Hypertension Research
Online ISSN : 1348-4214
Print ISSN : 0916-9636
ISSN-L : 0916-9636
Volume 21 , Issue 3
Showing 1-13 articles out of 13 articles from the selected issue
  • Tomoya Hirayama, Yuji Ogawa, Katsuyuki Tobise, Kenjiro Kikuchi
    1998 Volume 21 Issue 3 Pages 137-145
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    Vasorelaxation induced by lysophosphatidylcholine (LPC) and platelet activating factor (PAF) was examined in rings isolated from rat aorta and mesenteric artery. LPC caused dose-dependent vasodilatation, which was sensitive to CV-6209, a PAF antagonist, and NG-monomethyl-L-arginine, a nitric oxide synthase inhibitor, but insensitive to indomethacin. PAF (10-7M) caused a tachyphylactic effect in mesenteric artery, but no tachyphylactic effect was demonstrated with LPC. Vasorelaxation patterns with LPC differed from those with PAF in the rat mesenteric artery. These results suggest that LPC-induced vasorelaxation may involve increased nitric oxide production mediated by the PAF receptor pathway, another receptor pathway possibly blocked by CV-6209, or PAF itself produced in endothelial cells in response to LPC. (Hypertens Res 1998; 21: 137-145)
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  • Pablo Prados, Tomofumi Santa, Takeshi Fukushima, Hiroshi Homma, Chieko ...
    1998 Volume 21 Issue 3 Pages 147-153
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    Nicardipine, a dihydropyridine type calcium channel blocker, was infused into 4-, 6-, and 23-wk-old spontaneously hypertensive (SH) and age-matched normotensive Wistar-Kyoto (WKY) rats (under sodium thiobutabarbital anesthesia and ventilation, n=4) through the left femoral vein, resulting in the reduction of blood pressure. In each rat, mean arterial blood pressure, heart rate, and the concentration of plasma catecholamines (CAs), norepinephrine (NE), and epinephrine (E) were concomitantly determined, and the correlations between these three variables were studied. During the infusion of nicardipine, the plasma concentration of CAs was measured with an automatic detection system in blood samples collected from the right femoral artery of each rat. The reduction in blood pressure induced by nicardipine brought about an increase in plasma CA levels. The blood pressure correlated well with the logarithm of plasma NE or E concentration according to the formula Y=-α log (X)+m (Y, blood pressure; X, concentration of plasma NE or E; α, slope; and m, intercept). The slopes (αs) of 6-wk-old and 23-wk-old SH rats were significantly greater than those of aged-matched WKY rats, meaning that the increment in plasma CAs in response to a decrease in blood pressure was smaller in SH than in WKY rats of similar ages. However, no significant differences were found between the αs of 4-wk-old SH and WKY rats. We conclude that the increment in the baroreflex-mediated sympathetic activity in response to a drop in blood pressure induced by nicardipine is similar or greater in prehypertensive SH than in normotensive WKY 4-wk-old rats, while the increment becomes smaller in SH rats with the onset of hypertension (6-wk-old rats), and is much less in fully hypertensive adult (23-wk-old) SH rats than in age-matched WKY rats. On the basis of these findings and previous data obtained by neurography, we conclude that plasma CAs can be used to evaluate baroreflex-mediated sympathetic activity countering the blood pressure reduction caused by calcium antagonists. (Hypertens Res 1998; 21: 147-153)
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  • Satoshi Yamaguchi, Kouichi Tamura, Nobuo Nyui, Kiyoshi Hibi, Tomoaki I ...
