphosphate and total adenine nucleotides were prevented and left ventricular hemodynamic parameters were normal. These results support the hypothesis that adenosine triphosphate is primarily responsible for depression in myocardial contractility and that ribose is cardioprotective through its pronounced effects on adenine nucleotide metabolism in heart muscle.

Ribose intervention in the cardiac pentose phosphate pathway is not species-specific.

Ribose is cardioprotective in the rat in a variety of pathophysiological conditions. The metabolic basis for this effect is the low capacity of the oxidative pentose phosphate pathway in the myocardium. Ribose bypasses this pathway, elevates the available pool of 5-phosphoribosyl-l-pyrophosphate, and thus stimulates the biosynthesis of adenine nucleotides. In this study reported here the activity of glucose-6-phosphate dehydrogenase, the first and rate-limiting enzyme of the oxidative pentose phosphate shunt, was very low in the human heart and was of the same order of magnitude in the myocardium of various animal species. Furthermore, ribose had a similar stimulating effect on myocardial adenine nucleotide biosynthesis in the guinea pig, in which hemodynamic parameters are different from those in the rat. It is concluded that the metabolic basis for the effectiveness of ribose is similar in all species investigated.

Reduction of the isoproterenol-induced alterations in cardiac adenine nucleotides and morphology by ribose.

Continuous intravenous infusion of ribose (200 milligrams per kilogram per hour) for 24 hours induced a marked stimulation of cardiac adenine nucleotide biosynthesis in unanesthetized and unrestrained rats that had been treated with isoproterenol subcutaneously (25 milligrams per kilogram). The diminution of adenine nucleotides characteristic for the action of high doses of isoproterenol was entirely prevented, and the incidence of the isoproterenol-induced myocardial cell damage was significantly reduced when ribose was administered. These results support the view that depletion of adenine nucleotides is involved in the development of cardiac necrosis.

Induction of antibodies to nuclear antigens in rabbits by immunization with hydralazine-human serum albumin conjugates.

The antihypertensive drug hydralazine can induce in man a syndrome similar to spontaneous systemic lupus erythematosus (SLE). The pathogenesis of this drug-induced syndrome is not understood. In this investigation, five groups of rabbits were studied: group I, 10 rabbits hyperimmunized with hydralazine conjugated to human serum albumin (HSA) in complete Freund's adjuvant (CFA); group II, four rabbits with HSA in CFA; group III, four rabbits with CFA alone; group IV, five rabbits with hydralazine conjugated to rabbit serum albumin (RSA); and group V, four rabbits with a major metabolite of hydralazine conjugated to HSA. The rabbits immunized with hydralazine-HSA developed rising titers of antibodies to hydralazine and progressively increasing amounts of antibodies to both single-stranded and native DNA. The antibodies to DNA were cross-reactive with hydralazine as determined by inhibition of DNA binding and DNA hemagglutination tests. Similar results were obtained in rabbits immunized with the metabolite-HSA compound except the major hapten antibody response was to the metabolite. The DNA antibodies in this group were also capable of being absorbed by metabolite-HSA as well as hydralazine-HSA, indicative of the cross-reactivity between hydralazine and its metabolite. Immunization with hydralazine-RSA caused rabbits to produce antibodies to hydralazine but not to DNA, indicating the requirement for an immune response to the carrier protein in order for antibodies reactive with DNA to be produced. Thus, hyperimmunization of rabbits with hydralazine-protein conjugates may provide a useful animal model of SLE. The data suggests that an immune response to hydralazine may be important in human hydralazine-induced SLE.

Subchronic alpha- and beta-adrenergic regulation of cardiac gap junction protein expression.

