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N Nyui

Publications and source records attributed to N Nyui.

28 records · Page 2Linked to original sources
PubMed1997

Distribution of alpha 1B-adrenergic receptor mRNA expression along rat nephron segments.

Although several alpha-adrenergic receptor genes are expressed in the rat kidney, little information is available on their expression in the renal nephron segments. We investigated the distribution of alpha 1B-adrenergic receptor mRNA in rat nephron segments using reverse transcription and polymerase chain reaction (RT-PCR). The nephron segments of six- to eight-week-old male Sprague-Dawley rats were microdissected. Total RNA was prepared by the acid-guanidinium-phenol-chloroform method and used in the following RT-PCR assay. The PCR products were size-fractionated with electrophoresis, visualized with ethidium bromide staining and confirmed by Southern blot analysis. Because the PCR primers spanned an intron, the amplification product of the predicted size was considered to be from alpha 1B-adrenergic receptor cDNA and not from genomic DNA. The PCR products were detected in glomerulus (Glm), proximal convoluted and straight tubules (PCT, PST) and cortical and medullary thick ascending limbs of Henle (CTAL, MTAL). No signals were detected in cortical or medullary collecting ducts (CCD, MCD). Large signals were detected in the PCT, and PST, while small signals were found in the Glm, CTAL and MTAL. The alpha 1B-adrenergic receptor mRNA was detected for the first time in rat Glm, PCT, PST and TAL using RT-PCR. alpha 1BAR mRNA seems to be expressed in the specific sites along the nephron and may play significant roles in renal functions, although the specific physiological effects of the renal alpha 1B-adrenergic receptor are unknown.

Animals↗
PubMed1997

Modulation of tissue angiotensinogen gene expression in genetically obese hypertensive rats.

Wistar fatty rats (WFR) show obesity and obesity-related features, including hypertension. In this study, we examined the expression of angiotensinogen mRNA in a variety of tissues at different times in WFR and control Wistar lean rats (WLR). WFR were obese and hypertensive at 16 and 24 wk. Plasma renin activity and plasma angiotensinogen concentration showed age-dependent increases in WFR but decreases in WLR. Northern blot analysis showed no significant differences in the levels of hepatic and renal angiotensinogen mRNA between WFR and WLR, and the levels of fat and adrenal angiotensinogen mRNA were lower in WFR than in WLR. On the other hand, the levels of cardiac angiotensinogen mRNA at 16 and 24 wk and those of aortic angiotensinogen mRNA at 16 wk were significantly higher in WFR than in WLR. These results show that the expression of tissue angiotensinogen mRNA is regulated differently in WFR and WLR and indicate that the development of hypertension in WFR is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as in cardiac and aortic angiotensinogen mRNA. Moreover, these results suggest the existence of obesity hypertension-linked and tissue-specific regulation of angiotensinogen gene expression.

Angiotensinogen↗
PubMed1997

Tissue angiotensinogen gene expression induced by lipopolysaccharide in hypertensive rats.

There is now convincing evidence that various tissues express their own tissue renin-angiotensin system, which may be regulated independently of the systemic renin-angiotensin system. However, little information is available on the regulation of the tissue renin-angiotensin system. We investigated the regulation of tissue angiotensinogen gene expression with respect to the development of hypertension. We measured basal and lipopolysaccharide-stimulated plasma angiotensinogen concentrations by radioimmunoassay and examined the expression of tissue angiotensinogen by Northern blot analysis in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at 4 and 13 weeks of age. Basal plasma angiotensinogen concentration in SHR was comparable to that in WKY at 4 weeks of age and was significantly higher than that in WKY at 13 weeks of age. Lipopolysaccharide induced a significant increase in plasma angiotensinogen concentration in both WKY and SHR at 4 and 13 weeks of age. At 4 weeks of age, the basal levels of angiotensinogen mRNA in the liver, fat, adrenal, and aorta were higher in WKY than in SHR. At 13 weeks of age, the basal levels of angiotensinogen mRNA in the fat, adrenal, aorta, spleen, and kidney were higher in WKY than in SHR, while that in the liver did not differ significantly between the two strains. At 4 weeks of age, pretreatment with lipopolysaccharide increased the angiotensinogen mRNA levels in the liver, fat, adrenal, and aorta in both WKY and SHR. At 13 weeks of age, pretreatment with lipopolysaccharide increased the angiotensinogen mRNA levels in the liver, aorta, and adrenal; decreased those in the spleen; and had no effect in the kidney in both WKY and SHR. Interestingly, lipopolysaccharide increased the angiotensinogen mRNA level in fat only in SHR, with no effect in WKY, at 13 weeks of age. Lipopolysaccharide stimulated tumor necrosis factor-a mRNA expression in fat of WKY and SHR, and the increase in tumor necrosis factor-alpha mRNA level in SHR was significantly greater than that in WKY. Therefore, the increased tumor necrosis factor-alpha mRNA expression may be involved in the increased lipopolysaccharide-induced expression of angiotensinogen gene in fat of SHR at 13 weeks of age. These data suggest that the transcriptional and probably posttranscriptional regulation of angiotensinogen mRNA differs between SHR and WKY, that the regulation of angiotensinogen gene expression is tissue-specific, and that the altered expression of the angiotensinogen gene may be involved in the development of hypertension.