    1998 Volume 21 Issue 3 Pages 155-161
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We studied the localization of angiotensinogen mRNA in rat nephron segments and the differences in angiotensinogen mRNA levels between male Sprague-Dawley rats at 6 and 12wk of age using reverse transcription and polymerase chain reaction (RT-PCR). Each nephron segment of the rat kidney was microdissected. Total RNA was prepared and used in the following RT-PCR assay. The PCR products were size-fractionated by agarose gel electrophoresis, visualized with ethidium bromide staining, and identified by Southern blot analysis. The relative amounts of products were determined by densitometry. Strong bands corresponding to angiotensinogen mRNA were detected from proximal convoluted and straight tubules, and weaker bands were found in glomeruli. The signals in all tissues in 12-wk-old rats were weaker than those in 6-wk-old rats. Since local angiotensinogen is the unique substrate of the tissue renin-angiotensin system and exerts an autocrine-paracrine influence on renal function, the changes in tubular angiotensinogen may be related to physiological and morphological changes in the rat kidney during development. (Hypertens Res 1998; 21: 155-161)
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  • Koh-ichi Sugimoto, Akio Fujimura, Izumi Takasaki, Yasuo Tokita, Tamio ...
    1998 Volume 21 Issue 3 Pages 163-168
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We studied the effects of chronic blockade of the renin-angiotensin system on hypertension and cardiac left ventricular hypertrophy (LVH) in Dahl salt-sensitive (DS) rats given a high-salt or low-salt diet. [Experiment 1] Twelve-week-old male DS rats were fed an 8% NaCl diet and received the angiotensin II receptor (AT1) antagonist, candesartan (3mg/kg/d), the angiotensin converting enzyme inhibitor enalapril (30mg/kg/d), or vehicle for 6wk fter 3wk of 8% salt-loading. Neither candesartan nor enalapril with concomitant high salt-loading attenuated the blood pressure (BP) elevation. LVH was also not attenuated significantly by these treatments. [Experiment 2] After 8wk of 8% salt-loading, the rats were given a 0.3% NaCl diet and concurrently received candesartan, enalapril, or vehicle for 5wk. Switching from the high-salt to low-salt diet significantly decreased BP and left ventricular mass in the vehicle-treated animals. Both candesartan and enalapril normalized BP during salt-depletion; the blockade of the renin-angiotensin system produced an additive reduction in LVH. These findings suggest that sodium intak and hemodynamic load, but not the renin-angiotensin system, may be major determinants of the development of LVH in DS rats. (Hypertens Res; 21: 163-168)
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  • Yasushi Osaki, Kozo Matsubayashi, Masahiro Yamasaki, Kiyohito Okumiya, ...
    1998 Volume 21 Issue 3 Pages 169-173
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    To examine the clinical implications of post-stroke hypertension, defined as the rise in blood pressure on admission after the onset of ischemic stroke as compared with the blood pressure before stroke, and to assess the relationship between the value of post-stroke hypertension and neurologic recovery, we retrospectively studied 28 patients admitted to the hospital within 24h (mean±SD, 6.7±7.0h) after a firstever, acute non-embolic ischemic stroke, whose blood pressure had been recorded at the outpatient clinic within 3 mo before stroke. The Canadian Neurological Scale was used to assess stroke severity, and neurologic recovery during the acute phase was calculated. The average duration of hospitalization was 18±9d. The value of post-stroke hypertension and stroke severity on admission independently and significantly correlated with neurologic recovery (odds ratio, 1.06; 95% confidence interval, 1.00-1.12 and odd ratio, 0.20; 95% confidence interval, 0.06-0.72, respectively). There was also a significant linear correlation between the value of post-stroke hypertension and neurologic recovery (r= 0.50, p<0.01). Furthermore, blood pressure after the onset of ischemic stroke was quite independent of blood pressure before stroke. We conclude that the value of post-stroke hypertension correlates with neurologic recovery in patients with acute non-embolic ischemic stroke. These results suggest that blood pressure control mechanisms change after the onset of acute Ischemic stroke. (Hypertens Res 1998; 21: 169-173)
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  • Sohel R. Choudhury, Hirotsugu Ueshima, Akira Okayama, Yoshikuni Kita, ...