Gap junction channels are essential for intercellular electrical communication in the heart. The most important cardiac gap junction proteins are connexin43 (predominantly) (Cx43), connexin40 (Cx40), and in early developmental stages connexin45. Since catecholamines play an important role in cardiac (patho)physiology, we wanted to elucidate whether catecholamines may affect expression of Cx43 and Cx40. Cultured neonatal rat cardiomyocytes were exposed for 24 h to increasing concentrations of noradrenaline (1-10000 nM) (physiological agonist at alpha and beta-adrenoceptors), resulting in significantly increased Cx43-expression, while Cx40 was unaffected. In further experiments cells were incubated with either phenylephrine (alpha-adrenergic agonist) or isoproterenol (beta-adrenergic agonist) (0.1-1000 nM) for 24 h. Both catecholamines lead to a concentration-dependent increase in Cx43 protein and mRNA expression (EC50: 10-20 nM). Inhibition experiments showed that the phenylephrine effect was transduced via PKC, while the isoproterenol effect was mediated by PKA. Dual whole-cell voltage clamp demonstrated that increased Cx43-expression was accompanied by significant increases in gap junction current. In additional in vivo experiments, adult rats were subjected to 24-h infusion of isoproterenol or phenylephrine showing again significant increase in Cx43 but not Cx40. Adrenergic stimulation of cardiomyocytes can enhance Cx43 expression thereby increasing cellular coupling, indicating a possible role for catecholamines in the regulation of cardiac gap junction expression in cardiac disease.

Catecholamine-induced cardiac hypertrophy: significance of proto-oncogene expression.

The effect of beta- and alpha-adrenergic stimulation on cardiovascular function and development of cardiac hypertrophy was studied in rats by measuring the heart weight/body weight and cardiac RNA/DNA ratios. Beta-receptor stimulation with isoproterenol over 3 days induced an increase in the biosynthesis of cardiac adenine nucleotides, myocardial protein synthesis, and the heart weight/body weight ratio. The isoproterenol-induced metabolic effects were prevented by simultaneous beta-adrenergic blockade with propranolol. Alpha-adrenergic stimulation with norfenephrine for 3 days induced an increase in heart rate, total peripheral resistance, the myocardial RNA/DNA, and left ventricular weight/body weight ratio. The calcium antagonist verapamil prevented the hemodynamic changes but did not influence the development of cardiac hypertrophy. The alpha-adrenergic blocker prazosin reversed the norfenephrine-induced functional changes and prevented cardiac hypertrophy. Norepinephrine was infused into isolated perfused working rat hearts to elucidate some molecular biological changes that precede the development of cardiac hypertrophy. It increased transiently and sequentially the mRNA of c-fos and c-myc. This enhancement occurred at about the same time as that induced by elevation of pre- and afterload but was more pronounced. These findings were compared with those obtained in other studies assessing the effects of catecholamines on proto-oncogene expression. Combination of norepinephrine with pre- and afterload elevation induced the c-fos mRNA signal to appear earlier, to be more pronounced, and to persist for a longer period of time. Similar results were obtained in regard to the c-myc mRNA. These findings indicate that the combination of two hypertrophy-inducing stimuli which may cause a higher degree of cardiac hypertrophy in vivo induce an earlier, more pronounced, and longer lasting expression of the proto-oncogenes c-fos and c-myc.

Comitogenic effect of catecholamines on rat cardiac fibroblasts in culture.

