No description available.

No description available.

No description available.

No description available.

During a single bout of aerobic exercise, blood flow is shunted to exercising tissues while blood flow is maintained or reduced to less metabolically active areas (i.e. splanchnic area and non-working muscles). Although increased sympathetic activation and multiple metabolic factors participate in redistributing blood flow during aerobic exercise, the precise mechanism is not entirely known. The renin-angiotensin system (RAS), specifically the local vascular wall RAS, has been hypothesized to participate in the redistribution of blood flow during exercise. This study aimed to investigate whether vascular wall RAS in the femoral arteries (an artery which feeds active tissues during exercise) was altered by acute exercise, and if these vascular RAS alterations led to specific changes in vasomotor function. Male Sprague Dawley rats were exercised on a motorized treadmill for 1h at 21m/min with 15% grade. Immediately following exercise femoral arteries were excised, cleaned of surrounding connective tissue, and vascular RAS was evaluated. There was a decrease in femoral ACE activity (~40%) and expression (~20%) following a single bout of exercise. No change was observed in AT1 and AT2 receptor expression. To evaluate the effect of acute exercise and vascular RAS on vessel reactivity, vasomotor properties of the femoral arteries were assessed via vasoconstrictor and vasodilatory dose-response curves. No changes were observed in femoral artery responses to potassium chloride (KCl), signifying that electromechanical coupling was not affected by exercise or RAS pharmacological interventions. However, a significant decrease in maximum phenylephrine (PE) constriction was observed for acutely exercise animals (~13%). Paired with the observed maintenance KCl-mediated constriction, it appears an acute bout of exercise is able to attenuate α-adrenergic receptor-mediated vasoconstriction in the femoral artery. The decrease in maximum α-adrenergic vasoconstriction may be attributed to vascular RAS. The decrease in ACE activity supports the production of local vasodilating factors. Blocking AT1 receptors with telmisartan decreased PE constriction in control and exercised animals. Combining AT1 and AT2 receptor blockade (with PD123319) eliminated the attenuating effect of telmisartan alone on PE constriction. This data suggests that the attenuating effect of AT1 receptor blockade, on PE constriction, may depend on AT2 receptor activation. In addition, combined AT1 receptor blockade and nitric oxide synthase inhibition eliminated both the lone AT1 receptor blockade effect and exercise effect on PE constriction. Together, this data suggests that reduced PE constriction following acute exercise, and AT1 receptor blockade, is dependent on nitric oxide production. Vasodilation to the nitric oxide donor sodium nitroprusside (SNP) was not altered following exercise or RAS pharmacological intervention, signifying no change in signaling downstream of NO production/release. Endothelium-dependent vasodilation to acetylcholine (ACh) was not affected by acute exercise. However, responses to ACh were modulated by RAS pharmacological interventions supporting the responses seen in PE constriction and signifying the participation of vascular RAS in vasomotor function.

