两肾两夹高血压与自发性高血压大鼠左心室肥厚的比较

目的 比较两肾两夹和自发性高血压大鼠左心室肥厚的异同.方法 采用不同周龄两肾两夹高血压和自发性高血压大鼠模型,测定动脉血压和心肌肥大指数, 超声心动图观察左心室结构和功能,左心室插管检测血流动力学指标.结果 不同周龄两肾两夹高血压和自发性高血压大鼠的血压及心肌肥大指数均显著高于周龄匹配的对照大鼠.与对照组相比,手术后4周的两肾两夹大鼠及8、12、16周龄的自发性高血压大鼠,其室间隔及左室后壁厚度均明显增加,左室内径显著减小,呈现出明显的向心性肥厚.而手术后8周及12周的两肾两夹大鼠,其室间隔及左室后壁厚度均明显减小,左室内径显著增大,呈明显的离心性肥厚.同时,手术后8周、12周的两肾两夹大鼠以及16周龄的自发性高血压大鼠,其射血分数、缩短分数、室内压最大上升和下降速率均较对照组显著降低,左室舒张末压及等容舒张期压力下降的时间常数明显升高.表明随时间延长,二者心功能都有不同程度的下降.结论 两肾两夹高血压和自发性高血压大鼠均发生了不同程度的左心室肥厚,但其肥厚表型不同.     

Proteomic identification of tyrosine nitration targets in kidney of spontaneously hypertensive rats

Nitrosative and oxidative stress are implicated in the development of hypertension. Events in the renal medulla may play a key role in the development and progression of hypertension. This may arise through disruption of nitric oxide signalling in the medulla and be accompanied by enhanced nitrosative and oxidative stress as indicated by the presence of proteins containing 3-nitrotyrosine. Here we demonstrate enhanced protein nitration in the medulla of spontaneously hypertensive rats. We have identified several nitrated proteins with both varied subcellular location and functional roles. These proteins are involved in nitric oxide signalling, antioxidant defense and energy metabolism. Moreover, increased nitration was observed in conjunction with enhanced oxidative damage as evidenced by the presence of protein carbonyl oxidative stress biomarkers. Our results suggest that kidney medulla is subject to enhanced nitrosative and oxidative stress, and that resulting protein modifications may contribute to the progression of hypertension.     

自发性高血压大鼠心肌和血管组织牛磺酸的转运障碍

在自发性高血压大鼠（SHR）的心肌和主动脉血管组织上观察牛磺酸（taurine)转运和牛磺酸转运体（taurine transporter,TAUT) mRNA 的改变,结果显示,与对照组WKY大鼠相比,SHR组血浆牛磺酸水平和牛磺酸释放量增加,而心肌和血管组织牛磺酸水平和TAUT mRNA含量均降低,牛磺酸最大转运速率（Vmax)分别低24％和35％（P＜0．05）,米氏常数（Km)值分别高16％和39％（P＜0．05）,这些结果提示,SHR的心肌和血管组织牛磺酸转运障碍可能与TAUT活性和亲和力降低及TAUT基因水平的下调有关。     

Properties of ventricular myocytes isolated from the hypertrophied and failing hearts of spontaneously hypertensive rats.

OBJECTIVE: To investigate how the morphological and physiological properties of single myocytes isolated from the hypertrophied, failing left ventricles (LV) differ from those of normal or hypertrophied not failing ventricles. METHOD: Single myocytes were isolated separately from right (RV) and left ventricles (LV) of male spontaneously hypertensive rats (SHR) or Wistar-Kyoto (WKY) rats at the age of 6 and 12 months and of SHRs which developed or not developed heart failure at the age of 20-24 months. We measured cells dimensions, range and kinetics of electrically stimulated or initiated by caffeine contractions and Ca2+ transients, and investigated the response of cells to thapsigargin. RESULTS: The transversal dimensions of the LV myocytes of 6 months old SHRs showed approximately 20% increase with respect to transversal dimensions of their RV myocytes and LV and RV myocytes of WKY rats. The difference did not change with progressing age and in the heart failure. The LV myocytes of 6 or 12 months old SHRs showed slowed kinetics of the Ca2+ transients and of contraction and relaxation and decreased contractile response to 2 s superfusion with 15 mM caffeine preceded by 5 mM Ni2+ used as an index of the sarcoplasmic reticulum (SR) Ca2+ content. Despite of this the range of shortening and relative contribution of the SR to contraction (assessed by measuring of the residual contractile response to electrical stimulation in cells poisoned with thapsigargin) or relaxation (assessed by calculation of the ratio of rate constants of the electrically stimulated and stimulated by 30 s superfusion with caffeine Ca2+ transients) was not altered in the hypertrophied myocytes. Properties of the LV myocytes of the 20-24 old SHRs with or without heart failure did not differ from those of LV myocytes of younger SHRs. The contractile response to caffeine of their RV myocytes dropped to the level of that in the LV myocytes. CONCLUSION: Our results suggest that transition from the compensated hypertrophy to the heart failure in 20-24 months old SHRs did not result from the further changes in properties of the surviving myocytes. Data from literature suggest that myocyte apoptosis and remodeling of the extramyocyte space is the more likely reason.     