OBJECTIVE: We studied the ability of norepinephrine and of other catecholamines to affect the proliferation of cardiac fibroblasts isolated from adult rat hearts. Furthermore, we investigated the possible adrenergic receptor involved in this process. METHODS: Norepinephrine (NE), phenylephrine (PE), isoproterenol (ISO), forskolin (FO), epidermal growth factor (EGF), platelet-derived growth factor AA (PDGF-AA) and specific inhibitors of the alpha(1)-, alpha(2)-, beta(1)- and beta(2)-adrenoceptors and of the protein kinase A (PKA) were applied to cardiac fibroblasts in culture. Cell number was measured by use of a Coulter Counter. Activation of the cAMP response element binding protein (CREB) was measured by Western blotting and subsequent use of a phospho-specific antibody. Activation of the p42- and the p44-mitogen activated protein kinase (p42/p44(MAPK)) was assessed by detection of phosphorylation shifts and by incorporation of 32P-labelled phosphate into myelin basic protein. RESULTS: Fibroblasts isolated from hearts of adult rats were grown in 10% serum-containing media which induced an increase in cell number by 94%. After 48 h, treatment with 10 microM NE caused an even greater increase in cell number by 222%, i.e. another 128% (comitogenic effect). In contrast, NE alone had no effect on the growth of serum-deprived cells. EGF and PDGF-AA did not replace serum as the basic mitogen. After addition of NE to proliferating cells under serum conditions, there was a rapid, time-dependent significant activation of the p42/p44(MAPK) and of CREB for up to 60 and 120 min, respectively. In both cases, the maximum of activation was reached after 5 min. Application of FO (0.1-20 microM) caused a strong activation of CREB, while no increase in the phosphorylation of the p42/p44(MAPK) was detected. Treatment with 20 microM FO led to an identical increase in cell number as application of NE. Specific blockade of PKA with RpcAMPS prevented the activation of CREB and also the comitogenic effect of FO as well as of NE. The alpha- and beta-adrenergic receptor blocker carvedilol (10 microM) normalized all NE-induced effects. Prazosin and yohimbine, inhibitors of alpha(1)- and alpha(2)-adrenoceptor activation, respectively, did not influence the NE-evoked increase in cell number. In contrast, the non-selective beta-adrenoceptor blocker propranolol (1 microM) completely suppressed the comitogenic effect of NE. A similar effect was obtained with the specific beta(2)-adrenoceptor blocker ICI 118,551 (5 microM), while the beta(1)-adrenoceptor blocker metoprolol did not influence the increase in cell number. CONCLUSIONS: NE elicits a comitogenic effect on cultured rat cardiac fibroblasts which is prevented by beta(2)-adrenergic blockade. The activation of CREB contributes to the increase in proliferation. The p42/p44(MAPK) which was also found to be activated by NE might as well be involved in the regulation of the comitogenic effect.

Functional and metabolic effects of ribose in combination with prazosin, verapamil and metoprolol in rats in vivo.

Ribose improves the function of the rat heart in various pathological conditions through its effects on cardiac energy metabolism, while having no direct haemodynamic actions. We therefore studied its functional and metabolic effects in closed chest rats when given in combination with prazosin, verapamil or metoprolol, all of which have direct effects on the circulation. Ribose administration for 24 h at 200 mg.kg-1.h-1 did not affect heart function but increased the available pool of 5-phosphoribosyl-1-pyrophosphate in heart (four fold) and skeletal muscle (1.7-fold), as assessed by the incorporation of 14C-adenine into the adenine nucleotides. The utilisation of adenine for adenine nucleotide synthesis, expressed as the ratio of adenine nucleotide radioactivity to tissue extract radioactivity, was 70% in heart and 20% in skeletal muscle under control conditions, and 97% and 88% after 24 h of ribose administration. Ribose decreased the 14C-adenine incorporation into the adenine nucleotides in kidney, lungs and liver. After 24 h infusion of prazosin (100 micrograms.kg-1.h-1), heart rate and LVdP/dtmax were not changed, but LVSP (-20%), mean aortic pressure (-16%) and peripheral resistance (-40%) were decreased. Cardiac output was enhanced (+40%). Verapamil (2mg.kg-1.h-1) and metoprolol (2mg.kg-1.h-1) infused for 24 h decreased the pressure-rate and pressure-volume product of the left ventricle to the same extent (-40%). Verapamil had no influence on cardiac output, while metoprolol depressed it (-30%). Simultaneous administration of prazosin, verapamil or metoprolol with ribose did not affect the ribose induced increase in the myocardial 5-phosphoribosyl-1-pyrophosphate pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of catecholamines on function of the rat right heart.