During a single bout of aerobic exercise, blood flow is shunted to exercising tissues while blood flow is maintained or reduced to less metabolically active areas (i.e. splanchnic area and non-working muscles). Although increased sympathetic activation and multiple metabolic factors participate in redistributing blood flow during aerobic exercise, the precise mechanism is not entirely known. The renin-angiotensin system (RAS), specifically the local vascular wall RAS, has been hypothesized to participate in the redistribution of blood flow during exercise. This study aimed to investigate whether vascular wall RAS in the femoral arteries (an artery which feeds active tissues during exercise) was altered by acute exercise, and if these vascular RAS alterations led to specific changes in vasomotor function. Male Sprague Dawley rats were exercised on a motorized treadmill for 1h at 21m/min with 15% grade. Immediately following exercise femoral arteries were excised, cleaned of surrounding connective tissue, and vascular RAS was evaluated. There was a decrease in femoral ACE activity (~40%) and expression (~20%) following a single bout of exercise. No change was observed in AT1 and AT2 receptor expression. To evaluate the effect of acute exercise and vascular RAS on vessel reactivity, vasomotor properties of the femoral arteries were assessed via vasoconstrictor and vasodilatory dose-response curves. No changes were observed in femoral artery responses to potassium chloride (KCl), signifying that electromechanical coupling was not affected by exercise or RAS pharmacological interventions. However, a significant decrease in maximum phenylephrine (PE) constriction was observed for acutely exercise animals (~13%). Paired with the observed maintenance KCl-mediated constriction, it appears an acute bout of exercise is able to attenuate α-adrenergic receptor-mediated vasoconstriction in the femoral artery. The decrease in maximum α-adrenergic vasoconstriction may be attributed to vascular RAS. The decrease in ACE activity supports the production of local vasodilating factors. Blocking AT1 receptors with telmisartan decreased PE constriction in control and exercised animals. Combining AT1 and AT2 receptor blockade (with PD123319) eliminated the attenuating effect of telmisartan alone on PE constriction. This data suggests that the attenuating effect of AT1 receptor blockade, on PE constriction, may depend on AT2 receptor activation. In addition, combined AT1 receptor blockade and nitric oxide synthase inhibition eliminated both the lone AT1 receptor blockade effect and exercise effect on PE constriction. Together, this data suggests that reduced PE constriction following acute exercise, and AT1 receptor blockade, is dependent on nitric oxide production. Vasodilation to the nitric oxide donor sodium nitroprusside (SNP) was not altered following exercise or RAS pharmacological intervention, signifying no change in signaling downstream of NO production/release. Endothelium-dependent vasodilation to acetylcholine (ACh) was not affected by acute exercise. However, responses to ACh were modulated by RAS pharmacological interventions supporting the responses seen in PE constriction and signifying the participation of vascular RAS in vasomotor function.

The renin angiotensin aldosterone system is the dominant hormonal regulatory system controlling sodium balance and therefore blood pres- sure homeostasis. Abnormal modulation of this system is implicated in the pathogenesis of hypertension and end organ injury. We have previously developed the Cyp1a1-Ren2 transgenic rat to model an- giotensin II (ANG II) dependent hypertension. In this model hyper- tension causes renal injury, predominantly in the preglomerular vas- culature. The susceptibility to renal injury has a genetic component. A consomic/congenic study identified angiotensin converting enzyme (Ace) as an important modifer. However, renal injury is unlikely to be in uenced by a single gene. In this thesis it was hypothesised that examination of a renal microar- ray to compare the relative expression in F344 (susceptible) and Lewis (relatively protected) strains would reveal further genetic factors me- diating renal injury susceptibility. Genome wide expression analysis confirmed that Ace was a key modifier gene. Furthermore, the puriner- gic receptors P2x7 and P2x4 were identified as additional candidates. Gene and protein expression of these P2X receptors were both higher in F344 compared with Lewis. Immunohistochemistry localised P2X7 and P2X4 to the renal vasculature and tubules: the expression pattern was similar in both strains but became distinct in the renal medulla. F344, but not Lewis, responded to acute antagonism of P2X7 and P2X4. F344 showed a significant drop in blood pressure but maintained renal blood ow, indicative of tonic renal vasoconstriction. When ANG II was infused into F344 rats, there was a modest increase in blood pressure and an impairment of the pressure-natriuresis mecha- nism but no overt injury. Blood oxygenation-level dependent magnetic resonance imaging of the kidney identified a decrease in renal R2* sig- nal following P2X7 and P2X4 antagonism in ANG II infused F344 rats. P2X7/4 receptor activation reduces oxygenation and suppresses pressure-natriuresis. These effects are pro-biotic and may underpin susceptibility to renal injury.

No description available.