Angiotensinogen↗
PubMed1997

Essential hypertension and 5' upstream core promoter region of human angiotensinogen gene.

The angiotensinogen (AGT) gene M235T variant is associated with essential hypertension and elevated plasma AGT concentrations, although the underlying mechanisms are unknown. Recent studies have suggested that AGCE 1 (human AGT gene core promoter element 1) located in the 5' upstream core promoter region (position -25 to -1) of the human AGT gene has an important part in the expression of AGT mRNA by binding with transcription factor AGCF 1 (human AGT gene core promoter element binding factor 1), and a mutation at -20 from adenine to cytosine (A-20C) increases the level of expression of this transcript. We therefore examined subjects with this mutation to study the association with increased plasma AGT concentrations and with essential hypertension. One hundred eighty-eight subjects receiving no antihypertensive medication were examined with regard to the correlation between A-20C and plasma AGT concentrations, and 234 subjects were studied with respect to the association between A-20C and essential hypertension. A-20C was determined by polymerase chain reaction-restriction fragment length polymorphism analysis with EcoOR 109I. Multiple regression analysis showed a weak but significant correlation between A-20C and plasma AGT concentrations (P=.047) and essential hypertension (P=.049). The results suggest that A-20C may underlie the increase in plasma AGT concentrations and be involved in the development of essential hypertension.

Angiotensinogen↗
PubMed1997

Analysis of molecular heterogeneity of Dahl/Iwai salt-sensitive rats and salt-resistant rats.

Molecular evidence, using DNA fingerprint analyses, of extensive genetic heterogeneity between spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) and even within some of the WKY colonies has been reported. Thus we investigated the genetic relations between Dahl S and R rats newly inbred by Dr. Iwai. Genomic DNA was isolated from the liver of four Dahl S and four Dahl R rats, digested with the restriction enzyme HinfI or AluI, and separated in 1.2% agarose gel by electrophoresis. Then, DNA fingerprinting was performed by Southern blot analysis using the human myoglobin 33.6 minisatellite probe. Bands were detected in an alkaline phosphatase reaction system. Within the same strains, there was no heterogeneity of these fingerprinting patterns. The S and R rats shared 82% of the bands in the HinfI-digested DNA and 93% of those in the AluI-digested DNA. These shared values were much greater than the reported value (54%) between SHR and WKY from Charles River Laboratories. These newly inbred Dahl S and R rats may be appropriate, although still limited, experimental animals for investigating the pathophysiology of salt-sensitive hypertension.

Animals↗
PubMed1997

Regulation of cardiac angiotensinogen mRNA in vivo and in vitro.

In this study, to investigate the mechanism of hypertension-associated induction of cardiac angiotensinogen in vivo and in vitro, we studied the regulation of angiotensinogen mRNA in the hearts of genetically hypertensive rats and in the rat cardiomyocytes. Levels of cardiac angiotensinogen mRNA were significantly increased in the hypertensive rats. Steady state mRNA levels for angiotensinogen mRNA in cardiomyocytes were increased by angiotensin II and mechanical stretch. The addition of an angiotensin II type 1 receptor antagonist (CV11974) and a transcriptional inhibitor (actinomycin D) completely blocked the induction of angiotensinogen mRNA by angiotensin II in cardiomyocytes. The addition of CV11974 significantly, but not completely, inhibited the induction of angiotensinogen mRNA by mechanical stretch. Actinomycin D completely blocked the induction of angiotensinogen mRNA by stretch in cardiomyocytes. An angiotensin II type 2 receptor antagonist (PD123319) and a protein synthesis inhibitor (cycloheximide) did not affect the induction. These results indicate that the expression of cardiac angiotensinogen mRNA is activated by the development of hypertensive cardiac hypertrophy, and that angiotensin II and mechanical stretch activates the angiotensinogen gene via the angiotensin II type 1 receptor-pathway in cardiomyocytes.