OBJECTIVE: Although the haemodynamic effects of catecholamines on the rat left ventricle have been investigated extensively, only few systematic in vivo studies have been performed on the right ventricle. The aim was to examine the acute effects of noradrenaline and isoproterenol on rat right ventricular function. METHODS: Haemodynamic variables were measured during acute, 20 minute infusion of noradrenaline (0.1 mg.kg-1 x h-1) or isoproterenol (12 micrograms.kg-1 x h-1) in female Sprague Dawley rats. To estimate the contribution of alpha and beta receptor stimulation to these effects, eight rats each were infused with prazosin (0.1 mg.kg-1 x h-1), metoprolol (1.0 mg.kg-1 x h-1), or the alpha and beta antagonist carvedilol (0.5 and 1.0 mg.kg-1 x h-1) alone and in combination with noradrenaline or isoproterenol. RESULTS: Noradrenaline and isoproterenol increased right ventricular systolic pressure (RVSP) from 30.3 (SEM 0.5) (n = 32) to 72.7(2.7) (n = 24) and 72.3(4.4) (n = 8) mm Hg, right ventricular (RV) dP/dtmax from 1848(70.3) to 4058(301) and 3612(366) mm Hg.s-1, and heart rate from 329(6) to 371(6) and 420(8) beats.min-1, respectively. Metoprolol completely prevented the isoproterenol induced haemodynamic changes, but neither metoprolol nor prazosin was able to significantly affect the pressure effect of noradrenaline (noradrenaline + metoprolol: 67.3(6.9) mm Hg, noradrenaline + prazosin: 67.0(3.8) mm Hg). The combination of both blockers, however, prevented the noradrenaline induced rise in RVSP (noradrenaline + metoprolol + prazosin: 36.5(5.1), and noradrenaline + prazosin + metoprolol: 30.0(1.2) mm Hg). Carvedilol (1.0 mg.kg-1 x h-1) significantly attenuated the noradrenaline induced RVSP increase (39.1(3.0) mm Hg), but not to the control range. Metoprolol or carvedilol completely prevented the noradrenaline elicited increases in heart rate (254(7) and 287(20) min-1) and RVdP/dtmax, but prazosin alone had no effect on the heart rate and RVdP/dtmax increase. Thus beta receptor blockade alone failed to significantly influence the noradrenaline induced increase of RVSP despite prevention of the increase in heart rate and RVdP/dtmax. Prazosin had a significant effect on RVSP only in combination with metoprolol. CONCLUSIONS: The combined effect of both alpha and beta blockade exceeds the pure addition of the single effects in the rat right ventricle. Moreover, we speculate that the failure to reduce the noradrenaline induced increase in RVSP by either alpha or beta blockade alone is due to the stimulation of the receptor that is not affected by the respective blocker.

Effect of pressure and volume overload on proto-oncogene expression in the isolated working rat heart.

OBJECTIVE: The aim was to study the effect of pressure and volume overload on the expression of the proto-oncogenes, c-fos and c-myc, in isolated perfused working rat hearts and to compare these results with the known effects of noradrenaline. METHODS: Working rat hearts were obtained by converting the Langendorff preparation into the working mode by perfusion through the left atrium. Using specific cDNA clones, the mRNAs of c-fos and c-myc were measured by northern blots and quantified with densitometry. Total RNA was isolated from hearts after stimulation with noradrenaline (3 x 10(-8) M), after increasing afterload from 80 to 100 cm H2O, and left atrial filling pressure (preload) from 8 to 16 cm H2O for 15, 30, 60, 90, and 120 min, respectively. RESULTS: The mRNAs of c-fos and c-myc were not detectable in freshly excised rat hearts. When the hearts were perfused in the working mode for 15, 30, 60, 90, and 120 min, c-fos and c-myc mRNAs were measurable, and these mRNA levels served as control baseline values that were set at 100%. When noradrenaline was infused, c-fos mRNA was increased fivefold after 30, threefold after 60, and 3.8-fold after 90 min. The mRNA of c-myc was increased 1.8-fold after 60 min and 3.8-fold after 90 min. The increase in afterload induced a threefold increase of c-fos mRNA after 30 min and a threefold increase of c-myc mRNA after 90 min. When preload was increased, c-fos mRNA rose 1.8-fold after 30 min, and c-myc mRNA twofold after 60 min and 2.8-fold after 90 min compared to the controls. CONCLUSIONS: Pressure and volume overload have effects on the expression of c-fos and c-myc mRNA that are similar to those obtained with noradrenaline stimulation which induced the most pronounced signals. Our time course studies showed that c-fos mRNA always rose before c-myc mRNA. This common sequential induction pattern may have important signal function in the processes that trigger the development of cardiac hypertrophy.

