Relation between nocturnal decline in blood pressure and mortality. The Ohasama Study

To investigate the relation between nocturnal decline in blood pressure and mortality, we obtained ambulatory blood pressures in 1542 residents aged 40 years or over of a rural Japanese community. Subjects were followed-up for a mean of 5.1 years and were then subdivided into four groups according to the percent decline in nocturnal blood pressure: 1) extreme dippers: percent decline in nocturnal blood pressure > or = 20% of the daytime blood pressure; 2) dippers: decline of > or = 10% but < 20%; 3) nondippers: decline of > or = 0% but < 10%; and 4) inverted dippers: no decline. The relationship between the decline in nocturnal blood pressure and mortality was examined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, previous history of cardiovascular disease, and the use of antihypertensive medication. The mortality risk was highest in inverted dippers, followed by nondippers. There was no difference in mortality between extreme dippers and dippers. This relationship was observed for both treated and untreated subjects, was more pronounced for cardiovascular than for noncardiovascular mortality, and did not change after the data were adjusted for 24-h, daytime, and nighttime blood pressure levels.

Factors that affect blood pressure variability. A community-based study in Ohasama, Japan

Factors that affect blood pressure (BP) variability, ie, standard deviation (SD) and variation coefficient (VC: SD/average ambulatory BP) of ambulatory BP, were examined in a community-based sample in northeastern Japan. Screening and ambulatory BPs were measured in 823 subjects > or = 20 years of age, and the effects of age and BP on the SD and the VC were examined. In bivariate regression analysis, the SD of ambulatory BP was positively correlated with age and the ambulatory BP. The VC was also correlated with age. Both the SD and the VC were strongly correlated with the magnitude of the nocturnal decline in BP. Ambulatory BP was positively correlated with age and negatively correlated with heart rate and the SD of heart rate. Multivariate analysis demonstrated that the nocturnal decline in BP showed the strongest association with the SD and the VC of 24-h BP. However, age and BP were still independently and positively associated with the SD and the VC of ambulatory BP. Furthermore, pulse pressure and BMI were independently and positively associated with the SD and the VC of ambulatory BP. Since the SD and the VC of 24-h ambulatory BP were determined mainly by the nocturnal decline in BP, this variable appears to be an index of the circadian variation in BP and not an index of short-term BP variability. Pulse pressure, an index of arterial stiffness, was a relatively strong predictor of the SD and the VC of BP. In addition, the SD of heart rate, an index of baroreflex function, decreased with increasing age. Findings suggest that the increase in BP variability in hypertensive and elderly subjects may be explained, in part, by a disturbance of baroreflex function associated with an increase in arterial stiffness due to aging and hypertension.

Reproducibility of home blood pressure measurements over a 1-year period

We compared the reproducibility over time of blood pressure measured at the health examinations (screening blood pressure) and blood pressure measured at home (home blood pressure). Both screening and home blood pressure were measured in subjects of a rural community. Subjects measured their own blood pressure at home once in the morning using a semiautomatic oscillometric blood pressure measuring device at least three times (on at least 3 days) in each of two 4-week periods separated by one year. Similarly, two screening blood pressure measurements were obtained from the subjects at each of two health examinations also taken 1 year apart. A total of 136 untreated subjects without cardiovascular complications (40 men and 96 women, 56 +/- 11.7 years, mean +/- SD) were analyzed in the study. The correlations between the first and second blood pressure measurements of the subjects were significantly higher for the home blood pressure measurements (systolic: r = 0.844 and diastolic: r = 0.830) than for the screening blood pressure measurements (systolic: r = 0.692 and diastolic: r = 0.570). The mean differences between the first and second home blood pressure (0.8 +/- 7.7 mm Hg for systolic BP and 0.9 +/- 5.5 mm Hg for diastolic BP) were significantly smaller than those for the screening blood pressure (-3.9 +/- 13.8 for systolic BP and -3.1 +/- 10.2 for diastolic BP) (P < .001 for both comparisons), suggesting that the reproducibility of home blood pressure over time is superior to that of screening blood pressure. Such reliable blood pressure measurements obtained at home have a clinical significance for the diagnosis and treatment of hypertension and as a tool for evaluating the efficacy of antihypertensive drugs. Home blood pressure measurements also may be more useful than screening blood pressure measurements in predicting future cardiovascular events.