Ph.D., Faculty of Health Sciences, University of the Witwatersrand, 2011 / In groups of African ancestry, who have a high prevalence of “salt-sensitive, low-renin” hypertension, there is considerable uncertainty as to relevance of the renin-angiotensin-aldosterone system (RAAS) in the pathophysiology of primary hypertension. In the present thesis I explored the possibility that the RAAS, through interactions with environmental effects, contributes to blood pressure (BP) in this ethnic group. After excluding participants with aldosterone-to-renin ratios (ARR) above the threshold for primary aldosteronism, in 575 participants of African ancestry, I demonstrated that with adjustments for confounders, an interaction between ARR and urinary Na+/K+ (and index of salt intake obtained from 24-hour urine samples) was independently associated with BP (p<0.0001). This effect was accounted for by interactions between serum aldosterone concentrations and urinary Na+/K+ (p<0.0001), but not between plasma renin concentrations and urinary Na+/K+ (p=0.52). The interaction between ARR and urinary Na+/K+ translated into a marked difference in the relationship between urinary Na+/K+ and BP in participants above and below the median for ARR (p<0.0001 for a comparison of the relationships). Having demonstrated that circulating aldosterone concentrations may account for a substantial proportion of the relationship between salt intake and BP in this community sample, I subsequently assessed whether genetic factors contribute toward serum aldosterone concentrations. In 153 randomly selected nuclear families of African ancestry consisting of 448 participants without primary aldosteronism, with, but not without adjustments for plasma renin concentrations, independent correlations were noted for iii serum aldosterone concentrations between parents and children (p<0.05), with parent-child partial correlation coefficients being greater than those for father-mother relationships (p<0.05). Furthermore, after, but not before adjustments for plasma renin concentrations, serum aldosterone concentrations showed significant heritability (h2=0.25±0.12, p<0.02). No independent relationships between RAAS gene polymorphisms and serum aldosterone concentrations were observed. I also aimed to assess whether RAAS genes modify the relationship between cigarette smoking and BP in groups of African descent. However, as the impact of mild smoking on BP is uncertain, and in the community studied only 14.5% smoked and the majority of smokers were mild smokers (mean=7.4±4.6 cigarettes per day) in 689 randomly participants I initially assessed the relationship between smoking habits and out-of-office BP. In this regard, current smokers had higher unadjusted and multivariate adjusted 24-hour systolic/diastolic BP (SBP/DBP in mm Hg) (p<0.005-p<0.0005) than non-smokers, effects that were replicated in sex-specific groups, non-drinkers, and in the overweight and obese. Current smoking was second only to age and at least equivalent to body mass index in the quantitative impact on out-of-office BP and the risk of uncontrolled out-of-office BP was increased in smokers as compared to non-smokers. Thus, despite minimal effects on in-office BP, predominantly mild current smoking was independently associated with an appreciable proportion of out-of-office BP in a community of African ancestry. In 652 participants I subsequently assessed whether the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism accounts for the strong relationships between predominantly mild smoking and out-of-office BP. After iv appropriate adjustments, an interaction between ACE DD genotype and current cigarette smoking, or the number of cigarettes smoked per day was independently associated with 24-hour and day diastolic BP (DBP) (p<0.05-0.005). This effect translated into a relationship between smoking and out-of-office BP or the risk for uncontrolled out-of-office BP only in participants with the DD as compared to the ID + II genotypes. In conclusion therefore, I afford evidence to suggest that in groups of African ancestry, aldosterone, within ranges that cannot be accounted for by the presence of primary aldosteronism, modifies the relationship between salt intake and BP, and that genetic factors account for the variation in serum aldosterone concentrations in this group. Furthermore, I show that the ACE gene modifies the relationship between smoking and out-of-office BP and hence accounts for even predominantly mild smoking producing a marked and clinically important effect on out-of-office BP. The present thesis therefore provides further evidence in favour of an important pathophysiological role for the RAAS in contributing toward BP in groups of African ancestry.