Serum depletion induces cell loss of rat cardiac fibroblasts and increased expression of extracellular matrix proteins in surviving cells.

OBJECTIVE: Since reduced nutrient supply is one component of ischemia, we have studied the effect of serum depletion on the survival of fibroblasts isolated from adult rat hearts and on the expression and degradation of extracellular matrix (ECM) proteins. Furthermore, we measured the role of the cAMP-dependent pathway in these processes. METHODS: Isolated cardiac fibroblasts were grown to confluency in 10% serum containing medium. Serum was then removed and cell number was measured by use of a Coulter Counter. The activity of the cAMP response element binding protein (CREB) was investigated by Western blotting and subsequent use of the specific antibody which binds to the active form of the protein. The expression of colligin, collagen I and III, matrix metalloproteinases 2 (MMP-2), and tissue inhibitor of matrix metalloproteinase 2 (TIMP-2) was examined by ribonuclease protection assay (RPA) and Western blotting. Zymographic measurements were done to investigate gelatinase activity of MMP-2. RESULTS: Serum withdrawal caused the death of 36% of the cells during the first 8 h. CREB was strongly phosphorylated 5 min after serum removal. Activation persisted up to 8 h and decreased thereafter. The mRNA abundance of colligin, collagen I and III, MMP-2, and TIMP-2 started to increase after 5 and 10 h, respectively, reaching a maximum after 20-30 h and decreasing thereafter. Protein levels of collagen I, collagen III, colligin and TIMP-2 were higher after 24 h until up to 96 h. MMP-2 zymographic activity was elevated 15-fold after 72 h. Application of the protein kinase A (PKA) blocker RpcAMPS suppressed the increase in phosphorylation of CREB. The increase in collagen III and MMP-2 mRNA abundance and elevation of collagen I and III, and TIMP-2 protein was diminished by RpcAMPS. The rise of colligin protein was completely suppressed. The increase in MMP-2 zymographic activity was also attenuated. RpcAMPS improved survival rate from 56 to 84%. CONCLUSIONS: Serum depletion led to cell death of isolated cardiac fibroblasts. Survival was associated with the increase in the expression of various ECM proteins. The transcription factor CREB was activated after serum removal. Inhibition of PKA improved the serum depletion induced decrease in the survival rate. The increase in collagen I, collagen III, MMP-2, TIMP-2, and colligin evoked by serum depletion was also diminished by PKA inhibition.

Different response of the rat left and right heart to norepinephrine.