Proposal of reference values for home blood pressure measurement: prognostic criteria based on a prospective observation of the general population in Ohasama, Japan

The purpose of this study was to propose reference values, from a viewpoint of prognostic significance, for blood pressure (BP) measured at home with a semiautomated device (home BP measurement) to differentiate normotension and hypertension. We obtained home BP measurements for 1,913 population-based subjects aged 40 years and over in a rural Japanese community and followed up their survival for a mean duration of 5.0 years. There were 141 deaths during the follow-up period. The association between baseline BP values and the overall mortality was examined by Cox proportional hazards regression model, adjusted for age, gender, and the use of antihypertensive medication. The results indicated that the predictive power of home BP level for subsequent mortality was stronger than that of casual screening BP. There was a linear association between home systolic BP and mortality. The association between home diastolic BP and mortality was nonlinear and well approximated with the secondary degree equation of diastolic BP values. Based on this relation, we propose that the reference value for hypertension is 137/84 mm Hg, and normotension is below 137 mm Hg for home systolic BP and between 66 and 83 mm Hg for home diastolic BP. Home diastolic BP below 66 mm Hg should be considered as low diastolic blood pressure. In this population, home systolic BP of 137 mm Hg and home diastolic BP of 84 mm Hg corresponded to the 80th and 87th percentiles, respectively. Then, 29% of the subjects were classified as having hypertension, 52% as normotension, and 19% as low diastolic blood pressure. All previous studies proposing reference values for home BP measurement, derived from cross-sectional observations, were based on the statistical distribution of home BP values. The reference value must, however, be the one that best predicts the risk for morbidity and mortality from hypertension-related complications. This is the first report proposing reference values for home BP measurement based on prognostic criteria.

Stage-specific cell-cycling of hematopoietic progenitor cells

We studied the growth of hematopoietic progenitors at different progressive stages of differentiation and focused especially on changes in cell-cycling. Hematopoietic progenitors from 5-fluorouracil (5-FU)-treated mice were separated into three groups on the basis of differentiation, Stages I, II, and III, and have studied their cell-cycling. Primary marrow cells collected from 5-FU-treated mice were categorized as Stage I progenitors. Stages II and III progenitors are early and late progenies of Stage I progenitors, respectively. The rate of growth of hematopoietic progenitors supported by interleukin-3 (IL-3) and steel factor (SF) was estimated by sequential analysis of colony formation and studying replating efficiency of individual colonies. The time required for hematopoietic progenitors to go through the cell-cycle shortened as their stage of differentiation progressed. Similar results were obtained with other growth factor combinations. The analysis of DNA content of cells suggests that shortening of cell-cycling is mainly due to a decrease in the time of G1 phase of the cell-cycle. Our results demonstrate that in early hematopoiesis, the cell-cycling of hematopoietic progenitors accelerates as they differentiate.

Two components of transmitter release in retinal bipolar cells: exocytosis and mobilization of synaptic vesicles

Ca2+-transmitter release coupling was examined using bipolar cells with large presynaptic terminals dissociated from the goldfish retina. Presynaptic Ca2+ current (I(Ca)) was recorded under the whole-cell voltage clamp. Release of excitatory amino acid transmitter was simultaneously monitored as the current through N-methyl-D-asperate (NMDA) receptors of reporter cells or as the membrane capacitance (C(m)) change associated with exocytosis. When I(Ca) was activated by a long depolarizing pulse, a double-peaked transmitter-induced current (I(tr)) was elicited in reporter cells. The rapid component of I(tr) was evoked immediately after the onset of depolarization, and was affected only slightly by intracellularly applied Ca2+ chelators. The delayed slow component of I(tr) was elicited during depolarization once a fixed amount of Ca2+ was accumulated in presynaptic terminals, and its appearance was suppressed or retarded by Ca2+ chelators. Two components of transmitter release were also recognized by monitoring C(m) changes elicited by the activation of I(Ca). These results suggest that bipolar cells have at least two pools of synaptic vesicles; a small, immediately releasable pool and a large releasable pool. The rapid and the delayed slow components of transmitter release may reflect exocytosis and mobilization of synaptic vesicles, respectively.

