Effects of intrarenal pelvic infusion of tumour necrosis factor-α and interleukin 1-β on reno-renal reflexes in anaesthetised rats

OBJECTIVE

Reno-renal reflexes are disturbed in cardiovascular and hypertensive conditions when elevated levels of pro-inflammatory mediators/cytokines are present within the kidney. We hypothesised that exogenously administered inflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin (IL)-1β modulate the renal sympatho-excitatory response to chemical stimulation of renal pelvic sensory nerves.

METHODS

In anaesthetised rats, intrarenal pelvic infusions of vehicle [0.9% sodium chloride (NaCl)], TNF-α (500 and 1000 ng/kg) and IL-1β (1000 ng/kg) were maintained for 30 min before chemical activation of renal pelvic sensory receptors was performed using randomized intrarenal pelvic infusions of hypertonic NaCl, potassium chloride (KCl), bradykinin, adenosine and capsaicin.

RESULTS

The increase in renal sympathetic nerve activity (RSNA) in response to intrarenal pelvic hypertonic NaCl was enhanced during intrapelvic TNF-α (1000 ng/kg) and IL-1β infusions by almost 800% above vehicle with minimal changes in mean arterial pressure (MAP) and heart rate (HR). Similarly, the RSNA response to intrarenal pelvic adenosine in the presence of TNF-α (500 ng/kg), but not IL-1β, was almost 200% above vehicle but neither MAP nor HR were changed. There was a blunted sympatho-excitatory response to intrapelvic bradykinin in the presence of TNF-α (1000 ng/kg), but not IL-1β, by almost 80% below vehicle, again without effect on either MAP or HR.

CONCLUSION

The renal sympatho-excitatory response to renal pelvic chemoreceptor stimulation is modulated by exogenous TNF-α and IL-1β. This suggests that inflammatory mediators within the kidney can play a significant role in modulating the renal afferent nerve-mediated sympatho-excitatory response.

Effects of renal denervation on kidney function in patients with chronic kidney disease: a systematic review and meta-analysis

The present study aims to evaluate the clinical outcomes following renal denervation (RDN) for hypertensive patients with chronic kidney disease (CKD). Prospective studies published between January 1, 2010 and November 15, 2022 where systematically identified for RDN outcomes on office and ambulatory blood pressure, estimated glomerular filtration rate (eGFR), creatinine and procedural characteristics from three online databases (Medline, PubMed, EMBASE). Random effects model to combine risk ratios and mean differences was used. Where possible, clinical outcomes were pooled and analyzed at 6, 12 and 24 months. Significance was set at p ≤ 0.05. 11 prospective trials, with a total of 226 patients with treatment resistant HTN receiving RDN met the inclusion criteria. Age ranged from 42.5 ± 13.8 to 66 ± 9. Main findings of this review included a reduction in systolic and diastolic office blood pressure at 6 [-19.8 (p < 0.00001)/-15.2 mm Hg (p < 0.00001)] and 12 months [-21.2 (p < 0.00001)/-9.86 mm Hg (p < 0.0005)] follow-up compared to baseline. This was also seen in systolic and diastolic 24-hour ambulatory blood pressure at 6 [-9.77 (p = 0.05)/-3.64 mm Hg (p = 0.09)] and 12 months [-13.42 (p = 0.0007)/-6.30 mm Hg (p = 0.001)] follow-up compared to baseline. The reduction in systolic and diastolic 24-hour ambulatory blood pressure was maintained to 24 months [(-16.30 (p = 0.0002)/-6.84 mm Hg (p = 0.0010)]. Analysis of kidney function through eGFR demonstrated non-significant results at 6 (+1.60 mL/min/1.73 m2, p = 0.55), 12 (+5.27 mL/min/1.73 m2, p = 0.17), and 24 months (+7.19 mL/min/1.73 m2, p = 0.36) suggesting an interruption in natural CKD progression. Similar results were seen in analysis of serum creatinine at 6 (+0.120 mg/dL, p = 0.41), 12 (+0.100 mg/dL, p = 0.70), and 24 months (+0.07 mg/dL, p = 0.88). Assessment of procedural complications deemed RDN in a CKD cohort to be safe with an overall complication rate of 4.86%. With the current advances in RDN and its utility in multiple chronic diseases beyond hypertension, the current study summarizes critical findings that further substantiate the literature regarding the potential of such an intervention to be incorporated as an effective treatment for resistant hypertension and CKD.

Green synthesized silver nanoparticles using the plant-based reducing agent Matricaria chamomilla induce cell death in colorectal cancer cells

OBJECTIVE

There is a need to treat cancer cells with safe and natural nanoparticles to avoid the side effects of chemotherapeutic agents. Chamomile is considered a safe, natural plant with anticancer activity. We synthesize simple, inexpensive, and eco-friendly silver nanoparticles (SNs) using Chamomile (CHM) to tune their anticancer properties.

MATERIALS AND METHODS

SN-CHM was synthesized by reducing 1 mM silver nitrate aqueous solution in 100 mL with the aqueous ethanolic flower extract of CHM (18 mg/mL, w/v). The reaction proceeded overnight at 600 rpm and 28°C. SN-CHM was characterized for their % yield, average diameter, charge, morphology, and silver release. Moreover, SN-CHM was investigated for its antioxidant and anticancer activities at 200 µg/mL and 5 mg/ mL, respectively.

RESULTS

A 59.12% yield and a uniform SN-CHM size of 115 ± 3.1 nm with a ζ-potential of -27.67 ± (-3.92) mv were observed. The UV-visible absorption showed shifts from 379.5 to 383.5 nm for CHM and SN-CHM, respectively. Moreover, Ag+ was ultimately released from SN-CHM after 5 h. Fourier Transform Infrared Spectroscopy (FT-IR) showed characteristic absorption peaks of CHM and produced SN-CHM. Furthermore, SN-CHM showed moderate antioxidant activity. SN-CHM inhibited the % viability of SW620 and HT-29 cell lines at 20 μM. SN-CHM may also greatly upregulate the apoptotic gene BAX while considerably downregulating the anti-apoptotic genes BCL2 and BCL-Xl.

CONCLUSIONS

CHM can be a safe soft drink, especially when conjugated with Ag ions as anticancer NPs. SN-CHM is considered potent anticancer activity against SW620, and HT-29 cell lines.