The in vivo hemodynamic and morphologic responses of the rat left (LV) and right (RV) ventricle to continuous long-term i.v. infusion of norepinephrine (NE) at different dosages and for different durations of infusion were studied. Female Sprague-Dawley rats received continuous intravenous infusion of norepinephrine from infors syringe pumps for 24, 48 and 72 h at a dose of 200 mu g center dot kg-1 x h-1. Furthermore, NE was infused for 72 h at dosages of 50, 100 and 200 mu g center dot kg-1 x h-1. The beta-adrenergic blocker and vasodilator with alpha1-blocking activity carvedilol (0.5 mg x kg-1 x h-1) was coinfused with NE for 72 h. The hemodynamic effects were measured on intact, anesthetized rats with special Millar ultraminiature pressure tip catheters, and the weights of the left and right ventricles were measured. NE increased heart rate at any time or dose, whereas cardiac output and total peripheral resistance remained unchanged. LV and RV dP/dtmax were nearly doubled as compared to control values and RVSP was elevated by more than 100%. The effect of NE on LVSP was much less pronounced (< 20%) and only significant at 50 mu g x kg-1 x h-1 for 72 h. Neither LV nor RV end-diastolic pressures were elevated, indicating that cardiac failure had not occurred. The LV developed hypertrophy with an increase of the ventricular weight/body weight ratio (LVW/BW) of 22% even after only 2 days of NE (200 mu g x kg-1 center dot h-1). The RV showed no hypertrophy at any time of the experiments. The NE-induced changes in HR, dP/dtmax, RVSP and LVW/BW were completely prevented by the coinfusion of carvedilol. These studies show that the hemodynamic responses to continuous infusion of NE are more pronounced in the RV than in the LV. Conversely, NE induced hypertrophy only in the LV, not in the RV. The hemodynamic effects of chronic NE infusion did not change significantly between 1 and 3 days of infusion. The in vivo responses to exogenous NE therefore were unaffected by adaptive effects such as downregulation of adrenergic receptors.

Cardiac remodeling after long term norepinephrine treatment in rats.

OBJECTIVE: In this study we have tested the hypothesis that degradation of collagen by matrix metalloproteinase 2 (MMP-2) precedes the deposition of extracellular matrix (ECM) after long term norepinephrine (NE) treatment. METHODS: Female Sprague-Dawley rats received continuous i.v. infusion of NE (0.1 mg/kg.h) for 1, 2, 3, 4 and 14 days. Heart function and weight as well as expression of cardiac colligin and of collagen I and III were examined. Furthermore, we have assessed the degradation pathway of collagen by measuring the mRNA and activity of myocardial MMP-2 and tissue inhibitor of metalloproteinase 2 (TIMP-2) as well as the protein level of TIMP-2. RESULTS: NE induced hypertrophy predominantly of the left ventricle (LV) in a time-dependent manner. It increased the mRNAs of colligin, collagen I and III, and of MMP-2 and TIMP-2 as well as MMP-2 activity in two phases: In the initial phase, at 3 and 4 days, the mRNA of colligin and of collagen I and III was elevated predominantly in the LV, MMP-2 and TIMP-2 mRNA, as well as TIMP-2 protein and MMP-activity were increased in both ventricles. The second phase, after 14 days, was characterized by a less pronounced increase in colligin, collagen I and III and in MMP-2 activity which occurred exclusively in the LV. Finally, long-term treatment with NE induced a 37% increase in interstitial fibrosis which was shown to occur exclusively in the LV after 14 days. CONCLUSION: NE treatment induced fibrosis exclusively in the LV which was associated with hypertrophy predominantly of the LV. The elevated MMP-2 activity seems to be necessary for the ECM to adapt to the enlargement of myocytes and to reduce overproduction of collagen.

Bioaccumulation and molecular effects of sediment-bound metals in zebrafish embryos.

Predicting the bioavailability and effects of metals in sediments is of major concern in context with sediment risk assessment. This study aimed to investigate the bioavailability and molecular effects of metals spiked into riverine sediments to zebrafish (Danio rerio) embryos. Embryos were exposed to a natural and an artificial sediment spiked with cadmium (Cd), copper (Cu), nickel (Ni) and zinc (Zn) individually or as a mixture at concentrations ranging from 150 to 3000 mg/kg dry weight (dw) over 48 h, and uptake of metals was determined. Furthermore, transcript abundances of the metallothioneins MT1 and MT2, the metal-responsive element-binding transcription factor (MTF) and the genes sod1, hsp70 and hsp90α1 were measured as indicators of metal-induced or general cellular stress. D. rerio embryos accumulated metals from sediments at concentrations up to 100 times greater than those spiked to the sediment with the greatest bioaccumulation factor (BAF) for Cu from artificial sediment (275.4 ± 41.9 (SD)). Embryos accumulated greater concentrations of all metals from artificial than from natural sediment, and accumulation was greater when embryos were exposed to individual metals than when they were exposed to the mixture. Exposure of embryos to Zn or the mixture exhibited up to 30-fold greater transcript abundances of MT1, MT2 and hsp70 compared to controls which is related to significant uptake of Zn from the sediment. Further changes in transcript abundances could not be related to a significant uptake of metals from sediments. These studies reveal that metals from spiked sediments are bioavailable to D. rerio embryos directly exposed to sediments and that the induction of specific genes can be used as biomarkers for the exposure of early life stages of zebrafish to metal-contaminated sediments.