Role of nitric oxide in the development of vascular alpha 1-adrenoreceptor desensitization and pressure diuresis in conscious rats

We evaluated whether a minor impairment of the L-arginine-nitric oxide pathway would affect the desensitization of vascular alpha-adrenoreceptor and pressure diuresis induced by prolonged intravenous infusion of phenylephrine (an alpha-adrenoreceptor agonist) in conscious Wistar-Kyoto rats. We examined dose-pressor-response curves to phenylephrine after an intravenous infusion of phenylephrine (2.5 micrograms.kg-1.min-1) or saline for 9 hours with and without concomitant infusion of N omega-L-arginine methyl ester (L-NAME) given to partially inhibit the L-arginine-nitric oxide pathway. In addition, to evaluate the effect of plasma volume loss on the pressor response to phenylephrine, we evaluated the dose-pressor-response curves to phenylephrine after intravenous injection of furosemide (5 mg/kg) or infusion of phenylephrine (5 micrograms.kg-1.min-1) for 9 hours. The renin-angiotensin, vasopressin and autonomic nervous systems were blocked before the examination of dose-pressor responses. Prolonged infusion of phenylephrine (2.5 micrograms.kg-1.min-1) shifted the dose pressor-response curve to this agent rightward, with significantly increased log ED50 (the dose needed to reach 50% of the maximal response) to a similar extent in both L-NAME-treated (0.51 +/- 0.05 versus 0.93 +/- 0.07 microgram/kg) and -untreated (0.79 +/- 0.06 versus 1.08 +/- 0.03 micrograms/kg) rats. The log ED50 value after phenylephrine infusion (5 micrograms.kg-1.min-1) was significantly higher than that after furosemide injection (1.28 +/- 0.06 versus 1.02 +/- 0.01 micrograms/kg, respectively, P < .01), although the two treatments induced a similar loss of plasma volume. The slope in the linear relationship between the average change in mean arterial pressure during the 9-hour infusion period and the rate of urine excretion was significantly depressed in L-NAME-treated versus control rats (L-NAME: 0.057 mL.kg-1.h-1.mm Hg-1, control: 0.146 mL.kg-1.h-1.mm Hg-1, P < .05). In conclusion, a minor impairment of the L-arginine-nitric oxide pathway does not appear to interfere with the desensitization of vascular alpha-adrenoreceptor but does inhibit the pressure-diuresis response in conscious normotensive rats.

Prediction of mortality by ambulatory blood pressure monitoring versus screening blood pressure measurements: a pilot study in Ohasama

OBJECTIVE

To compare the prediction of mortality by ambulatory blood pressure monitoring and screening blood pressure measurements in a general population.

DESIGN

A prospective cohort study.

PATIENTS AND METHODS

We obtained blood pressure data for 1542 subjects (565 men and 977 women) aged > or = 40 years who were followed up for up to 8.1 years (mean 5.1 years). Subjects were subdivided into five groups according to their ambulatory and screening blood pressure levels. The prognostic significance of blood pressure for mortality was examined by the Cox proportional hazards regression model.

RESULTS

The association between blood pressure level and mortality was more distinctive for the ambulatory blood pressure than it was for the screening blood pressure. The risk of cardiovascular mortality increased significantly for the highest quintiles of 24 h ambulatory blood pressure, whereas there was no significant association between the screening blood pressure and the cardiovascular mortality. When both 24 h and screening blood pressure values were included in the Cox model, only the systolic ambulatory blood pressure was related significantly to the increased risk of cardiovascular mortality.

CONCLUSIONS

The ambulatory blood pressure had a stronger predictive power for mortality than did the screening blood pressure. This appears to have been the first study of the prognostic significance of ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population.

Cytotoxic fragment of amyloid precursor protein accumulates in hippocampus after global forebrain ischemia

We developed an antibody specific to beta-amyloid precursor protein (beta APP) fragments possessing the exact amino terminus of the beta-amyloid peptide and examined its induction in postischemic hippocampus. In control hippocampus, this APP fragment was lightly observed in pyramidal neurons of CA sectors and dentate granule cells. Transient forebrain ischemia enhanced accumulation of the APP fragment in CA1 pyramidal neurons. Seven days after the ischemia, while the APP fragment was still observed in dentate granule cells and CA3 neurons, it disappeared in dead CA1 neurons. While astrocytes did not show in any immunoreactivity throughout the experiment, those in the CA1 sector showed moderate immunoreactivity 7 days after the ischemia. The APP fragment has a cytotoxic effect on cultured neurons. These results suggest that the accumulation of the cytotoxic APP fragment in CA1 neurons may play a role in the development of delayed neuronal death after the ischemic insult.