    1998 Volume 21 Issue 3 Pages 175-178
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    An association has been found between high blood pressure (BP) and the regular consumption of alcohol in epidemiological studies, and a repeated withdrawal reaction to alcohol is considered one of the mechanisms of high BP in drinkers. In this study, we investigated the association between BP and alcohol consumption on the previous day in regular male drinkers. The study participants were 551 men aged 20 to 59yr who drank alcohol regularly. BP was measured and information on daily alcohol intake was obtained from each participant by a questionnaire, which also asked whether alcohol had been consumed on the day before BP measurement. Age-adjusted BP was compared between participants who had (n=504, 91.6%) and those who had not (n=47, 8.4%) consumed alcohol on the previous day. There were no significant differences between the two groups with regard to BP or body mass index. Even after excluding subjects who were receiving anti-hypertensive drugs, there was still no significant difference in age-adjusted BP between the two groups. Our study found no association between BP and alcohol consumption on the previous day in regular male drinkers, which implies that alcohol withdrawal after 1d of abstinence cannot explain the high blood pressure found in regular drinkers in this Japanese middle-aged population. (Hypertens Res 1998; 21: 175-178)
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  • Hiroshi Kawamura, Hiromi Mitsubayashi, Tomoaki Saito, Katsuo Kanmatsus ...
    1998 Volume 21 Issue 3 Pages 179-186
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We studied ultradian and circadian variations in blood pressure (BP) in patients with essential hypertension who were receiving antihypertensive agents. No patient had previously received antihypertensive agents before this study began. After a 2-wk control period, we performed ambulatory blood pressure monitoring (ABPM) in 86 patients with essential hypertension (WHO stages I or II). The patients were then given a long-acting angiotensin converting enzyme inhibitor (ACEI) (captopril or imidapril), a β-receptor blocker (arotinolol or bisoprolol), or a calcium channel blocker (nisoldipine or benidipine) wice daily to control BP. We evaluated the patients' BP once every 2wk to ensure optimal control. After 12 wk, ultradian and circadian variations in BP were analyzed by the maximum entropy method (MEM). All antihypertensive agents decreased office systolic BP (SBP), office diastolic BP (DBP), 24-h SBP, and 24-h DBP. ACEI did not change office, 24-h, daytime, or nighttime pulse rate (PR). Arotinolol and bisoprolol decreased 24-h PR. All antihypertensive agents decreased 24-h, daytime, and nighttime pressure rate product. MEM showed that no antihypertensive agent affected the circadian variation in the 1st peak (24-h periodicity) of SBP, DBP, or PR. However, calcium channel blockers shortened the periodicity of circadian variations in the 2nd peak (12-h periodicity) of SBP and the 3rd peak (8 to 6h periodicity) of SBP. Therefore, ultradian variations in BP should be carefully monitored in hypertensive patients treated with calcium channel blockers. (Hypertens Res 1998; 21: 179-186)
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  • Katsuyuki Ando, Yasushi Ito, Mamoru Kumada, Toshiro Fujita
    1998 Volume 21 Issue 3 Pages 187-191
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We investigated the effect of oxidative stress on the expression of adrenomedullin (AM) mRNA in cultured rat vascular smooth muscle cells (VSMCs), using diethyldithiocarbamate (DDC), which is known to inhibit endogenous Cu, Zn superoxide dismutase (SOD) and to increase superoxide (O2-). DDC (10mM) increased O2- levels produced from rat VSMCs in a time-dependent fashion. Concomitantly, DDC increased the expression of AM mRNA for up to 24h, although it did not affect the expression of β-ctin mRNA. Thus, oxidative stress enhanced AM production in rat VSMCs, which may compensate for oxidative-stress-induced vasoconstriction. (Hypertens Res 1998; 21: 187-191)
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  • Tamaki Takada, Motoya Nakagawa, Nobuyuki Ura, Jun-ichi Kaide, Hideaki ...