Tsang, Siu Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 107-121). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Abbreviations --- p.x / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Renin-angiotensin system (RAS) --- p.1 / Chapter 1.1.1 --- Circulating RAS --- p.2 / Chapter 1.1.2 --- Tissue-specific RAS --- p.5 / Chapter 1.2 --- RAS inhibitors --- p.7 / Chapter 1.2.1 --- Angiotensin converting enzyme inhibitor --- p.8 / Chapter 1.2.2 --- Non-specific angiotensin II receptor blocker --- p.9 / Chapter 1.2.3 --- Specific AT1 receptor antagonist --- p.10 / Chapter 1.2.4 --- Specific AT2 receptor antagonist --- p.11 / Chapter 1.3 --- Pancreas and functions of exocrine pancreas --- p.14 / Chapter 1.3.1 --- Structure of pancreas --- p.14 / Chapter 1.3.2 --- Exocrine secretions and pancreatic enzymes --- p.16 / Chapter 1.3.3 --- Regulation of exocrine secretions --- p.17 / Chapter 1.4 --- Pancreatic RAS --- p.18 / Chapter 1.4.1 --- Expression and localization --- p.18 / Chapter 1.4.2 --- Regulation --- p.19 / Chapter 1.4.3 --- Clinical relevance to the pancreas --- p.20 / Chapter 1.5 --- Acute pancreatitis --- p.21 / Chapter 1.5.1 --- Pathogenesis --- p.21 / Chapter 1.5.2 --- Experimental models of acute pancreatitis --- p.22 / Chapter 1.5.3 --- Criteria of acute pancreatitis --- p.23 / Chapter 1.5.4 --- Oxidative stress in acute pancreatitis --- p.24 / Chapter 1.6 --- RAS and acute pancreatitis in exocrine pancreas --- p.26 / Chapter 1.6.1 --- RAS and acute pancreatitis --- p.26 / Chapter 1.6.2 --- RAS and pancreatic microcirculation --- p.26 / Chapter 1.6.3 --- RAS and tissue injury --- p.27 / Chapter 1.6.4 --- Exocrine pancreatic RAS and acute pancreatitis-induced injury --- p.28 / Chapter 1.7 --- Aims of study --- p.29 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Animal models and RAS inhibitors --- p.30 / Chapter 2.1.1 --- Cerulein-induced acute pancreatitis --- p.30 / Chapter 2.1.2 --- Prophylactic treatment with RAS inhibitors --- p.31 / Chapter 2.1.3 --- Therapeutic treatment with RAS inhibitors --- p.32 / Chapter 2.2 --- Evaluation of pancreatic injury --- p.32 / Chapter 2.2.1 --- Assessment of pancreatic water content --- p.33 / Chapter 2.2.2 --- Measurement of α-amylase activity in plasma --- p.33 / Chapter 2.2.3 --- Measurement of lipase activity in plasma --- p.34 / Chapter 2.3 --- Histopathological examinations --- p.34 / Chapter 2.3.1 --- Preparation of paraffin blocks --- p.35 / Chapter 2.3.2 --- Hematoxylin and eosin staining --- p.35 / Chapter 2.4 --- Biochemical assay of pancreatic oxidative status --- p.37 / Chapter 2.4.1 --- Sample preparation --- p.37 / Chapter 2.4.2 --- Quantification of protein content --- p.37 / Chapter 2.4.3 --- Measurement of glutathione levels --- p.38 / Chapter 2.4.4 --- Assessment of protein oxidation --- p.38 / Chapter 2.4.5 --- Assessment of lipid peroxidation --- p.39 / Chapter 2.4.6 --- Measurement of NADPH oxidase activity --- p.40 / Chapter 2.5 --- Studies of pancreatic digestive enzyme secretions from isolated acini --- p.40 / Chapter 2.5.1 --- Dissociation of acini from pancreatic tissue --- p.40 / Chapter 2.5.2 --- Treatment with peptides and RAS inhibitors --- p.42 / Chapter 2.5.3 --- Quantification of protein and DNA contents --- p.43 / Chapter 2.5.4 --- Measurement of a-amylase and lipase secretions --- p.44 / Chapter 2.5.5 --- RT-PCR analysis of RAS