Studies on agents with vasodilator and beta-blocking activities. IV

A series of novel pyridazinone derivatives (II) having a phenoxypropanolamine moiety was synthesized. Their hypotensive and beta-blocking activities were evaluated after intravenous administration of the compounds to anesthetized rats. Among them, the 5-chloro-2-cyanophenoxy derivative (29) showed the promising dual activities and was selected for further studies.

Quantitative analysis of low molecular weight G-actin-binding proteins, cofilin, ADF and profilin, expressed in developing and degenerating chicken skeletal muscles

A large amount of G-actin is pooled in the cytoplasm of young embryonic skeletal muscle and, although its concentration is reduced as muscle develops, the total amount of actin in muscle cells increases remarkably. Three G-actin-binding proteins, cofilin, ADF and profilin, are known to be involved in creating the G-actin pool in the embryonic muscle. To better understand how they are responsible for the regulation of assembly and disassembly of actin in developing and degenerating muscles, we measured the amounts of the three G-actin-binding proteins by means of quantitative immunoblotting and compared them with that of G-actin. The sum of the amounts of the three actin-binding proteins was insufficient at early developmental stages but sufficient at later stages to account for the pool of G-actin in young muscle cells. It decreased in parallel with the decrease in the G-actin pool as muscle developed. Expression of thymosin beta 4, which is known to be extremely important for G-actin-sequestering in a variety of non-muscle cells, was detected at a considerable level in young embryonic but not in adult skeletal muscles according to Northern and Western blotting. In degenerating denervated and dystrophic muscles, cofilin and profilin, but not ADF, were significantly increased in amount. From these results, we conclude that the G-actin pool in young embryonic skeletal muscle is mainly due to cofilin, ADF, profilin and thymosin beta 4, but thymosin beta 4 as well as ADF becomes less important as muscle develops. Cofilin and profilin may also be involved in the redistribution of actin during myofibrillogenesis and in the process of actin disassembly in degenerating muscles.

Activity of the ligand for c-mpl, thrombopoietin, in early haemopoiesis

We examined the role of the ligand for c-mpl. thrombopoietin (TPO). in murine early haemopoiesis. using a serum-free culture system. TPO in combination with the ligand for c-kit (SF) or interleukin-3 (IL-3) supported colony formation by marrow cells of 5-fluorouracil (5-FU)-treated mice whereas TPO alone yielded no colony. When blast cell colonies grown in the presence of TPO plus SF or TPO plus IL-3 were individually replated in suspension cultures containing serum and several growth factors, various combinations of myeloid lineages were seen, indicating that the progenitors supported by TPO plus SF or TPO plus IL-3 are multipotential. Delayed addition experiments demonstrated that TPO has the potential to effectively support the survival of haemopoietic progenitors. We then studied the effects of TPO on proliferative kinetics of cycling progenitors. TPO hastened IL-3-dependent growth of progenitors by shortening the time required for cell cycling. These results suggest that TPO as a single factor, can support the survival of haemopoietic progenitors and TPO synergizes with SF or IL-3 to act on early multipotential haemopoietic progenitors.

Accelerated cell-cycling of hematopoietic progenitors by the flt3 ligand that is modulated by transforming growth factor-beta