    1998 Volume 21 Issue 3 Pages 193-199
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We evaluated the urinary excretion of immunoreactive endogenous ouabain-like factor (OLF) and digoxin-like factor (DLF) to investigate their pathophysiological roles in sodium metabolism and blood pressure in 5/6-reduced renal mass rats, a model of volume-expanded hypertension. About five-sixths of the kidney mass (5/6 RRM, n=9) was removed from male Sprague-Dawley rats, or the rats were sham operated (control, n=10). Both groups were fed regular diets with tap water for 1wk as a control period, followed by 1% saline solution for 4wk. Systolic blood pressure (SBP), urine volume (UV), urinary sodium excretion (UNaV), DLF, and OLF were measured on the last 2d of every week throughout the experimental period. SBP and UNaV were significantly higher in 5/6 RRM rats than in control rats. Urinary DLF significantly increased, reaching peak value in the first week, while OLF increased continuously, reaching peak value in the fourth week. In the first week, there were a significant positive correlations between the change in DLF and the changes in UNaV and SBP. However, the change in OLF was not correlated with changes in either UNaV or SBP. Both SBP and UNaV showed a significant positive correlation with OLF (p<0.001, r=0.547, p<0.001, r=0.658, respectively), whereas DLF significantly correlated with UNaV (p<0.001, r=0.584) but not with SBP in 5/6 RRM. These findings suggest that endogenous OLF and DLF coexist in rat urine and that an increased level of OLF, but not DLF, may contribute to the development and maintenance of hypertension. DLF may contribute to renal sodium excretion in this volume-expanded hypertensive rat model. (Hypertens Res 1998; 21: 193-199)
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  • Takao Kubo, Ryuji Fukumori, Midori Kobayashi, Hiroaki Yamaguchi
    1998 Volume 21 Issue 3 Pages 201-207
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    Cholinergic activities in the rostral ventrolateral medulla are enhanced in hypertensive animals, and enhanced cholinergic activity contributes to hypertension. Neurons in the lateral parabrachial nucleus and baroreceptors are suggested to be involved in mediation of acetylcholine release in the ostral ventrolateral medulla. To investigate the hypothesis that the lateral parabrachial nucleus is involved in the increased medullary cholinergic activity in hypertensive rats, we measured choline acetyltransferase activity in the rostral ventrolateral medulla, and examined effects of electrolytic lesioning of the lateral parabrachial nucleus in deoxycorticosterone acetate-salt hypertensive rats. We found that choline acetyltransferase activity in the medullary region was increased in deoxycorticosterone acetate-salt hypertensive rats. Unilateral lesioning of the lateral parabrachial nucleus abolished the increase in choline acetyltransferase activity in the lesioned side of the medullary region of hypertensive rats, whereas such activity in the medullary region of control rats was unaffected by lesioning. Bilateral lesioning of the lateral parabrachial nucleus inhibited the development of hypertension in hypertensive rats. In contrast, baroreceptor denervation did not inhibit the increase in choline acetyltransferase activity in the medullary region of hypertensive rats. These results are compatible with the hypothesis that the lateral parabrachial nucleus area is involved in mediation of increased medullary cholinergic activity and thus plays a role in the development of hypertension. (Hypertens Res 1998; 21: 201-207)
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  • Masahito Imanishi, Michiko Yano, Michiaki Okumura, Genjiro Kimura, Yuh ...