Hyper-phosphorylation of alpha-enolase in hypertrophied left ventricle of spontaneously hypertensive rat

Cardiac hypertrophy is one of the main target organ damages of essential hypertension and predicts a poor prognosis of the disease. The molecules involved in this event, especially their posttranslational modifications, remain largely unknown to date. With a combination of phosphoprotein column enrichment and two-dimensional gel electrophoresis separation, here we compared the profiling of enriched phosphoproteins from the left ventricle (LV) of spontaneously hypertensive rats (SHR) to that of age-matched Wistar Kyoto rats. As a result, 19 differential proteins were found in the hypertrophied LV of SHR. Among them, we focused on a glycolysis enzyme α-enolase, of which the hyper-phosphorylation was shown in the hypertrophied LV but not in non-hypertrophied atrium and right ventricle of SHR. Furthermore, the α-enolase hyper-phosphorylation was accompanied by decreased enzymatic activity. The further investigation based on these results would provide new clues to understand the pathological process of cardiac hypertrophy in SHR.     

Proteomic identification of haptoglobin as a stroke plasma biomarker in spontaneously hypertensive stroke-prone rats

AIMS: We investigated changes in the expression of plasma proteins in spontaneously hypertensive stroke-prone rats (SHRSP) to identify stroke biomarkers. MAIN METHODS AND KEY FINDINGS: The present analysis using surface-enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF-MS) demonstrated that three peaks at mass/charge ratios (m/z) of 9330, 9480 and 9700 decreased in intensity during the development and progression of hypertensive stroke in SHRSPs, but not in age-matched control SHR and Wistar rats. Administration of verapamil, an L-type calcium channel blocker which was effective for hypertension in SHRSP rats, prevented the decrease in plasma protein expression. A candidate biomarker protein (m/z 9330) was identified using LC-MS/MS as haptoglobin (Hp). Immunoblotting with anti-Hp antibody demonstrated the decreased expression of both Hpalpha and Hpbeta chains in SHRSP. In contrast, haptoglobin mRNA expression in the liver of SHRSPs slightly increased as compared with control rats. SIGNIFICANCE: These findings suggest that Hp is a biomarker candidate for discriminating pathogenic alterations of stroke.     

Calpastatin level in spontaneously hypertensive rats

We studied calpastatin activity in erythrocytes of Milan hypertensive and prehypertensive rats, in their normotensive controls, in F1 and F2 hybrids, and in two inbred strains derived from F2, one hypertensive and the other normotensive. Our results show that the decrease in calpastatin activity observed in Milan hypertensive rats was not caused by hypertension, it was transmitted in a recessive way in heterozygous, and it was not correlated to hypertension.     

Interval bisection in spontaneously hypertensive rats

An interval bisection procedure was used to study time discrimination in spontaneously hypertensive rats (SHR), which have been proposed as an animal model for the attention deficit hyperactivity disorder (ADHD); Wistar Kyoto and Wistar rats were used as comparison groups. In this procedure, after subjects learn to make one response (S) following a short duration stimulus, and another (L) following a long duration stimulus, stimuli of intermediate durations are presented, and the percentage of L is calculated for each duration. A logistic function is fitted to these data, and different parameters that describe the time discrimination process are obtained. Four conditions, with different short and long durations (1-4, 2-8, 3-12, 4-16s) were used. The results indicate that time discrimination is not altered in SHR, given that no difference in any of the parameters obtained were significant. Given that temporal processing has been proposed as a fundamental factor in the development of the main symptoms of ADHD, and that deficits in time discrimination have been found in individuals with that disorder, the present results suggest the necessity of exploring time perception in SHR with other procedures and sensory modalities, in order to assess its validity as an animal model of ADHD.     

