The presence of many human pharmaceuticals in the aquatic environment is now a worldwide concern and yet little is known of the chronic effects that these bioactive substances may be having on aquatic organisms. This study used mammalian pharmacodynamics to predict the mode of action of the 13-blocker, propranolol, on fish, in order to identify chronic effects in fathead minnows. β-blockers target β1- and β2-adrenergic receptors in humans and hence these receptors were characterised in the fathead minnow. It was found that fish possess β1- and β2-ARs that are structurally very similar to their mammalian counterparts. Further, the distributions of these two β-ARs in various organs of the fathead minnow were similar to those in mammals. Pair-breeding assays were conducted, in which fathead minnows were exposed to various concentrations of propranolol. To discover whether β-ARs had been up or down regulated by propranolol, molecular analysis was conducted on different tissues of the exposed fish using real-time polymerase-chain reactions (RT-PCR). Exposure of fathead minnows to propranolol caused acute toxicity at 10 mg/L. Propranolol caused a statistically significant decrease in reproduction at 1.0 mg/L, dose-related decreases in male weight, condition index and fatpad weight, and a dose-related increase in female GSI. Molecular analysis of βl- and β2-AR expression levels revealed a dose-related decrease in β2-AR expression in fathead liver and heart. LOEC and NOEC values were 0.1 mg/L and 0.01 mg/L, respectively. Propranolol plasma concentrations in fish exposed to water concentrations of 0.1 and 1.0 mg/L were greater than the human therapeutic concentration and hence these data very strongly support the fish plasma model proposed by Huggett et al. (2001).

Class of 2012 Abstract / Specific Aims: We sought to determine the influence of genetic variation of ADRB2 on the airway response to albuterol in patients with CF when compared to matched healthy controls at baseline and at 60 minutes following the administration of albuterol (2.5mg diluted in 3ml normal saline). Methods: Baseline pulmonary function (forced vital capacity, FVC, forced expiratory flow in 1-second, FEV1, mid-maximal expiratory flow, MMF, and forced expiratory flow at 50% of the FVC) was assessed in 17 patients with CF and 31 healthy subjects. Main Results: As expected, the healthy group had higher baseline pulmonary function when compared to the CF group (FVC=97±3 vs. 83±5; FEV1=95±3 vs. 72±6; MMF=90±4 vs. 54±8, % predicted for healthy and CF, respectively, mean±SE, p<0.05 for all. We compared Arg16Arg to Arg16Gly/Gly16Gly subjects. There was no effect of genotype on the response to albuterol in healthy subjects. However, in the CF group, we found that the Arg16Arg group (n=6) had an attenuated response to β-agonist when compared to the Gly-containing group (n=11) (FVC=0±0.9 vs. 6±3: FEV1=3±1 vs. 7±4: MMF=12±3 vs. 12±5 % change, for Arg16Arg and Gly-containing groups, respectively, p<0.05 for FVC, p=0.06 for FEV1). Conclusions: These results demonstrate a differential response to β-agonists according to genetic variation of the ADRB2 at amino acid 16. Due to the differences in FVC and FEV1 but not in MMF, these data suggest that the genetic difference in airway function is primarily in bronchodilation of the larger airways.