An investigation of pre-clinical medical students' preference for summative or formative assessment for physiology learning

Both summative and formative assessments are known to facilitate student learning and understanding and helps them to identify areas of weakness. However, few studies have investigated students' preference for either summative or formative evaluations, particularly in the area of pre-clinical medicine. The current study addresses this deficit by surveying 137 first year graduate entry to medicine (GEM) pre-clinical medical students from two consecutive years (2018-19 & 2019-20), for their thoughts on the five summative (i.e. for a small percentage of marks), proctored, and the four informal, formative (i.e. no marks available) continuous assessments in physiology that they encountered in semesters 1 and 2, respectively. Our survey revealed that between 75-90% of students felt that both evaluation formats were roughly equally useful (i.e. selecting options, 'Agree' or 'Strongly Agree') both for providing feedback about their understanding of physiology, and for identifying deficits in their physiology knowledge. However, although a significantly larger number of students felt that summative evaluations motivated them to study more than the formative evaluations (p=0.006), overall, more students favored formative over summative assessments. Notably however, GEM students from non-biomedical backgrounds were significantly more in favor of summative assessments than those from either biomedical backgrounds (p=0.003) or the whole GEM survey cohort (p=0.01). The implications of these findings will be discussed, with suggestions as to how the student views outlined here might be facilitated within an academic program to maximise both student learning as well as their motivation to study and keep up with taught material.

A comprehensive review on the pancreatic lipase inhibitory peptides: A future anti-obesity strategy

Dysregulation of lipid homeostasis contributes to obesity and can directly lead to several critical public health concerns globally. This paper aimed to present a brief review of related properties and the use of pancreatic lipase inhibitors as the future weight loss drug discovery and development procured from a wide range of natural sources. A total of 176 pancreatic lipase inhibitory peptides were identified from recent publications and peptide databases. These peptides were classified into three categories according to their peptide length and further analyzed using bioinformatic approaches to identify their structural activity relationship. Molecular docking analyses were conducted for each amino acid at the terminal position of the peptides to predict the binding affinity between peptide-enzyme protein complexes based on intermolecular contact interactions. Overall, the observations revealed the features of the inhibitory peptides and their inhibitory mechanisms and interactions. These findings strived to benefit scientists whose research may be relevant to anti-obesity drug development and/or discovery thereby support effective translation of preclinical research for humans’ health being.

Effects of intrarenal angiotensin 1-7 infusion on renal haemodynamic and excretory function in anaesthetised two-kidney one-clip and deoxycorticosterone acetate-salt hypertensive rats

NEW FINDINGS

What is the central question of this study? Are renal functional responses to intrarenal angiotensin 1-7 (Ang (1-7)) infusion dependent on the level of the endogenous renin-angiotensin system (RAS) in the two-kidney one-clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt animal models of hypertension? What is the main finding and its importance? The renal actions of Ang (1-7) are dependent on the relative endogenous levels of each arm of the classical angiotensin II-angiotensin II type 1 receptor (AT1 R) axis and those of the Ang (1-7)-Mas receptor axis. These findings support the hypothesis that a balance exists between the intrarenal classical and novel arms of the RAS, and in particular the relative abundance of AT1 R to Mas receptor, which may to a large extent determine the renal excretory response to Ang (1-7) infusion.

ABSTRACT

This study investigated the action of angiotensin 1-7 (Ang (1-7)) on renal haemodynamic and excretory function in the two-kidney one-clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt rat models of hypertension, in which the endogenous renin-angiotensin system (RAS) activity was likely to be raised or lowered, respectively. Rats were anaesthetised and prepared for the measurement of mean arterial pressure and kidney function during renal interstitial infusion of Ang (1-7) or saline. Kidney tissue concentrations of angiotensin II (Ang II) and Ang (1-7) were determined. Intrarenal infusion of Ang (1-7) into the clipped kidney of 2K1C rats increased urine flow (UV), absolute (UNa V) and fractional sodium (FENa ) excretions by 110%, 214% and 147%, respectively. Renal Ang II concentrations of the clipped kidney were increased with no major changes in Ang (1-7) concentration. By contrast, Ang (1-7) infusion decreased UV, UNa V, and FENa by 27%, 24% and 21%, respectively in the non-clipped kidney in which tissue Ang (1-7) concentrations were increased, but renal Ang II concentrations were unchanged compared to sham animals. Ang (1-7) infusion in DOCA-salt rats had minimal effects on glomerular filtration rate but significantly decreased UV, UNa V and FENa by ∼30%. Renal Ang (1-7) concentrations were higher and Ang II concentrations were lower in DOCA-salt rats compared to sham rats. These findings demonstrate that the intrarenal infusion of exogenous Ang (1-7) elicits different renal excretory responses the magnitude of which is dependent on the balance between the endogenous renal Ang II-AT1 receptor axis and Ang (1-7)-Mas receptor axis.

Intrarenal pelvic bradykinin-induced sympathoexcitatory reno-renal reflex is attenuated in rats exposed to chronic intermittent hypoxia

OBJECTIVE

In this study, we hypothesized that excitatory reno-renal reflex control of sympathetic outflow is enhanced in rats exposed to chronic intermittent hypoxia (CIH) with established hypertension.

METHODS

Under anaesthesia, renal sensory nerve endings in the renal pelvic wall were chemically activated using bradykinin (150, 400 and 700 μmol/l) and capsaicin (1.3 μmol/l), and cardiovascular parameters and renal sympathetic nerve activity (RSNA) were measured.

RESULTS

CIH-exposed rats were hypertensive with elevated basal heart rate and increased basal urine flow compared with sham. The intrarenal pelvic infusion of bradykinin was associated with contralateral increase in the RSNA and heart rate, without concomitant changes in blood pressure. This was associated with a drop in the glomerular filtration rate, which was significant during a 5 min period after termination of the infusion but without significant changes in urine flow and absolute sodium excretion. In response to intrarenal pelvic infusion of 700 μmol/l bradykinin, the increases in RSNA and heart rate were blunted in CIH-exposed rats compared with sham rats. Conversely, the intrarenal pelvic infusion of capsaicin evoked an equivalent sympathoexcitatory effect in CIH-exposed and sham rats. The blockade of bradykinin type 1 receptors (BK1R) suppressed the bradykinin-induced increase in RSNA by ∼33%, with a greater suppression obtained when bradykinin type 2 receptors (BK2R) and BK1R were contemporaneously blocked (∼66%).