Angiotensinogen↗
PubMed1996

Tissue-specific regulation of angiotensinogen gene expression in spontaneously hypertensive rats.

Angiotensinogen is expressed in many tissues besides the liver. Recent studies have suggested that abnormalities in the regulation of angiotensinogen gene expression may be involved in the development of hypertension. However, little information is available concerning the functional significance of tissue angiotensinogen. In this study, we measured plasma angiotensinogen concentration by radioimmunoassay and examined the expression of tissue angiotensinogen by Northern blot analysis in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Although plasma angiotensinogen concentration in SHR was comparable to that in WKY at 6 weeks of age, it was increased significantly at 14 weeks of age in SHR and became higher than that in WKY. The levels of hepatic angiotensinogen mRNA were similar in SHR and WKY, and the levels of aortic, adrenal, and renal angiotensinogen mRNAs were lower in SHR than in WKY at both 6 and 14 weeks of age. Brain angiotensinogen expression in SHR was higher than in WKY at 6 weeks of age and was comparable to that in WKY at 14 weeks of age. On the other hand, cardiac and fat angiotensinogen mRNA levels were significantly increased at 14 weeks of age in SHR. These results demonstrate that the expression of tissue angiotensinogen is regulated differently in SHR and WKY and indicate that the development of hypertension is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as cardiac and adipogenic angiotensinogen mRNA in SHR.

Angiotensinogen↗
PubMed1995

Adenosine A1 receptor mRNA in microdissected rat nephron segments.

Adenosine plays several roles in the kidney mediated by the specific receptors A1, A2, and possibly A3. We studied the localization of adenosine A1 receptor mRNA in rat nephron segments using reverse transcription and polymerase chain reaction (RT-PCR). The nephron segments of male Sprague-Dawley rats (6 to 8 weeks old) were microdissected. Total RNA was prepared by the acid-guanidinium-phenol-chloroform method and used in the following RT-PCR assay. Because the PCR primers spanned no intron, samples reacted in the absence of RT were used as controls for amplification of genomic DNA. The PCR products were size-fractionated by electrophoresis, visualized with ethidium bromide staining, and confirmed by Southern blot analysis. PCR products were detected in all of the nephron segments examined. No signals were detected in samples reacted in the absence of RT. Strong signals were detected in glomeruli, medullary collecting duct, cortical thick ascending limb, and medullary thick ascending limb, while weak signals were found in proximal convoluted and straight tubules. Previously, the presence of A1 receptors has been demonstrated in glomeruli, collecting duct, and thick ascending limb in the rat kidney by autoradiography and binding studies. In addition to these segments, we further detected A1 receptor mRNA in proximal convoluted and straight tubules. Thus, A1 receptor mRNA seems to be broadly expressed along the nephron.

Animals↗
PubMedDate not supplied

Angiotensin II receptors in cardiac left ventricles of Dahl rats.

1. Dahl Iwai salt-sensitive (DS) rats have been reported as becoming hypertensive with left ventricular hypertrophy (LVH) and heart failure when on a high-salt diet. Their circulating renin-angiotensin system (RAS) has been reported to be suppressed. To evaluate the role of angiotensin II (AngII) type 1 and type 2 receptors (AT1 and AT2, respectively) in LVH, we compared cardiac AT1 and AT2 receptors in 10-week-old DS rats and Dahl Iwai salt-resistant (DR) rats. 2. Seven pairs of 6-week-old male DS and DR rats were fed either a low- or high-salt diet (0.3 or 8% NaCl, respectively) for 4 weeks. Left ventricular AngII receptors were measured by radioligand binding assays using [125I]-[Sar1,Ile8]-AngII in plasma membrane fractions from these four groups. The AT1 and AT2 receptors were distinguished using their specific antagonists CV 11974 and PD 123319, respectively. 3. The high-salt diet increased blood pressure and the left ventricle:bodyweight ratio in DS rats. However, neither Bmax for AT1 and AT2 receptors nor Kd for [125I]-[Sar1,Ile8]-AngII differed between the groups. These results are different from those of other reports of pressure-overload LVH, such as spontaneously hypertensive rats or renovascular hypertension rats, in which AT1 and AT2 receptors were reported to be up-regulated.

Animals↗