Class of 2010 Abstract / OBJECTIVES: Cystic fibrosis (CF) is a disease that adversely affects the lung resulting in a reduction of lung diffusion. Stimulation of the β2 adrenergic receptors results in mucocilliary clearance, and therefore, lung diffusion. We sought to determine the influence of an inhaled β-­‐agonist on the diffusing capacity of the lungs for carbon monoxide (DLCO), alveolar-­‐capillary membrane conductance (DM), pulmonary capillary blood volume (Vc), and peripheral oxygen saturation (SaO2) in subjects with CF and compare the data to matched healthy subjects. METHODS: To determine this we recruited 20 healthy subjects and 18 subjects with CF (age=23±7 vs. 24±4years, ht=168±8 vs. 174±12cm. wt=64±16 vs. 70±13kg, BMI= 23±4 vs. 23±3kg/m2, FEV1= 72±27 vs. 92±12%pred., VO2peak = 45±25 vs. 99±24%pred., P<0.05 for FEV1 and VO2peak, mean±SD) for the study and measured DLCO, DM, Vc and SaO2 before and 30, 60, and 90 minutes following the administration of inhaled albuterol. RESULTS: Within the healthy subjects, there were no differences in DLCO, DM, Vc, DM/Vc at baseline or in response to albuterol according to genetic variation of the ADRB2 at amino acid 27. Within the CF group, the Glu27Glu/Gln27Glu group had higher DM/Vc when compared to the Gln27Gln group at baseline. Both genotype groups had a significant decline in Vc and a significant improvement in DM/Vc and SaO2 in response to albuterol, but not in DLCO or DM. CONCLUSIONS: These results suggest that there are differences in lung diffusion and peripheral SaO2 according to genetic variants of the ADRB2 at position 27 and could play a potential role in treatment options.

Complications in pregnancy elevate fetal norepinephrine (NE) concentrations. Previous studies in NE-infused sheep fetuses revealed that sustained exposure to high NE resulted in lower expression of α2-adrenergic receptors in islets and increased insulin secretion responsiveness after acutely terminating the NE infusion. In this study, we determined if the compensatory increase in insulin secretion after chronic elevation of NE is independent of hyperglycemia in sheep fetuses and whether it is persistent in conjunction with islet desensitization to NE. After an initial assessment of glucose-stimulated insulin secretion (GSIS) at 129 ± 1 days of gestation, fetuses were continuously infused for seven days with NE and maintained at euglycemia with a maternal insulin infusion. Fetal GSIS studies were performed again on days 8 and 12. Adrenergic sensitivity was determined in pancreatic islets collected at day 12. NE infusion increased (P < 0.01) fetal plasma NE concentrations and lowered (P < 0.01) basal insulin concentrations compared to vehicle-infused controls. GSIS was 1.8-fold greater (P < 0.05) in NE-infused fetuses compared to controls at both one and five days after discontinuing the infusion. Glucose-potentiated arginine-induced insulin secretion was also enhanced (P < 0.01) in NE-infused fetuses. Maximum GSIS in islets isolated from NE-infused fetuses was 1.6-fold greater (P < 0.05) than controls, but islet insulin content and intracellular calcium signaling were not different between treatments. The half-maximal inhibitory concentration for NE was 2.6-fold greater (P < 0.05) in NE-infused islets compared to controls. These findings show that chronic NE exposure and not hyperglycemia produce persistent adaptations in pancreatic islets that augment β-cell responsiveness in part through decreased adrenergic sensitivity.

Chicken embryos were chronically exposed to the ?1- blocker atenolol during one of three stages: mesonephros (E7-E9), mesonephros-metanephros (E11-E13), or metanephros (E15-E17). Mesonephros group hearts were larger than all other groups (P < 0.01). Mesonephros and metanephros group kidneys were larger than all remaining groups (P < 0.0001). The mesonephros group nephron number was ~40% lower than control values (P = 0.002). Glomerular areas were 26% and 18% larger than the control group in the mesonephros and metanephros groups, respectively (P < 0.001). These data suggest an E7-E9 critical window of cardiovascular and renal development for atenolol. Acute atenolol exposure in E15 embryos showed an increase in mean arterial pressure with all but the highest dose. All doses significantly decreased heart rate.