CONCLUSION

Our findings reveal that the bradykinin-dependent excitatory reno-renal reflex does not contribute to CIH-induced sympathetic hyperactivity and hypertension. Rather, there is evidence that the excitatory reno-renal reflex is suppressed in CIH-exposed rats, which might relate to a downregulation of BK2R.

A Narrative Review on the Phytochemistry, Pharmacology and Therapeutic Potentials of Clinacanthus nutans (Burm. f.) Lindau Leaves as an Alternative Source of Future Medicine

The application of natural products and supplements has expanded tremendously over the past few decades. Clinacanthus nutans (C. nutans), which is affiliated to the Acanthaceae family, has recently caught the interest of researchers from the countries of subtropical Asia due to its medicinal uses in alternative treatment for skin infection conditions due to insect bites, microorganism infections and cancer, as well as for health well-being. A number of bioactive compounds from this plant's extract, namely phenolic compounds, sulphur containing compounds, sulphur containing glycosides compounds, terpens-tripenoids, terpens-phytosterols and chlorophyll-related compounds possess high antioxidant activities. This literature search yielded about one hundred articles which were then further documented, including the valuable data and findings obtained from all accessible electronic searches and library databases. The promising pharmacological activities from C. nutans leaves extract, including antioxidant, anti-cancer, anti-viral, anti-bacterial, anti-fungal, anti-venom, analgesic and anti-nociceptive properties were meticulously dissected. Moreover, the authors also discuss a few of the pharmacological aspect of C. nutans leaves extracts against anti-hyperlipidemia, vasorelaxation and renoprotective activities, which are seldom available from the previously discussed review papers. From the aspect of toxicological studies, controversial findings have been reported in both in-vitro and in-vivo experiments. Thus, further investigations on their phytochemical compounds and their mode of action showing pharmacological activities are required to fully grasp both traditional usage and their suitability for future drugs development. Data related to therapeutic activity and the constituents of C. nutans leaves were searched by using the search engines Google scholar, PubMed, Scopus and Science Direct, and accepting literature reported between 2010 to present. On the whole, this review paper compiles all the available contemporary data from this subtropical herb on its phytochemistry and pharmacological activities with a view towards garnering further interest in exploring its use in cardiovascular and renal diseases.

The renal excretory responses to acute renal interstitial angiotensin (1-7) infusion in anaesthetised spontaneously hypertensive rats

This study investigated the impact of intrarenal angiotensin 1-7 (Ang [1-7]) infusion on renal excretory function in a rat model of hypertension. Eleven-week-old spontaneously hypertensive rats (SHRs, n = 7) and Han Wistar controls (NCR, n = 7) were anaesthetised with sodium pentobarbital (60 mg/kg i.p.) and prepared for the measurement of mean arterial pressure (MAP) and left renal function during renal interstitial infusion of Ang (1-7) (50 ng/min). The kidneys were harvested, the renal cortex and medulla separated, prepared for measurement of Ang II and Ang (1-7) and Western blot determination of AT1 and Mas receptor protein expression. MAP, glomerular filtration rate (GFR), urine flow (UF) and absolute sodium excretion (UNaV) were 109 ± 16 mmHg, 4.4 ± 1.0 mL/min/kg, 102 ± 16 µL/min/kg and 16 ± 3 µmol/min/kg, respectively in the NCR and 172 ± 24 mmHg, 3.4 ± 0.7 mL/min/kg, 58 ± 30 μL/min/kg and 8.6 ± 4.8 μmol/min/kg respectively in the SHR. Ang (1-7) increased UF (31%), U_Na V (50%) and fractional sodium excretion (FENa⁺ ) (22%) in the NCR group (all p < 0.05) but had no effect on GFR in either group. The magnitudes of the Ang (1-7)-induced increases in UF and U_Na V were significantly blunted in the SHR group (model × drug p < 0.05). The renal cortical AT1: Mas receptor expression ratio was significantly higher in the SHR group (p < 0.05) but renal Ang II and Ang (1-7) levels were not statistically different between groups. The Ang (1-7)-induced increases in sodium and water excretion were impaired in the SHR group in the context of an unstimulated RAS. The decrease in responsiveness of the SHR kidney to Ang (1-7) appears to be associated with higher levels of AT1 receptor expression in the renal cortex.

Exposure to High-Fat Style Diet Induced Renal and Liver Structural Changes, Lipid Accumulation and Inflammation in Intact and Ovariectomized Female Rats

Purpose

We hypothesized that low estrogen levels aggravate obesity-related complications. Diet-induced obesity can cause distinct pathologies, including impaired glucose tolerance, inflammation, and organ injury that leads to fatty liver and chronic kidney diseases. To test this hypothesis, ovariectomized (OVX) rats were fed a high-fat style diet (HFSD), and we examined structural changes and inflammatory response in the kidney and liver.

Methods

Sprague-Dawley female rats were ovariectomized or sham-operated and divided into four groups: sham-operated rats fed a normal diet (ND); ovariectomized rats fed a normal diet (OVX-ND); sham-operated rats fed a HFSD; ovariectomized rats fed a high-fat style diet (OVX-HFSD). Mean blood pressure and fasting blood glucose were measured on weeks 0 and 10. The rats were sacrificed 10 weeks after initiation of ND or HFSD, the kidney and liver were harvested for histological, immunohistochemical and immunofluorescence studies.

Results

HFSD-fed rats presented a significantly greater adiposity index compared to their ND counterparts. Liver index, fasting blood glucose and mean blood pressure was increased in OVX-HFSD rats compared to HFSD rats at study terminal. Histological and morphometric studies showed focal interstitial mononuclear cell infiltration in the kidney of HFSD rats with mesangial expansion being greater in the OVX-HFSD rats. Both HFSD fed groups showed increased expressions of renal inflammatory markers, namely TNF-alpha, IL-6 and MCP-1, and infiltrating M1 macrophages with some influence of ovarian hormonal status. HFSD-feeding also caused hepatocellular steatosis which was aggravated in ovariectomized rats fed the same diet. Furthermore, hepatocellular ballooning was observed only in the OVX-HFSD rats. Similarly, HFSD-fed rats showed increased expressions of the inflammatory markers and M1 macrophage infiltration in the liver; however, only IL-6 expression was magnified in the OVX-HFSD.