Although hematopoietic growth factors have been extensively studied as to their roles in recruitment of hematopoietic progenitors from quiescence state to cell division state, little is known of their effects on cell-cycling of progenitors that have already transited from quiescence into active cell-cycling. We examined the effects of the flt3 ligand (FL) on cell-cycling of hematopoietic progenitors in serum-free culture. Results from our serial observations of colony formation and replating experiments suggest that FL enhances the rate of growth of interleukin-3 (IL-3)-dependent colonies by shortening the time for each progenitor in the colonies to divide. Cell-cycle analysis showed that shortening of cell-cycle time induced by FL is mainly because of alteration in the G1 phase that hematopoietic progenitors go through. We next investigated the role of transforming growth factor-beta (TGF-beta) in cell-cycling of progenitors, using TGF-beta protein and TGF-beta antisense oligonucleotides, because mRNA of TGF-beta was detected by reverse transcriptase polymerase reaction in blast cells that we used as a source of progenitors. TGF-beta lengthened the time required for IL-3-dependent progenitors to become two daughter cells, whereas the effects of TGF-beta antisense oligonucleotides were opposite to those of TGF-beta. The addition of TGF-beta neutralizing monoclonal antibodies to the cultures resulted in effects similar to those seen with TGF-beta antisense oligonucleotides. DNA studies indicated that both TBF-beta and TGF-beta antisense oligonucleotides change the length of G1 phase of the cell-cycle. TGF-beta abrogated the effects of FL on the growth rate of hematopoietic progenitors, whereas the combination of FL with TGF-beta antisense oligonucleotides exerted additive effects. These data show that FL has the potential to accelerate cell-cycling of hematopoietic progenitors, which is susceptible to the modulation by TGF-beta.

G-CSF accelerates the cell-cycling of hematopoietic progenitor cells and abrogates the deceleration by TNF alpha

We examined the effects of granulocyte colony-stimulating factor (G-CSF) on cell-cycling of hematopoietic progenitors in serum-free methylcellulose clonal cultures. Serial observations of the cultures showed hastening of growth of colonies by G-CSF, as determined by evaluating the time for individual colonies of 20 cells to reach 40 cells. G-CSF did not affect the incidence of proliferating cells in each developing colony. Cell-cycle analysis revealed that addition of G-CSF to cultures led to a decrease in the percentage of cells in the G1 phase of the cell-cycle, thereby indicating that G-CSF can modulate the cell-cycle of hematopoietic progenitors mainly by shortening the period of the G1 phase. Tumor necrosis factor alpha (TNF alpha) exerted opposite effects on cell-cycling of hematopoietic progenitors to those seen with G-CSF. G-CSF abolished the inhibitory effects of TNF alpha on the cell-cycling of hematopoietic progenitors. These observations indicate positive and negative regulatory roles of C-CSF and TNF alpha, respectively, and their interactions in the regulation of cell-cycling of hematopoietic progenitors.

Analysis of a nuclear localization signal of simian virus 40 major capsid protein Vp1

The nuclear localization signal of the major structural protein, Vp1, of simian virus 40 was further defined by mutagenesis. The targeting activity was examined in cells microinjected with SV-Vp1 variant viral DNAs bearing either an initiation codon mutation of the agnoprotein or mutations in the Vp1 coding sequence or microinjected with pSG5-Vp1 and pSG5-Vp1 mutant DNAs in which Vp1 or mutant Vp1 is expressed from simian virus 40 early promoter. The Vp1 nuclear localization signal functioned autonomously without agno-protein once the Vp1 protein was synthesized in the cytoplasm. The targeting activity was localized to the amino-terminal 19 residues. While replacement of cysteine 10 with glycine, alanine, or serine did not affect the activity, replacement of arginine 6 with glycine caused the cytoplasmic phenotype. When multiple mutations were introduced among residue 5, 6, 7, 16, 17, or 19, the targeting activity was found to reside in two clusters of basic residues, a cluster of lysine 5, arginine 6, and lysine 7 and a cluster of lysine 16, lysine 17, and lysine 19. The clusters are independently important for nuclear localization activity.

Role of vasopressin in neurocardiogenic responses to hemorrhage in conscious rats