M.Sc. (Med.)--Faculty of Health Sciences, University of the Witwatersrand, 2011 / In-part through a decrease in cardiac cavity dimensions (reverse remodelling), β-adrenergic receptor blockers have been demonstrated to produce marked benefits to morbidity and mortality in patients with chronic heart failure. However, maximum doses of these agents are often difficult to achieve in patients with chronic heart failure because of the negative inotropic, hypotensive and other side effects. Whether blockade of the excessive adrenergic effects achieves complete reverse remodelling in progressive heart failure is nevertheless uncertain. To test this hypothesis I simulated the adverse effects of chronic adrenergic stimulation on the heart by administering daily doses of the β-adrenergic receptor agonist, isoproterenol (ISO) (2.42 X 10-8 mmol.kg-1) to rats for 6 months and compared left ventricular (LV) dimensions and systolic function to Saline-vehicle treated rats. To imitate the effects of complete adrenergic receptor blockade following the development of adrenergic-induced adverse cardiac changes, I similarly administered ISO for 6 months and then subsequently withdrew the daily ISO administration for a further 4 months (ISO+Recovery) before comparing left ventricular dimensions and function to Saline+Recovery treated rats. In comparison to a Saline vehicle-treated group, after 6 months of ISO administration, LV end diastolic and systolic diameters, and the volume intercept of the left ventricular diastolic pressure-volume relationship (LV V0), were markedly increased and LV endocardial fractional shortening (FSend), LV end systolic chamber (slope of the systolic pressure-volume relationship-Ees) and myocardial (slope of the systolic stress-strain relationship-En) contractility were substantially decreased. The extent of the adverse remodelling produced by chronic ISO administration was exemplified by the 2.5 times increase in LV V0 (ISO=0.40±0.04 vs Saline=0.16±0.01, p<0.001), a change proportionate to that noted in humans with chronic heart failure. iii The proportion of ISO-treated rats with LV chamber diameters, and LV V0 values above the 95% confidence interval for Saline-treated rats was markedly greater than the proportion of Saline-treated rats above their own 95% confidence intervals. Moreover, the proportion of ISO-treated rats with FSend, LV Ees and LV En values below the 95% confidence interval for Saline-treated rats was markedly greater than the proportion of Saline-treated rats below their own 95% confidence intervals. Following a 6 month period of ISO administration and a subsequent period of withdrawal of ISO administration for a further 4 months, LV chamber diameters, LV V0, FSend, LV Ees and LV En were all noted to be similar to age-matched Saline+Recovery control rats. Indeed, the increases in LV V0 observed after 6 months of ISO administration were completely reversed (ISO+Recovery=0.21±0.02 vs Saline=0.23±0.02, p<0.001). The proportion of ISO+Recovery rats with LV chamber diameters, and LV V0 values above the 95% confidence interval for the Saline+Recovery rats was similar to the proportion of Saline+Recovery rats above their own 95% confidence intervals. Moreover, the proportion of ISO+Recovery rats with FSend, LV Ees and LV En values below the 95% confidence interval for Saline+Recovery rats was similar to the proportion of Saline+Recovery rats below their own 95% confidence intervals. Chronic ISO administration and the withdrawal of ISO administration was not associated with changes in myocardial necrosis (pathological score and myocardial collagen concentrations). In conclusion, marked cardiac dilatation and pump dysfunction produced by chronic β-adrenergic receptor activation can be completely reversed by withdrawal of the excessive adrenergic stimulus. These data highlight the importance in chronic heart failure of achieving complete blockade of the pathways activated by excessive β-adrenergic receptor stimulation even in individuals with advanced cardiac dilatation.

by Lo Ping Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1987. / Includes bibliographical references.

"July 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Atrial fibrillation (AF), the most common sustained arrhythmia, is associated with abnormal intracellular Ca2+ handling. Understanding AF requires comprehensive understanding of ionic currents, Ca2+ handling, phosphorylation regulation and related signalling pathways, but appropriate models are limited. The aim of this thesis is to develop an ionic model of the mouse atrial myocyte to investigate the cellular proarrhythmic mechanisms. We have developed the first mouse atrial myocyte model that incorporates mathematically detailed ion channels, cellular Ca2+ and Na+ handling and their regulation by Ca2+-calmodulin-dependent protein kinase II (CaMKII) and protein kinase A. For the first time, the inositol 1,4,5-trisphosphate (IP3) production system and its effects on excitation-contraction coupling have also been described. The validated model predicted that: 1) hyperactivity of CaMKII and elevated intracellular Na+ concentration are the crucial factors that induce sarcoplasmic reticulum (SR) Ca2+ spontaneous release and delayed afterdepolarisations; 2) β-adrenergic stimulation may have proarrhythmic effects by exacerbating Ca2+ overload; and 3) enhanced activity in ryanodine receptors during IP3-induced Ca2+ release is the major cause of the arrhythmogenesis in IP3 signalling.