Conclusion

Our data suggest that some of the structural changes and inflammatory response in the kidney and liver of rats fed a HFSD are exacerbated by ovariectomy.

Inhibition of L-NAME-induced hypertension by combined treatment with apocynin and catalase: the role of Nox 4 expression

Reactive oxygen species (ROS) such as superoxide (O2-) generated by NAD(P)H oxidases have emerged as important molecules in blood pressure regulation. This study investigated the effect of apocynin and catalase on blood pressure and renal haemodynamic and excretory function in an L-NAME induced hypertension model. Forty Male Wistar-Kyoto (WKY) rats (n=8 per group) were treated with either: vehicle (WKY-C); L-NAME (WKY-L, 15 mg/kg/day in drinking fluid); WKY-L given apocynin to block NAD(P)H oxidase (WKY-LApo, 73 mg/kg/day in drinking water.); WKY-L given catalase to enhance ROS scavenging (WKY-LCat, 10000 U/kg/day i.p.); and WKY-L receiving apocynin plus catalase (WKY-LApoCat) daily for 14 days. L-NAME elevated systolic blood pressure (SBP), 116+/-1 to 181±4 mmHg, reduced creatinine clearance, 1.69+/-0.26 to 0.97+/-0.05 ml/min/kg and fractional sodium excretion, 0.84+/-0.09 to 0.55+/-0.09 % at day 14. Concomitantly, plasma malondialdehyde (MDA) increased six fold, while plasma total superoxide dismutase (T-SOD), plasma nitric oxide (NO) and plasma total antioxidant capacity (T-AOC) were decreased by 60-70 % and Nox 4 mRNA expression was increased 2-fold. Treatment with apocynin and catalase attenuated the increase in SBP and improved renal function, enhanced antioxidative stress capacity and reduced the magnitude of Nox4 mRNAs expression in the L-NAME treated rats. This study demonstrated that apocynin and catalase offset the development of L-NAME induced hypertension, renal dysfunction and reduced oxidative stress status, possibly contributed by a reduction in Nox4 expression during NOS inhibition. These findings would suggest that antioxidant compounds such as apocynin and catalase have potential in treating cardiovascular diseases.

Chronic intermittent hypoxia impairs diuretic and natriuretic responses to volume expansion in rats with preserved low-pressure baroreflex control of the kidney

We examined the effects of exposure to chronic intermittent hypoxia (CIH) on baroreflex control of renal sympathetic nerve activity (RSNA) and renal excretory responses to volume expansion (VE) before and after intrarenal transient receptor potential vanilloid 1 (TRPV1) blockade by capsaizepine (CPZ). Male Wistar rats were exposed to 96 cycles of hypoxia per day for 14 days (CIH) or normoxia. Urine flow and absolute Na+ excretion during VE were less in CIH-exposed rats, but the progressive decrease in RSNA during VE was preserved. Assessment of the high-pressure baroreflex revealed an increase in the operating and response range of RSNA and decreased slope in CIH-exposed rats with substantial hypertension [+19 mmHg basal mean arterial pressure (MAP)] but not in a second cohort with modest hypertension (+12 mmHg). Intrarenal CPZ caused diuresis, natriuresis, and a reduction in MAP in sham-exposed (sham) and CIH-exposed rats. After intrarenal CPZ, diuretic and natriuretic responses to VE in CIH-exposed rats were equivalent to those of sham rats. TRPV1 expression in the renal pelvic wall was similar in both experimental groups. Exposure to CIH did not elicit glomerular hypertrophy, renal inflammation, or oxidative stress. We conclude that exposure to CIH 1) does not impair the low-pressure baroreflex control of RSNA; 2) has modest effects on the high-pressure baroreflex control of RSNA, most likely indirectly due to hypertension; 3) can elicit hypertension in the absence of kidney injury; and 4) impairs diuretic and natriuretic responses to fluid overload. Our results suggest that exposure to CIH causes renal dysfunction, which may be relevant to obstructive sleep apnea.

Effects of intracerebroventricular leptin and orexin-A on the baroreflex control of renal sympathetic nerve activity in conscious rats fed a normal or high-fat diet

This study examined the effect of leptin and orexin-A on autonomic baroreflex control in conscious Wistar rats exposed to high-fat (45% fat) or normal (3.4%) diet for 4 weeks. Renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were monitored during the generation of baroreflex gain curves and acute volume expansion (VEP). Intracerebroventricular (ICV) leptin (1 μg/min) increased RSNA in the normal diet group (0.31 ± 0.04 vs 0.23 ± 0.03 mV/s) and MAP in the high-fat diet group (115 ± 5 vs 105 ± 5 mm Hg, P < .05). Orexin-A (50 ng/min) increased RSNA, HR and MAP in the high-fat diet group (0.26 ± 0.03 vs 0.22 ± 0.02 mV/s, 454 ± 8 vs 417 ± 12 beats/min, 117 ± 1 vs 108 ± 1 mm Hg) and the normal diet group (0.18 ± 0.05 vs 0.17 ± 0.05 mV/s, 465 ± 10 vs 426 ± 6 beats/min, 116 ± 2 vs 104 ± 3 mm Hg). Baroreflex sensitivity for RSNA was increased during ICV leptin by 50% in the normal diet group, compared to 14% in the high-fat diet group (P < .05). Similarly, orexin-A increased baroreflex sensitivity by 56% and 50% in the high-fat and normal diet groups, respectively (all P < .05). During ICV saline, VEP decreased RSNA by 31 ± 5% (P < .05) after 10 minutes and the magnitude of this response was blunted during ICV infusion of leptin (17 ± 2%, P < .05) but not orexin-A in the normal diet group. RSNA response to VEP was not changed during ICV leptin or orexin-A in the high-fat diet group. These findings indicate possible central roles for leptin and orexin-A in modulating the baroreflexes under normal or increased fat intake in conscious rats and potential therapeutic approaches for obesity associated hypertension.