Vasovagal reflexes, such as hypotension and bradycardia, are induced by rapid hemorrhage and mimic neurocardiogenic reflexes in mammals. We examined the role of vasopressin in the neurocardiogenic responses to mild, rapid hemorrhage (1 mL/100 g for 30 seconds) and severe hemorrhage (1 mL/100 g body wt for 30 seconds repeated three times at 11-minute intervals) in homozygous Brattleboro and Long-Evans rats. Mild, rapid hemorrhage induced severe bradycardia and hypotension only in Long-Evans rats. Exogenous vasopressin (1.85 pmol/kg per minute for 1 hour) restored both the bradycardic and hypotensive responses in Brattleboro rats. DDAVP, a vasopressin V2-receptor agonist (0.19 pmol/kg per minute for 24 hours), did not affect the cardiovascular responses to hemorrhage in Brattleboro rats, although it maintained urine production within normal limits. However, OPC-31260 (21.6 mumol/kg IV), a vasopressin V2-receptor antagonist, attenuated both the hypotensive and bradycardic responses to hemorrhage in Long-Evans rats. A vasopressin V1-receptor antagonist attenuated bradycardia and delayed the recovery of arterial pressure after hemorrhage but did not affect the hypotension that occurred immediately after hemorrhage in Long-Evans rats. Methylatropine also attenuated both the bradycardic and hypotensive responses induced by hemorrhage, but propranolol had no effect on the cardiovascular responses to hemorrhage in Long-Evans rats. The recovery of arterial pressure after repeated hemorrhage was less adequate in Brattleboro rats than in Long-Evans rats. Our results suggest that the neurocardiogenic responses to hemorrhage, especially hypotension, may be related to vasodilation induced by a V2-receptor-mediated mechanism and by the vagal reflex, both of which are substantiated by the existence of vasopressin. The coexistence of V1- and V2-receptor mechanisms may be necessary for the hypotensive response to hemorrhage. We found that a V2-receptor antagonist attenuated the hypotension mediated by the so-called neurocardiogenic reflex.

Hemostatic abnormalities and increased vascular endothelial cell markers in patients with red cell fragmentation syndrome induced by mitomycin C

We examined red cell fragmentation syndrome (RCFS) induced by mitomycin C (MMC) (13 patients), by thrombotic thrombocytopenic purpura (TTP) (17 patients), and by disseminated intravascular coagulation (DIC) (15 patients). Plasma cytokine levels were increased in the TTP and DIC patients, but not in those whose RCFS was induced by MMC, suggesting that the activation of the immune system plays an important role in the pathogenesis of RCFS due to TTP and DIC but did not in RCFS due to MMC. Plasma thrombomodulin, tissue type plasminogen activator, and plasminogen activator inhibitor-I levels were increased in all RCFS patients, suggesting that RCFS, whether MMC induced, or due to TTP or DIC, might be associated with vascular endothelial cell injury. In TTP, von Willebrand factor (vWF) antigen and high molecular weight vWF multimer levels were reduced, possibly as a result of microthrombus consumption. The hemostatic data in this study showed that the TTP patients were in a hypercoagulable state without hyperfibrinolysis, and that DIC patients were in both a hypercoagulable and a hyperfibrinolytic state, whereas hemostatic abnormalities were slight in patients with MMC induced RCFS. These findings suggest that vascular endothelial cell injuries might be associated with RCFS, and that those injuries in MMC-induced RCFS might not be related to microthrombi or an activated immune system.

Activity of smooth muscle phosphatases 1 and 2A in rabbit basilar artery in vasospasm

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage frequently leads to a long-term cerebral artery narrowing called vasospasm. Recently, the involvement of myosin light chain kinase has been found in experimental vasospasm in our laboratory. We therefore measured the activity of serine/threonine protein phosphatases 1 and 2A in the rabbit basilar artery in vasospasm and in vasocontraction to study their role, particularly in regard to vasospasm compared with vasocontraction.

METHODS

Vasospasm was produced in the rabbit basilar artery by a two-hemorrhage method. Vasocontraction was induced by local application of KCl or serotonin to the rabbit basilar artery after a transclival exposure. The control animals were treated with saline instead of fresh blood. Serine/threonine protein phosphatase activity in the basilar artery was assayed with the use of [32P]phosphorylase-a as a substrate; protein phosphatase 1 activity was evaluated as protein phosphatase activity in the presence of 1 nmol/L okadaic acid, whereas protein phosphatase 2A activity was assessed as protein phosphatase activity inhibited by 1 nmol/L okadaic acid.

RESULTS

Values of mean activity of protein phosphatase 1 in myofibrillar extract were 3.58 +/- 0.26 nmol/min per milligram in the control group, 3.22 +/- 0.12 nmol/min per milligram in the spastic group on day 2, and 3.01 +/- 0.16 nmol/min per milligram in the spastic group on day 4 (a significant decrease in protein phosphatase 1 activity in the spastic group on days 2 and 4). In contrast, these values did not show any significant changes in the KCl and serotonin groups. Values of mean activity of protein phosphatase 2A in cytosolic extract were 0.90 +/- 0.07 nmol/min per milligram in the control group, 0.75 +/- 0.10 nmol/min per milligram in the spastic group on day 2, and 0.62 +/- 0.17 nmol/min per milligram in the spastic group on day 4 (a significant reduction in protein phosphatase 2A in the spastic group on days 2 and 4). There was no evidence of significant changes of protein phosphatase 2A in cytosolic extract in the KCl and serotonin groups.