    1998 Volume 21 Issue 3 Pages 209-213
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    We previously proposed that aspirin can enhance the diagnostic sensitivity of renography with [123I] orthoiodohippurate (OIH) in patients with suspected unilateral renovascular hypertension (RVH). In this study we assessed the sensitivity and specificity of this method. Twenty-four patients, 14 with unilateral RVH and 10 with essential hypertension, were studied. For all patients with RVH, definitive diagnosis was based on the results of angiography and the response to renal arterial angioplasty after this study. For all patients with essential hypertension, we confirmed that there was little if any stenosis of the renal artery by digital subtraction angiography or Doppler sonography. Renography with [123I]OIH or 99mTc-mercaptoacetyltriglycine (MAG3) was done once before and once after the oral administration of aspirin (20mg/kg). We considered renal blood flow to be decreased if the time to the peak in renography was 5 min or more, and defined the peak times of the kidneys as different if eparated by 2min or more. Unilateral RVH was diagnosed when both criteria were met. Renography before aspirin administration indicated RVH in 7 of the 14 patients with RVH, and renography after aspirin indicated RVH in 13 of the 14 patients. Of the 10 patients with essential hypertension, renography before and after aspirin administration showed no difference between the kidneys in 8 patients. Thus, aspirin renography increased the sensitivity from 50% to 93%, but did not change the specificity (80%) in the diagnosis of RVH. These results suggest that renography with [123I]OIH or 99mTc-MAG3 for the diagnosis of unilateral RVH is more sensitive when aspirin is used. (Hypertens Res 1998; 21: 209-213)
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  • Junichi Minami, Toshihiko Ishimitsu, Teruo Higashi, Atsushi Numabe, Hi ...
    1998 Volume 21 Issue 3 Pages 215-219
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    Cilnidipine is a new and unique 1, 4-dihydropyridine calcium antagonist that has both L-type and N-type voltage-dependent calcium channel blocking actions. We compared the effects of cilnidipine and another once-daily dihydropyridine calcium antagonist, nisoldipine, on 24-h blood pressure and heart rate in patients with essential hypertension. We enrolled 10 hypertensive outpatients [9 men and 1 woman; age, 55 ±3 yr (means±SEM)] in this study. Their ambulatory blood pressure and heart rate were monitored for 24h at intervals of 30min with a portable recorder (TM-2425) after 8wk of treatment with ilnidipine (5 to 20mg once daily) and after 8wk of treatment with nisoldipine (5 to 20mg once daily). The order of the two treatments was randomized. Blood pressure and heart rate measurements for a 24-h period were analyzed for four segments of the day: morning (06:00 to 11:30), afternoon (12:00 to 17:30), nighttime (18:00 to 23:30), and sleeping time (0:00 to 5:30). Blood pressure levels were similar during the two treatment periods for each 6-h segment of the day. Heart rate was significantly higher during treatment with nisoldipine than during treatment with cilnidipine in the morning segment [by 4.1±1.3 beats/min (p<0.05)] and the afternoon segment [by 6.4±3.6 beats/min (p<0.05)]. These results suggest that cilnidipine is effective as a once-daily antihypertensive agent and causes reflex tachycardia less than does nisoldipine. (Hypertens Res 1998; 21: 215-219)
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  • Philippe M. Frossard, Gilles G. Lestringant, Yassin I. Elshahat, Anne ...
    1998 Volume 21 Issue 3 Pages 221-225
    Published: 1998
    Released: August 10, 2006
    JOURNALS FREE ACCESS
    As a key enzyme of the renin-angiotensin-aldosterone system, the renin gene (REN) is a good candidate quantitative trait locus that may be implicated in the molecular etiology of essential hypertension. Among mixed reports on the subject, a REN MboI restriction fragment length polymorphism has been shown to be significantly associated with a family history of hypertension in a Japanese population. We show here that the REN MboI dimorphic site is located in the ninth intron of the gene, and we describe a polymerase chain reaction-based assay for detection of this site. We investigated MboI genotype distributions in 331 hypertensive and 279 normotensive subjects from the United Arab Emirates (UAE), a genetically homogeneous ethnic population with no history of smoking or alcohol consumption. A statistically significant association was found between alleles on which the MboI site is present and clinical diagnosis of essential hypertension, indicating that 1) the presence of the MboI site is a marker for susceptibility to hypertension in the UAE (the associated odds ratio is 3.16); and 2) variations of the REN (or of a nearby) gene that may be in linkage disequilibrium with this marker play a role in the development of essential hypertension in the UAE. (Hypertens Res 1998; 21: 221-225)
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