The restorative effect of apocynin and catalase in l-arginine induced hypotension on normotensive subjects - the role of oxidative stress

L-arginine is a substrate for nitric oxide synthase (NOS) responsible for the production of NO. This investigation studied the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on L-arginine induced oxidative stress and hypotension. Forty Wistar-Kyoto rats were treated for 14 days with vehicle, L-arginine (12.5mg/ml p.o.), L-arginine+apocynin (2.5mmol/L p.o.), L-arginine+catalase (10000U/kg/day i.p.) and L-arginine plus apocynin+catalase respectively. Weekly renal functional and hemodynamic parameters were measured and kidneys harvested at the end of the study for histopathological and renal NADPH oxidase 4 (Nox4) assessments. L-arginine administration in normotensive rats decreased systolic blood pressure (120±2 vs 91±2mmHg) and heart rate (298±21 vs 254±15b/min), enhanced urinary output (21.5±4.2 vs 32±1.9ml/24h , increased creatinine clearance (1.72±0.56 vs 2.62±0.40ml/min/kg), and fractional sodium excretion (0.88±0.16 vs 1.18±0.16 %), caused proteinuria (28.10±1.93 vs 35.26±1.69mg/kg/day) and a significant decrease in renal cortical blood perfusion (292±3 vs 258±5bpu) and pulse wave velocity (3.72±0.20 vs 2.84±0.13m/s) (all P<0.05). L-arginine increased plasma malondialdehyde (by ~206 % P<0.05) and NO (by~51 %, P<0.05) but decreased superoxide dismutase (by~31 %, P<0.05) and total antioxidant capacity (by~35 %, P<0.05) compared to control. Renal Nox4 mRNA activity was approximately 2.1 fold higher (P<0.05) in the L-arginine treated rats but was normalized by apocynin and apocynin plus catalase treatment. Administration of apocynin and catalase, but not catalase alone to rats fed L-arginine, restored the deranged renal function and structure, prevented hypotension and enhanced the antioxidant capacity and suppressed Nox4 expression. These findings suggest that apocynin and catalase might be used prophylactically in states of oxidative stress.

The Impact of Supplementing PowerPoint with Detailed Notes and Explanatory Videos on Student Attendance and Performance in a Physiology Module in Medicine

PowerPoint is widely used in higher education with reported advantages on student learning. The aim of this study was to examine the impact of detailed notes and videos as a supplement to PowerPoint slides on student attendance and performance. First-year medical students' opinion on whether the supplementary material assisted their learning of Physiology in addition to demographics was collected in a survey. Attendance was similar for participants who used notes and videos to those who did not, for male vs. female and for participants from biomedical vs. non-biomedical backgrounds. However, within the non-biomedical cohort, attendance of male respondents was significantly higher (95 ± 3 vs. 81 ± 6%, P < 0.05), although both groups used notes and videos. Similarly, attendance of female participants of biomedical background was higher (P < 0.05) than female participants of non-biomedical background (biomedical vs. non-biomedical: 94 ± 3 vs. 81 ± 6%) even though both cohorts used notes and videos. Providing notes and videos had no adverse impact on attendance (90 ± 2%, 8 lectures) and tended to enhance exam scores for low-performing students in the class when compared with those of previous years' cohorts (2018 vs. 2017 and 2016: 61 ± 5% vs. 55 ± 6% and 47 ± 8%, respectively). There was an increase in the immediate gain of knowledge following watching/listening to videos (after vs. before: 65 ± 3% vs. 48 ± 3%). The survey revealed a positive student perception of supplementary material mainly because they felt it reduced the time required to search for relevant information.

Is Aberrant Reno-Renal Reflex Control of Blood Pressure a Contributor to Chronic Intermittent Hypoxia-Induced Hypertension?

Renal sensory nerves are important in the regulation of body fluid and electrolyte homeostasis, and blood pressure. Activation of renal mechanoreceptor afferents triggers a negative feedback reno-renal reflex that leads to the inhibition of sympathetic nervous outflow. Conversely, activation of renal chemoreceptor afferents elicits reflex sympathoexcitation. Dysregulation of reno-renal reflexes by suppression of the inhibitory reflex and/or activation of the excitatory reflex impairs blood pressure control, predisposing to hypertension. Obstructive sleep apnoea syndrome (OSAS) is causally related to hypertension. Renal denervation in patients with OSAS or in experimental models of chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoeas (pauses in breathing), results in a decrease in circulating norepinephrine levels and attenuation of hypertension. The mechanism of the beneficial effect of renal denervation on blood pressure control in models of CIH and OSAS is not fully understood, since renal denervation interrupts renal afferent signaling to the brain and sympathetic efferent signals to the kidneys. Herein, we consider the currently proposed mechanisms involved in the development of hypertension in CIH disease models with a focus on oxidative and inflammatory mediators in the kidneys and their potential influence on renal afferent control of blood pressure, with wider consideration of the evidence available from a variety of hypertension models. We draw focus to the potential contribution of aberrant renal afferent signaling in the development, maintenance and progression of high blood pressure, which may have relevance to CIH-induced hypertension.

Effect of pioglitazone on vasopressor responses to adrenergic agonists and angiotensin II in diabetic and non-diabetic spontaneously hypertensive rats

Pioglitazone, peroxisome proliferator-activated receptor (PPAR-γ) agonist, is a therapeutic drug for diabetes. Present study investigated the interaction between PPAR-γ and alpha adrenoceptors in modulating vasopressor responses to Angiotensin II (Ang II) and adrenergic agonists, in diabetic & non-diabetic Spontaneously Hypertensive Rats (SHRs). Diabetes was induced with an i.p injection of streptozotocin (40 mg/kg) in two groups (STZ-CON, STZ-PIO), whereas two groups remained non diabetic (ND-CO, ND-PIO). One diabetic and non-diabetic group received Pioglitazone (10mg/kg) orally for 21 days. On day 28, the animals were anaesthetized with sodium pentobarbitone (60mg/kg) and prepared for measurement of systemic haemodynamics. Basal mean arterial pressure of STZ-CON was higher than ND-CON, whereas following pioglitazone treatment, MAP was lower compared to respective controls. MAP responses to i.v administration of NA, PE, ME and ANG II were significantly lower in diabetic SHRs: STZ-CON vs ND-CON (35%). Pioglitazone significantly decreased responses to NA, PE, ME and ANG II in ND-PIO versus ND-CON by 63%. Responses to NA and ANG II were significantly attenuated in STZ-PIO vs. ND-PIO (40%). PPAR-γ regulates systemic hemodynamic in diabetic model and cross-talk relationship exists between PPAR-γ and α1-adrenoceptors, ANG II in systemic vasculature of SHRs.