components in acinar cells --- p.44 / Chapter 2.6 --- Studies of RAS inhibitors on acute pancreatitis-induced systemic inflammation --- p.45 / Chapter 2.6.1 --- Systemic inflammation treatment --- p.45 / Chapter 2.6.2 --- Measurement of myeloperoxidase activity in lung and liver --- p.46 / Chapter 2.7 --- Statistical analysis --- p.47 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Time-course experiment of acute pancreatitis model --- p.48 / Chapter 3.1.1 --- Effect of acute pancreatitis on tissue injury --- p.48 / Chapter 3.1.2 --- Effects of acute pancreatitis on oxidative status --- p.48 / Chapter 3.2 --- Evaluation of ramiprilat and saralasin on changes of acute pancreatitis- induced pancreatic injury --- p.50 / Chapter 3.2.1 --- Changes in tissue injury and histopathology --- p.50 / Chapter 3.2.2 --- Changes in oxidative status --- p.57 / Chapter 3.3 --- Evaluation of losartan and PD123319 on changes of acute pancreatitis- induced pancreatic injury --- p.61 / Chapter 3.3.1 --- Changes in tissue injury and histopathology --- p.61 / Chapter 3.3.2 --- Changes in oxidative status --- p.68 / Chapter 3.4 --- Evaluation of acinar secretions of digestive enzymes --- p.71 / Chapter 3.4.1 --- Cholecystokinin octapeptide-induced acinar secretions --- p.71 / Chapter 3.4.2 --- Angiotensin II-induced acinar secretions --- p.71 / Chapter 3.4.3 --- Effects of losartan and PD 123319 on α-amylase secretion --- p.74 / Chapter 3.5 --- Existence and regulation of acinar RAS by acute pancreatitis --- p.75 / Chapter 3.5.1 --- Expression of angiotensinogen and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.2 --- Expression of AT1 receptor and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.3 --- Expression of AT2 receptor and its regulation by acute pancreatitis in acini --- p.76 / Chapter 3.5.4 --- Evaluation of RAS inhibitors in acute pancreatitis-induced acinar cells --- p.80 / Chapter 3.6 --- Preliminary data on acute pancreatitis-induced systemic inflammation --- p.81 / Chapter 3.6.1 --- Time-course experiment on lung injury --- p.81 / Chapter 3.6.2 --- Time-course experiment on liver injury --- p.83 / Chapter 3.6.3 --- Evaluation of losartan on systemic inflammation --- p.85 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- "Actions of RAS inhibitors on the changes of tissue injury, oxidative status and histopathology in acute pancreatitis-induced pancreas" --- p.87 / Chapter 4.1.1 --- Differential effects of ramiprilat and saralasin --- p.88 / Chapter 4.1.2 --- Differential effects of losartan and PD123319 --- p.92 / Chapter 4.2 --- Potential functions of RAS in pancreatic acinar secretions --- p.95 / Chapter 4.2.1 --- Potential role of AT1 receptor --- p.96 / Chapter 4.2.2 --- Potential role of AT2 receptor --- p.98 / Chapter 4.3 --- Regulation of RAS in acute pancreatitis-induced acini --- p.98 / Chapter 4.3.1 --- Regulation of RAS components in acinar cells --- p.99 / Chapter 4.3.2 --- Differential actions of losartan and PD123319 --- p.100 / Chapter 4.4 --- Potential role of RAS in acute pancreatitis --- p.102 / Chapter 4.4.1 --- Regulation of RAS components by acute pancreatitis --- p.102 / Chapter 4.4.2 --- Differential functions of AT1 and AT2 receptors in acute pancreatitis --- p.103 / Chapter 4.5 --- Conclusion --- p.104 / Chapter 4.6 --- Further studies --- p.105 / Chapter Chapter 5 --- Bibliography --- p.107