Plasma concentrations of endothelin-1 in spontaneously hypertensive rats and DOCA-salt hypertensive rats

To investigate the possible involvement of endothelin-1 (ET-1), an endothelium-derived potent vasoconstrictor peptide, in the pathophysiology of hypertension, plasma ET-1 levels in 15-week-old spontaneously hypertensive rats (SHR) and DOCA-salt hypertensive rats were measured with a sandwich-type enzyme immunoassay. The vasocontractile effect of ET-1 in aortic helical preparations was significantly more sensitive in DOCA-salt hypertensive rats than in control sham-operated rats, but plasma levels of ET-1 did not differ between them. Plasma ET-1 levels in genetically hypertensive rats (SHR and stroke-prone SHR) were significantly lower than those in age-matched normotensive Wistar-Kyoto (WKY) rats. The plasma concentrations of big ET-1, a precursor of ET-1, in both SHR and SHR-SP were significantly lower than those of WKY, suggesting that the production of ET-1 is decreased in rats of genetic hypertension. Although the vascular reactivity to ET-1 increased in both DOCA-salt hypertensive and genetically hypertensive rats, present findings of the plasma ET-1 levels suggest that the role of ET-1 in the vascular control system may be different in DOCA-salt hypertensive rats and genetically hypertensive rats.     

G-proteins in kidneys of spontaneously hypertensive rats

G(s alpha)-, total G(i alpha)- and G(q/11alpha)-protein concentrations were investigated by quantitative immunoblotting in membranes of total kidney, renal cortex and medulla as well as in cortical tubules and glomeruli of Spontaneously Hypertensive Rats (SHR) and normotensive Wistar Kyoto rats (WKY), aged 5 weeks, 3 or 8 months. We found that total kidney of 5 week old SHR possess less G(s alpha)-, G(i alpha)- and G(q/11alpha)-proteins than controls. For G(s alpha)-proteins, differences found in total kidney were mirrored both in cortex (tubules and glomeruli) and in medulla. Decreased G(i alpha)-concentrations were accompanied by lower tubular but higher glomerular levels, while medullar levels were also increased. Decreased G(q/11alpha)-concentrations were reflected in decreased glomerular and medullary concentrations. Kidneys of 3 month old SHR and WKY possessed similar concentrations of all G(alpha)-species. In 8 month old SHR similar G(i alpha)-, but decreased G(s alpha)-and G(q/11alpha)-concentrations were observed. The G(s alpha)-decrease was reflected in cortex and medulla, the G(q/11alpha)-decrease in the medulla. We conclude that the main strain-related differences in G(alpha)-concentrations are seen in prehypertensive SHR.     

Breathing pattern of spontaneously hypertensive rats

The trachea of rats anaesthetized with sodium pentobarbitone was cannulated and the air flow velocity and the pressure of the oesophagus were measured. In the spontaneously hypertensive rats the breathing frequency was higher, the tidal volume and the effective lung resistance were smaller than that of the normotensive Wistar rats. It seems that the neurohumoral control of respiration in SHR animals differs from that of normotensive rats.     

Tissue catecholamine concentrations in spontaneously hypertensive rats

Tissue concentrations of noradrenaline (NA), dopamine (DA) and adrenaline (A) were compared in spontaneously hypertensive (SHR) and normotensive (NCR) rats, aged 1, 3, 8, 14 and 24 weeks The organs analyzed included the brain, subdivided into prosencephalon and rhombencephalon, heart, adrenal glands and kidney. Brain catecholamines were significantly lower in SHR than in NCR, and the difference appeared already at the age of 3 weeks. Concomitant increase was found in the adrenal NA and A concentrations of the SHR. Concentration of NA in the heart decreased in the SHR following onset of hypertension. It is concluded that the diminished NA, DA and A concentrations in the brain as well as the augmented adrenal NA and A levels in the SHR may be causally related to the development of hypertension, while the heart NA level reflects the secondary, hypertension -- related changes.     