Assessment of renal function in the anaesthetised rat following injection of superparamagnetic iron oxide nanoparticles

A recent study showed that a significant fall in mean arterial pressure (MAP) occurred following intravenous injection of two novel superparamagnetic iron oxide nanoparticles (SPIONs), MF66 and OD15. To assess if this was caused by excessive glomerular clearance, the effect of both particles on renal function was studied. Experiments were performed on sodium pentobarbital anaesthetised male Wistar rats (250–350 g). Twenty-minute urine clearances were taken followed by an i.v. bolus of MF66, OD15 (2 mg·kg–1), or dH2O (0.4 mL·kg–1). MF6 or OD15 injection resulted in a significant transient drop in MAP and renal blood flow by approximately 33% and 50% (P < 0.05). The absolute excretion of sodium was significantly increased (P < 0.05) by almost 80% and 70% following OD15 and MF66, respectively. Similarly, fractional excretion of sodium was increased by almost 80% and 60% following OD15 and MF66, respectively. The glomerular filtration rate was not significantly affected, but urine flow increased nonsignificantly by approximately 50% and 66% following i.v. injection of OD15 and MF66, respectively. SPIONs produce a decrease in blood pressure and a natriuresis; however, the rate of fluid filtration in the kidney was not significantly affected.

Up Regulation of cystathione γ lyase and Hydrogen Sulphide in the Myocardium Inhibits the Progression of Isoproterenol-Caffeine Induced Left Ventricular Hypertrophy in Wistar Kyoto Rats

Hydrogen sulphide (H2S) is an emerging molecule in many cardiovascular complications but its role in left ventricular hypertrophy (LVH) is unknown. The present study explored the effect of exogenous H2S administration in the regression of LVH by modulating oxidative stress, arterial stiffness and expression of cystathione γ lyase (CSE) in the myocardium. Animals were divided into four groups: Control, LVH, Control-H2S and LVH-H2S. LVH was induced by administering isoprenaline (5mg/kg, every 72 hours, S/C) and caffeine in drinking water (62mg/L) for 2 weeks. Intraperitoneal NaHS, 56μM/kg/day for 5 weeks, was given as an H2S donor. Myocardial expression of Cystathione γ lyase (CSE) mRNA was quantified using real time polymerase chain reaction (qPCR).There was a 3 fold reduction in the expression of myocardial CSE mRNA in LVH but it was up regulated by 7 and 4 fold in the Control-H2S and LVH-H2S myocardium, respectively. Systolic blood pressure, mean arterial pressure, pulse wave velocity were reduced (all P<0.05) in LVH-H2S when compared to the LVH group. Heart, LV weight, myocardial thickness were reduced while LV internal diameter was increased (all P<0.05) in the LVH-H2S when compared to the LVH group. Exogenous administration of H2S in LVH increased superoxide dismutase, glutathione and total antioxidant capacity but significantly reduced (all P<0.05) plasma malanodialdehyde in the LVH-H2S compared to the LVH group. The renal cortical blood perfusion increased by 40% in LVH-H2S as compared to the LVH group. Exogenous administration of H2S suppressed the progression of LVH which was associated with an up regulation of myocardial CSE mRNA/ H2S and a reduction in pulse wave velocity with a blunting of systemic hemodynamic. This CSE/H2S pathway exhibits an antihypertrophic role by antagonizing the hypertrophic actions of angiotensin II(Ang II) and noradrenaline (NA) but attenuates oxidative stress and improves pulse wave velocity which helps to suppress LVH. Exogenous administration of H2S augmented the reduced renal cortical blood perfusion in the LVH state.

Effects of tempol on altered metabolism and renal vascular responsiveness in fructose-fed rats

This study investigated the effect of tempol (a superoxide dismutase mimetic) on renal vasoconstrictor responses to angiotensin II (Ang II) and adrenergic agonists in fructose-fed Sprague–Dawley rats (a model of metabolic syndrome). Rats were fed 20% fructose in drinking water (F) for 8 weeks. One fructose-fed group received tempol (FT) at 1 mmol·L–1 in drinking water for 8 weeks or as an infusion (1.5 mg·kg–1·min–1) intrarenally. At the end of the treatment regimen, the renal responses to noradrenaline, phenylephrine, methoxamine, and Ang II were determined. F rats exhibited hyperinsulinemia, hyperuricemia, hypertriglyceridemia, and hypertension. Tempol reduced blood glucose and insulin levels (all p < 0.05) in FT rats compared with their untreated counterparts. The vasoconstriction response to all agonists was lower in F rats than in control rats by about 35%–65% (all p < 0.05). Vasoconstrictor responses to noradrenaline, phenylephrine, and methoxamine but not Ang II were about 41%–75% higher in FT rats compared with F rats (all p < 0.05). Acute tempol infusion blunted responses to noradrenaline, methoxamine, and Ang II in control rats by 32%, 33%, and 62%, while it blunted responses to noradrenaline and Ang II in F rats by 26% and 32%, respectively (all p < 0.05), compared with their untreated counterparts. Superoxide radicals play a crucial role in controlling renal vascular responses to adrenergic agonists in insulin-resistant rats. Chronic but not acute tempol treatment enhances renal vascular responsiveness in fructose-fed rats.