Prospective study of immunologic effects of hydralazine in hypertensive patients.

Twenty-seven hypertensive patients (23 of whom were black) were treated with hydralazine as their major antihypertensive drug and were followed for evidence of autoimmunity and clinical systemic lupus erythematosus (SLE). Only one patient developed SLE but many, although asymptomatic, had serologic evidence of autoimmunity: antibodies to single- and double-stranded ribonucleic acid (RNA), single-stranded deoxyribonucleic acid (DNA), histones, and lymphocytes. Acetylation phenotype profoundly influenced this response; slow acetylators had a higher incidence and larger amounts of autoantibodies. Antibodies to both types of RNA were a more sensitive index of autoimmunity than antinuclear antibodies. Hydralazine treatment did not alter cell-mediated immune responses. The hydralazine SLE patient had large amounts of autoantibodies that were predominantly IgG, while in the others IgM autoantibodies were predominant. No antibodies, but positive lymphoproliferative responses to hydralazine, were found in half the patients tested.

3-Hydroxymethyl-s-triazolo[3,4-a]phthalazine, a novel urinary hydralazine metabolite in man.

The elucidation of the structure of a new major metabolic product of hydralazine, 3-hydroxymethyl-s-triazolo[3,4-a]-phthalazine, is described. The structures of several other previously described metabolites of the drug, phthalazone, s-triazolo[3,4-a]phthalazine, and 3-methyl-s-triazolo[3,4-a]phthalazine, are confirmed. A metabolic pathway of hydralazine is also proposed.

Vernix caseosa peritonitis. An infrequent complication of cesarean section with distinctive histopathologic features.

The authors report two cases of vernix caseosa peritonitis, an infrequent complication of cesarean section with distinctive histopathologic findings. Both patients underwent exploratory laparotomy for unexplained abdominal pain after cesarean section. Histopathologic evaluation of surgically removed tissue revealed an organizing peritonitis, which included prominent collections of anucleate squamous cells in association with a foreign body-type granulomatous response. In both cases, the surgical pathologist suggested that the abdominal pain was likely a result of peritoneal reaction to spillage of keratinous material (vernix caseosa) derived from amniotic fluid contents during cesarean section. Surgical pathologists should be aware of this entity and include it in the differential diagnosis of acute abdominal pain.

Electrochemistry and detection of some organic and biological molecules at conducting poly(3-methylthiophene) electrodes.

Electrodes modified by the electrodeposition of poly(3-methylthiophene) were used as chemical sensors for some organic and biological molecules of industrial and medicinal interest. The electrochemical behaviors of ferri/ferrocyanide, catechol, ascorbic acid, hydroquinone, dopamine epinephrine, acetaminophen, p-aminophenol and NADH were examined by cyclic voltammetry. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Differential pulse and square wave techniques were used for the analysis of binary mixture of ascorbic acid with catechol, NADH, dopamine and p-aminophenol. Voltammetric peak resolution was also demonstrated for a ternary mixture of ascorbic acid, catechol and p-aminophenol. Polymer coated electrode was also used in an amperometric detector for flow injection analysis of most of the aforementioned compounds. The responses of the polymer electrode were 4-10 times larger as compared to those of platinum. The modified electrode displayed excellent response stability for successive injections and detection limits were 10 ppb for catechol, dopamine, epinephrine, NADH and p-aminophenol, 1 ppb for acetaminophen and 100 ppb for ascorbic acid. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, film thicknesses were shown to be a factor affecting both the current magnitudes and oxidation peak potential of NADH.