Angiotensin stimulates respiration in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) have an activated brain angiotensin system. We hypothesized 1) that ventilation (V) would be greater in conscious SHR than in control Wistar-Kyoto (WKY) rats and 2) that intravenous infusion of the ANG II-receptor blocker saralasin would depress respiration in SHR, but not in WKY. Respiration and oxygen consumption (VO(2)) were measured in conscious aged-matched groups (n = 16) of adult female SHR and WKY. For protocol 1, rats were habituated to a plethysmograph and measurements obtained over 60-75 min. After installation of chronic intravenous catheters, protocol 2 consisted of 30 min of saline infusion ( approximately 14 microliter. kg(-1). min(-1)) followed by 40 min of saralasin (1.3 microgram. kg(-1). min(-1)). V, tidal volume (VT), inspiratory flow [VT/inspiratory time (TI)], breath expiratory time, and VO(2) were higher, and breath TI was lower in "continuously quiet" SHR. In SHR, but not in WKY rats, ANG II-receptor block decreased V, VT, and VT/TI and increased breath TI. During ANG II-receptor block, an average decrease in VO(2) in SHR was not significant. About one-half of the higher V in SHR appears to be accounted for by an ANG II mechanism acting either via peripheral arterial receptors or circumventricular organs.     

Glutathione system in young spontaneously hypertensive rats

Glutathione (GSH) forms a part of the antioxidant system that plays a vital role in preventing oxidative stress, and an imbalance in the oxidant/antioxidant system has been linked to the pathogenesis of hypertension. The aim of this study was to investigate the status of the GSH system in the kidney of spontaneously hypertensive rats (SHR). Components of the GSH system, including glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), and total GSH content, were measured in the kidneys of 4, 6, 8, 12, and 16 weeks old SHR and Wistar–Kyoto (WKY) rats. Systolic blood pressure of SHR was significantly higher from the age of 6 weeks onwards compared with age-matched WKY rats. GPx activity in the SHR was significantly lower from the age of 8 weeks onwards when compared to that in age-matched WKY rats. No significant differences were evident in the GPx-1 protein abundance, and its relative mRNA levels, GR, GST activity, and total GSH content between SHR and age-matched WKY rats. The lower GPx activity suggests of an impairment of the GSH system in the SHR, which might be due to an abnormality in its protein rather than non-availability of a cofactor. Its role in the development of hypertension in SHR however remains unclear.     

Impaired angiotensin-induced drinking in spontaneously hypertensive rats

The drinking response during the 30 minutes following intracerebroventricular injection of angiotensin II (AII) (1 to 200 ng) was compared in male spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto control rats (WK). SHR drank significantly less than WK at the 10, 50 and 100 ng doses. In contrast, responses to intracerebroventricular carbachol and intraperitoneal hypertonic saline were not different between SHR and WK. These agents are believed to induce drinking by mechanisms independent of angiotensin. Binding of I¹²⁵-labelled AII to particles prepared from the hypothalamus, thalamus, septum and midbrain (HTSM) region was measured in one month old male and two month old female SHR and their respective age matched WK controls. No differences were found in binding between SHR and WK of either sex. These data demonstrate an impairment of drinking responses in the SHR which seem to be specific for angiotensin. This finding supports the hypothesis that the CNS angiotensin system might be abnormal in these animals.     

Body development and puberty in spontaneously hypertensive rats

The body growth and the onset of puberty in spontaneously hypertensive rats (SHR) and in normotensive controls (WKY) have been studied. In female rats the onset of puberty was determined by both the age and the body weight at which the vaginal opening and first estrus appeared, as well as the ability of estradiol and progesterone to induce pituitary LH release. For this purpose females were injected with estradiol benzoate (0.1 mg/kg) and progesterone (1 mg/rat). Control animals received only oil vehicle. In male rats, puberty was assessed by studying the age and body weight at the time of balano-preputial separation. In another experiment, SH and WKY rats were decapitated on day 30 to determine FSH, LH, PRL, GH and testosterone plasma levels in males and FSH and LH in females. The results obtained show: a) A greater body weight, at all the ages studied (every 4 days between days 28 and 92) in SHR animals. b) A delay in vaginal opening and first estrus presentation in SHR females. c) Absence of spontaneous LH peaks in WKY females. d) Advancement in balano-preputial separation in SHR males and e) Higher plasma FSH levels in SHR males than in WKY males, without differences in other hormones.     

Renal microvasculature in spontaneously hypertensive rats.

The renal microvasculature was studied in normotensive rats and in rats with spontaneous hypertension. The microvascular pattern was normal in both groups of animals, suggesting normal renin secretion. This may or may not indicate a role for renin in the cause of spontaneous hypertension.