CONCLUSIONS

Protein phosphatase 1 in myofibrillar extract is reported to catalyze the dephosphorylation of myosin light chain and calponin, whereas protein phosphatase 2A in cytosolic extract catalyzes the dephosphorylation of calponin and caldesmon. In addition, the phosphorylation of calponin and caldesmon results in the loss of their ability to inhibit smooth muscle contraction. Therefore, the significant decrease in activity of protein phosphatases 1 and 2A in vasospasm may result in uninterrupted vascular smooth muscle contraction by the preservation of phosphorylation of not only myosin light chain but also calponin and caldesmon.

Effects of vasopressin V1 and V2 receptor antagonists on the development of salt-induced hypertension in Dahl rats

To determine whether the vasopressor and antidiuretic actions of arginine vasopressin (AVP) may participate in the development of salt-induced hypertension, we examined the long-term effects of AVP V1 and V2 receptor antagonists on blood pressure (BP) in Dahl-Iwai salt-sensitive (DS) and salt-resistant (DR) rats. From age 7 weeks, DS and DR rats were fed a diet containing 8% NaCl, alone (control group); 8% NaCl and 1% OPC-21268 (V1 antagonist-treated group); or 8% NaCl and 0.05% OPC-31260 (V2 antagonist-treated group). The pressor response to AVP was significantly inhibited in DS rats treated with OPC-21268. Urinary volume and water intake were significantly increased by administration of OPC-31260; this increase was greater in DR rats than in DS rats. Indirect BP measurements obtained using tailcuff plethysmography showed that DS but not DR rats developed hypertension when fed high-salt diets. However, chronic treatment with either OPC-21268 or OPC-31260 did not alter the course of hypertension in DS rats, despite the effective blocking actions of these antagonists. This finding also was confirmed by direct BP measurements. Our results indicate that even if AVP plays a role in salt-induced hypertension peripheral blockade of either subtype of AVP receptors does not prevent the development of hypertension in DS rats.

Synthesis of a novel dual inhibitor of thromboxane A2 synthetase and 5-lipoxygenase (E3040) via the direct coupling reaction of hydroquinone with 3-pyridinecarboxaldehyde

Synthesis of a novel dual inhibitor of thromboxane A2 synthetase and 5-lipoxygenase, 5,7-dimethyl-6-hydroxy-2-methylamino-4-(3- pyridylmethyl)benzothiazole (E3040), was accomplished via a new coupling reaction, in which a key intermediate, (3,6-dihydroxy-2,4-dimethylphenyl)-(3-pyridyl)methanol, was easily synthesized in a high yield from 2,6-dimethyl-1,4-benzohydroquinone and 3-pyridinecarboxaldehyde in 6 N hydrochloric acid. The regio isomers of 3-pyridinecarboxaldehyde also gave the corresponding coupling products in high yields.

The role of nitric oxide in the baroreceptor-cardiac reflex in conscious Wistar rats

The role of nitric oxide (NO) in baroreceptor-cardiac reflex function was examined using a NO synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME), in conscious Wistar rats. Mean arterial pressure (MAP) and heart period (HP) relationships were obtained by intravenous injection of graded doses of phenylephrine and sodium nitroprusside (SNP). The baroreflex function was compared before and after L-NAME (10 mg/kg iv), L-NAME (10 mg/kg iv) followed by exogenous NO supplied as SNP (10-20 micrograms.kg-1.min-1 iv), or SNP alone (20 micrograms.kg-1.min-1 iv). To find the effect of changing basal MAP on baroreflex function, the baroreflex function was also examined before and after phenylephrine (8 micrograms.kg-1.min-1 iv) or L-NAME followed by concomitant infusion of SNP and phenylephrine. L-NAME increased basal MAP as well as HP from 104 +/- 1 to 141 +/- 2 mmHg and from 168 +/- 3 to 237 +/- 7 ms, respectively. L-NAME shifted the sigmoid curve in the direction of higher MAP with a significant increase in the gain (gain: control 2.14 +/- 0.15 ms/mmHg, L-NAME 3.70 +/- 0.26 ms/mmHg, P < 0.001). L-NAME together with SNP infusion did not significantly affect the gain, basal MAP, or HP. Infusion of SNP alone shifted the sigmoid curve in the direction of lower MAP but had no significant effect on the gain. An infusion of phenylephrine or L-NAME with concomitant infusion of SNP and phenylephrine increased basal MAP similarly as L-NAME alone did but had no significant effect on the gain.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of vascular nitric oxide to basal blood pressure in conscious spontaneously hypertensive rats and normotensive Wistar Kyoto rats