Background and objective. Cardiovascular disease (CVD) is the most important life-threatening disease. The heart is densely innervated with sympathetic fibers, however prolonged sympathetic activation can damage the heart, resulting in chronic heart failure. Recent findings suggest that norepinephrine (NE) may contribute to cardiac fibrosis and a loss of cardiomyocytes due to apoptosis. Many studies demonstrate that NE is able to induce transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF) and vascular endothelial cell growth factor (VEGF), which are two key mediators during the cardiac remodeling process. Nowadays most of the studies in cardiac remodeling are focusing on myocytes, whereas a few studies have been paid to the role of the cardiac fibroblasts (CF). In this thesis, the role of NE in cardiac fibrosis and apoptosis was investigated in CF. The mechanisms by which NE induced TGF-beta, CTGF and VEGF expression in CF were examined. Furthermore, the therapeutic potentials in cardiac fibrosis by blocking NE with adrenergic receptor antagonists were explored. / Conclusions. NE is a pathogenic molecule involving cardiac remodeling. NE exhibited its fibrotic and apoptotic effects on CF in a concentration-dependent mariner. Up-regulation of the TGF-P/CTGF pathway could be a critical mechanism of NE-induced cardiac fibrosis, while NE was capable of activating Bax-Capase 3 to cause CF apoptosis. The presence of CTGF/VEGF complex in CF in response to NE may contribute to the inhibition of angiogenesis, which may be other mechanism of ischemic heart injury. These findings indicate that an increase in NE production associated with over activation of sympathetic system is harmful to the heart and may be a major cause of chronic heart failure. Furthermore, the ability of adrenergic receptor antagonists to block NE-induced cardiac fibrosis suggest the therapeutic approach by using NE receptor antagonists for patients with chronic heart diseases. / Methods and results. Rat CF was isolated, characterized, and stimulated with NF (0.01 to 100 muM for 6 to 72h). Procollagens (I and III), TGF-beta1, bax, bclXL, CTGF and VEGF gene expressions were measured by real-time PCR method. Collagen protein level was measured by Sirius red-based colorimetric method and Western blot. CTGF protein level, VEGF concentration, cell viability, apoptosis caspase 3 activity was measured by Western blot, ELISA, MTT assay cytometry, and flurogenic assay kit, respectively. Results showed that NE at concentrations of 0.01 to 0.1 muM was capable of up-regulating procollagens, TGF-beta1 and CTGF expression (ail p&lt;0.05). However, NE at higher concentrations (10 to 100 muM) significantly induced CF apoptosis (p&lt;0.01). This was demonstrated by a significant increase in bax gene expression and caspase-3 activity, while inhibiting bclXL gene expression. At this higher concentration of NE, CTGF expression was inhibited, whereas VEGF expression was promoted. However, using immunoprecipitation, the CTGF/VEGF complex was found in CF in response to NE, thereby inhibiting angiogenesis such as tube formation in cultured endothelial cells. Interestingly, addition of NE receptor antagonists produced differential effects on procollagen expression and apoptosis. For example, carvedilol and doxazosin, the alpha-receptor-associated non-selective antagonists, were able to inhibit NE-stimulated procollagens expression, but this was not inhibited by specific beta-receptor antagonists, metoprolol and propranolol, suggesting that NE signals through the alpha-receptor to mediate cardiac fibrosis. Interestingly, all four types of adrenoceptor antagonists had no effect on NE-induced CF apoptosis, which suggests that NE induces CF apoptosis via a receptor-independent mechanism. / Lai, Ka Bik. / Adviser: Yu Cheuk Man. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3419. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 160-199). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.