Poly(binaphthyl-20-crown-6) as receptor based molecular selective potentiometric electrodes for catecholamines and other 1,2-dihydroxybenzene derivatives.

A novel type of poly(crown ether) electrode that is capable of selectively determining some 1,2-dihydroxybenzenes has been developed. A lipophilic macrocyclic crown ether, binaphthyl-20-crown-6, is electrochemically deposited on a platinum disc electrode. The film obtained is used as a sensory element for a potentiometric electrode for the determination of some neurotransmitters, namely, catecholamines. The new electrode is also capable of discriminating the steric shapes of 1,2-dihydroxybenzene moieties. The response of the new electrode is based on the principle of 'host-guest' chemistry. The potentiometric response is dependent on the pH of the solution and the nature of the buffer medium. The new sensor electrode has a useful analytical range of 1.5 x 10(-8) M-2 x 10(-5) M with a linear dynamic range between about 1 x 10(-7) M-5 x 10(-4) M with a 'super-Nernstian' slope of 110-130 mV/decade. The detection limit in phosphate buffer (0.1 M, pH 9.4) is ca. 3 x 10(-8) M for catecholamine. The sensor electrode is virtually insensitive towards interference from most inorganic ions and circumvents the interference from ascorbic acid, which is often found using amperometric methods in biological samples. A partial response mechanism of the present electrode is discussed, supported by results of electron dispersive analysis by x-rays (EDAX).

Functional responses of the left and right heart of diabetic rats to alpha- and beta-adrenergic receptor stimulation.

It was the aim of the present study to examine the influence of alpha-and beta-receptor stimulation on the function of the right (RV) and left (LV) ventricle of streptozotocin-diabetic rats (STZ; 60 mg.kg-1; n = 14). Phenylephrine (PE; 3 mg.kg-1.h-1) or isoproterenol (ISO; 24 micrograms.kg-1.h-1) were infused intravenously for 20 min 4 weeks after STZ injection. The hemodynamic parameters were measured on intact, anaesthetized animals with special Millar ultraminiature tipcatheter manometers. In the non-diabetic animals (n = 15), PE caused a significant elevation of left ventricular systolic pressure (LVSP) from 138.5 +/- 3.2 to 205.4 +/- 7.5 mmHg and raised heart rate (HR) from 362 +/- 12.6 to 399 +/- 17.2 beats.min-1 (mean +/- S.E.M.; P < 0.05). LVSP and HR were significantly lower in the diabetic animals under control conditions (110.5 +/- 6.4 mmHg and 273 +/- 16.0 beats.min-1, respectively) and not affected by PE. ISO induced a significant and comparable decrease in diastolic aortic pressure (DAP) and an increase in HR in both the non-diabetic and diabetic group. The PE-induced enhancements of LV dP/dtmax and RV dP/dtmax from 10533 +/- 805 to 21533 +/- 1386 and from 2044 +/- 262 to 3867 +/- 733 mmHg.s-1 were significant in the control animals. In the diabetic rats, LV dP/dtmax was lower (5971 +/- 901 mmHg.s-1) and was increased by PE to the range of control rats (11171 +/- 1591 mmHg.s-1). The PE-induced elevation of RV dP/dtmax from 2028 +/- 284 to 2771 +/- 391 mmHg.s-1 was less pronounced in the diabetic rats than in the controls. Under the influence of ISO, the increase of dP/dtmax in both ventricles was comparable to the effect of PE and fully preserved in the diabetic animals. Right ventricular systolic pressure (RVSP) was increased under PE and ISO in both groups to comparable values. These results demonstrate that the in vivo response to beta-adrenoceptor stimulation is well preserved in the diabetic rat, while the effects of alpha-stimulation are markedly reduced, especially in the left ventricle and systemic circulation.