1. The aim of this study was to clarify the extent to which vascular nitric oxide contributes to basal blood pressure in conscious spontaneously hypertensive rats and normotensive Wistar Kyoto rats. 2. The contribution of vascular nitric oxide to maintenance of blood pressure was estimated by measuring the pressor response to an intravenous injection of nitric oxide synthase inhibitor, N omega-L-arginine methyl ester, given after serial injections of captopril, vasopressin V1-receptor antagonist (V1-antagonist) and ganglion blocker (pentolinium) in conscious spontaneously hypertensive and Wistar Kyoto rats aged 20-28 weeks. To estimate the 'amplifier property' of hypertrophied vasculature in spontaneously hypertensive rats, which is known to modulate pressor responses, the lower blood pressure plateau after serial injections of captopril, V1-antagonist and pentolinium and the maximum blood pressure elicited by subsequent injection of increasing doses of phenylephrine were also measured. 3. The serial injections of captopril, V1-antagonist and pentolinium decreased mean arterial pressure from 164 +/- 9 mmHg to 67 +/- 2 mmHg and from 117 +/- 2 mmHg to 49 +/- 1 mmHg in spontaneously hypertensive and Wistar Kyoto rats respectively. The subsequent injection of N omega-L-arginine methyl ester restored mean arterial pressure almost to its control levels in both spontaneously hypertensive and Wistar Kyoto rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Vesicular monoamine uptake by digitonin-permeabilized PC12 cells: inhibitory effect of neuromodulators and drugs on the amine transport

Vesicular amine transport is crucial for activity of monoaminergic neurons since translocation of cytosolic amine to storage vesicles is required for both exocytotic release and reuptake of the neurotransmitter. We developed a convenient assay system for vesicular amine transport based on permeabilizing the plasma membrane of pheochromocytoma PC12 cells with digitonin at concentrations of 100 to 150 microM. Serotonin (5HT) is a better substrate than either epinephrine or norepinephrine in this assay system. In the presence of 2 mM ATP, 5HT uptake by the permeabilized cells increased linearly for at least 30 min at 25 degrees C, whereas without addition of exogenous ATP, 5HT uptake reached an apparent plateau after 20 min incubation. Reserpine (500 nM) completely blocked the ATP-dependent 5HT uptake in this system whereas nomifensine (10 microM) had no effect, indicating specificity for vesicular transport. Treatment of intact PC12 cells with AMP dose-dependently decreased 5HT uptake with an EC50 of 20-30 microM as measured after cell permeabilization. Treatment of the intact PC12 cells with forskolin and phorbol 12-myristate 13-acetate prior to permeabilization also down-regulated vesicular 5HT transport, whereas the addition of either of these agents into the reaction mixture for the amine uptake by already permeabilized cells did not alter the vesicular uptake activity. Thus, the system can be applied to studies on regulation of the vesicular amine transport by physiological signaling molecules, intracellular messengers, and drugs.

Effects of protein kinase inhibitors and protein phosphatase inhibitors on cyclic AMP-dependent down-regulation of vesicular monoamine transport in pheochromocytoma PC12 cells

Cyclic AMP down-regulates vesicular monoamine transport in PC12 cells and thereby decreased catecholamine reuptake from the extracellular fluid. We examined the effects of protein kinase inhibitors and protein phosphatase inhibitors on this cAMP action. Treatment of cells with a protein kinase inhibitor, K252a, increased vesicular amine transport and cellular amine uptake, thereby antagonizing the regulatory action of cAMP. In contrast, a protein phosphatase inhibitor, okadaic acid, had the opposite effect on the amine transport, i.e. it enhanced the cAMP action. These results suggest the involvement of a protein phosphorylation process in the cAMP-dependent modulation of vesicular monoamine transport.