Enhanced expression of endothelial nitric oxide synthase in the myocardium ameliorates the progression of left ventricular hypertrophy in L-arginine treated Wistar-Kyoto rats

The present study investigated the role of endothelial nitric oxide synthase (eNOS) enzyme in the development of left ventricular hypertrophy (LVH) in Wistar-Kyoto rats. The effect of L-arginine administration on cardiac structure, arterial stiffness, renal and systemic hemodynamic parameters was studied and the change in expression of eNOS and cystathione γ lyase (CSE) in the myocardium of LVH rats was evaluated. LVH was induced using isoprenaline (5 mg/kg, S.C.) and caffeine (62 mg/L in drinking water) for 14 days. Following to that, L-arginine (1.25 g/L in drinking water) was given for 5 weeks as a donor of NO. eNOS and CSE gene expressions were down regulated in the LVH group by about 35% and 67% respectively when compared to control. However, in the LVH group treated with L-arginine there was up regulation of eNOS by almost 27% and down regulation in CSE by 24% when compared to control (all P < 0.05). Heart index and H2S plasma levels were reduced by almost 53% in the L-arginine treated LVH group compared to the control (all P < 0.05). Mean arterial pressure, heart rate and pulse wave velocity were reduced while renal blood perfusion increased in L-arginine treated LVH rats compared to their untreated counterparts (all P < 0.05). The enhanced expression of eNOS in L-arginine treated LVH rats resulted in the amelioration of oxidative and haemodynamic parameters suggesting that NO system is an important therapeutic target in cardiac and LV hypertrophies.

Role of angiotensin AT2 receptors and nitric oxide in the cardiopulmonary baroreflex control of renal sympathetic nerve activity in rats

OBJECTIVES

This study investigated the hypothesis that angiotensin II (type 2) (AT2) receptor activation to modulate the renal sympatho-inhibition to saline volume expansion was dependent on nitric oxide production.

METHODS

Renal sympatho-inhibition to a saline volume expansion (VEP, 0.25% body weight/min i.v. for 30 min) was studied following intracerebroventricular (ICV) saline, CGP42112 (CGP, AT2 agonist), PD123319 (AT2 antagonist), and losartan (AT1 antagonist), and then in combination with N-nitro-L-arginine methyl ester (L-NAME) (nitric oxide synthase inhibitor).

RESULTS

ICV saline, PD123319, CGP, and losartan did not change baseline mean arterial pressure, heart rate, or renal sympathetic nerve activity (RSNA). VEP decreased RSNA in all groups by 58-62% (P<0.05). CGP enhanced the decrease in RSNA compared to saline (74 vs. 60%; P<0.05), whereas PD123319 was without effect (58 vs. 57%). L-NAME only increased baseline RSNA when co-administered with PD123319 (P<0.05). VEP-induced reduction in RSNA following L-NAME was less than during ICV saline (46 vs. 62%; P<0.05). In the group where PD123319 preceded L-NAME, the fall in RSNA was smaller than when PD123319 was infused alone (40 vs. 63%; P<0.05), but not if PD123319 followed L-NAME (52 vs. 44%). L-NAME did not change the magnitude of VEP-induced sympatho-inhibition following CGP (67 vs. 60%). Losartan enhanced the renal sympatho-inhibition to VEP (70 vs. 62%; P<0.05), the magnitude of which was unchanged when L-NAME was present (70 vs. 65%).

CONCLUSION

AT2 receptor activation enhances the VEP-induced reduction in RSNA. Although nitric oxide is important in allowing the normal renal sympatho-inhibitory response to VEP, this is not dependent on AT2 receptors.

The effect of losartan and carvedilol on renal haemodynamics and altered metabolism in fructose-fed Sprague-Dawley rats

The aim of this study is to assess the effects of losartan and carvedilol on metabolic parameters and renal haemodynamic responses to angiotensin II (Ang II) and adrenergic agonists in the model of fructose-fed rat. Thirty-six Sprague-Dawley rats were fed for 8 weeks either 20% fructose solution (F) or tap water (C) ad libitum. F or C group received either losartan or carvedilol (10 mg/kg p.o.) daily for the last 3 weeks of the study (FL and L) and (FCV and CV), respectively, then in acute studies the renal vasoconstrictor actions of Ang II, noradrenaline (NA), phenylephrine (PE) and methoxamine (ME) were determined. Data, mean±SEM were analysed using ANOVA with significance at P <0.05. Losartan and carvedilol decreased the area under the glucose tolerance curve of the fructose-fed group. The responses (%) to NA, PE, ME and Ang II in F were lower (P <0.05) than C (F vs. C, 17±2 vs. 38±3; 24±2 vs. 48±2; 12±2 vs. 34±2; 17±2 vs. 26±2), respectively. L had higher (P <0.05) responses to NA and PE while CV had blunted (P <0.05) responses to NA, PE and Ang II compared to C (L, CV vs. C, 47±3, 9±2 vs. 38±3; 61±3, 29±3 vs. 48±2; 16±3, 4±3 vs. 26±2), respectively. FL but not FCV group had enhanced (P <0.05) responses to NA, PE and ME compared to F (FL vs. F, 33±3 vs. 17±2; 45±3 vs. 24±2; 26±3 vs. 12±2), respectively. Losartan and carvedilol had an important ameliorating effect on fructose-induced insulin resistance. Losartan treatment could be an effective tool to restore normal vascular reactivity in the renal circulation of the fructose-fed rat.

Effect of dragon fruit extract on oxidative stress and aortic stiffness in streptozotocin-induced diabetes in rats

Cardiovascular complications are consistently observed in diabetic patients across all age groups. The objective of the present study was to investigate the effect of aqueous extract of the fruit pulp of Hylocereus undatus (DFE) on aortic stiffness and oxidative stress in streptozotocin (STZ)-induced diabetes in rats. Twenty-four male, Sprague-Dawley rats were randomized into four groups: I (control), II (diabetic), III (DFE, 250 mg/kg) and IV (DFE 500 mg/kg). Diabetes was induced in groups II, III and IV by intraperitoneal (i.p.) injection of STZ (40 mg/kg). After confirmation of diabetes, group III and IV received DFE for 5 weeks. Pulse wave velocity (PWV) was used as a marker of aortic stiffness and was determined at the end of 5 weeks. DFE significantly decreased (P < 0.05) the fasting blood glucose levels in diabetic rats, but not to normal levels. Systolic blood pressure, pulse pressure and PWV were significantly increased (P < 0.05) in diabetic rats at the end of 5 weeks in comparison with control group. DFE treatment significantly decreased (P < 0.05) these elevations. Oxidative damage was observed in group II after 5 weeks. Plasma malondialdehyde levels significantly decreased (P < 0.05), while superoxide dismutase and total antioxidant capacity significantly increased (P < 0.05) with DFE treatment in comparison with group II. These data demonstrate that DFE treatment was effective in controlling oxidative damage and decreasing the aortic stiffness measured by PWV in STZ-induced diabetes in rats.

The Relation between Fructose-Induced Metabolic Syndrome and Altered Renal Haemodynamic and Excretory Function in the Rat

This paper explores the possible relationships between dietary fructose and altered neurohumoral regulation of renal haemodynamic and excretory function in this model of metabolic syndrome. Fructose consumption induces hyperinsulinemia, hypertriglyceridaemia, insulin resistance, and hypertension. The pathogenesis of fructose-induced hypertension is dubious and involves numerous pathways acting both singly and together. In addition, hyperinsulinemia and hypertension contribute significantly to progressive renal disease in fructose-fed rats. Moreover, increased activity of the renin-angiotensin and sympathetic nervous systems leading to downregulation of receptors may be responsible for the blunted vascular sensitivity to angiotensin II and catecholamines, respectively. Various approaches have been suggested to prevent the development of fructose-induced hypertension and/or metabolic alteration. In this paper, we address the role played by the renin-angiotensin and sympathetic nervous systems in the haemodynamic alterations that occur due to prolonged consumption of fructose.

Evidence for the role of α1A-adrenoceptor subtype in the control of renal haemodynamics in fructose-fed Sprague-Dawley rat

AIM

To explore the hypothesis that high fructose intake results in a higher functional contribution of α1A-adrenoceptors and blunts the adrenergically and angiotensin II (Ang II)-induced renal vasoconstriction.

METHODS

Twelve Sprague-Dawley rats received either 20% fructose solution [FFR] or tap water [C] to drink ad libitum for 8 weeks. The renal vasoconstrictor response to noradrenaline (NA), phenylephrine (PE), methoxamine (ME) and Ang II was determined in the presence and absence of 5-methylurapidil (5-MU) (α1A-adrenoceptor antagonist) in a three-phase experiment (pre-drug, low- and high-dose 5-MU). Data, mean ± SEM were analysed by ANOVA or Student's unpaired t-test with significance at P < 0.05.

RESULTS

FFR exhibited insulin resistance (HOMA index), hypertension and significant increases in plasma levels of glucose and insulin. All agonists caused dose-related reductions in cortical blood perfusion that were larger in C than in FFR while the magnitudes of the responses were progressively reduced with increasing doses of 5-MU in both C and FFR. The degree of 5-MU attenuation of the renal cortical vasoconstriction due to NA, ME and Ang II was significantly greater in the FFR compared to C.

CONCLUSIONS

Fructose intake for 8 weeks results in smaller vascular response to adrenergic agonists and Ang II. The α1A-adrenoceptor subtype is the functional subtype that mediates renal cortical vasoconstriction in control rats, and this contribution becomes higher due to fructose feeding.

Effect of renal sympathetic nerve on adrenergically and angiotensin II-induced renal vasoconstriction in normal Wistar-Kyoto rats

BACKGROUND

This study examined the effect of renal sympathetic innervation on adrenergically and angiotensin II (Ang II)-induced renal vasoconstriction in Wistar-Kyoto (WKY) rats.

METHODS

Forty-eight WKY rats were treated with either losartan (10 mg/kg/day p.o.) or carvedilol (5 mg/kg/day p.o.) or a combination of them (10 mg/kg/day + 5 mg/kg/day p.o.) for 7 days. On day 8, the rats were anaesthetized, and renal vasoconstrictor experiments were carried out. A group of rats was subjected to acute unilateral renal denervation during the acute study. Changes in the renal vasoconstrictor responses were determined in terms of reductions in renal blood flow caused by Ang II, noradrenaline (NA), and methoxamine (ME).

RESULTS

In normal animals, losartan decreased (P < 0.05) the renal vasoconstrictor response to Ang II but not to NA or ME. Carvedilol treatment, however, blunted (P < 0.05) the renal vasoconstrictor responses to Ang II and adrenergic agonists. Combination of losartan and carvedilol blunted (P < 0.05) the renal vasoconstrictor response to Ang II but augmented the responses to NA and ME (all P < 0.05). Interestingly, when denervated rats were treated with the same combination, there was a reduction (P < 0.05) in the renal vasoconstrictor responses to Ang II and adrenergic agonists.

CONCLUSIONS

Data suggest that the renal sympathetic nerve contributes to adrenergic agonist-mediated renal vasoconstrictions in normal rats. The data further indicate an interactive relationship between renin-angiotensin and sympathetic nervous systems in modulating adrenergically and Ang II-induced renal vasoconstriction in WKY rats.

The effect of losartan and carvedilol on vasopressor responses to adrenergic agonists and angiotensin II in the systemic circulation of Sprague Dawley rats

1 Interaction between renin-angiotensin (RAS) and sympathetic nervous systems (SNS) was investigated by examining the effect of cumulative blockade of angiotensin II (Ang II) and adrenergic receptors in normal Sprague Dawley rats. 2 Rats were treated with losartan (10 mg/kg), carvedilol (5 mg/kg), or losartan plus carvedilol (10+5 mg/kg) orally for 7 days. On day 8, the animals were anaesthetized with pentobarbitone and prepared for systemic haemodynamic study. Dose-response relationships for the elevation of mean arterial pressure or change in heart rate (HR) in response to intravenous injections of noradrenaline (NA), phenylephrine (PE), methoxamine (ME) and Ang II were determined. 3 Losartan or the combination of losartan with carvedilol blunted vasopressor responses to ME and Ang II. Dose-response relationships for agonist action on HR were significantly inhibited by all treatments except for the combination of losartan and carvedilol on the decrease in HR induced by PE. Carvedilol decreased vasopressor responses to NA, PE and Ang II, and HR responses to NA, ME and Ang II. Combination treatment produced similar effects to losartan on the vasopressor and HR responses but had a greater effect on vasopressor responses to ME and Ang II, and on HR responses to NA and Ang II than carvedilol alone. 4 It is concluded that peripheral vasoconstriction induced by Ang II is partly mediated by adrenergic action and that the vasopressor responses to adrenergic agonists depend on an intact RAS. These observations suggest an interactive relationship between RAS and SNS in determining systemic haemodynamic responses in 'normal' rats.

Influence of sympathetic and AT-receptor blockade on angiotensin II and adrenergic agonist-induced renal vasoconstrictions in spontaneously hypertensive rats

AIM

This study investigated the influence of angiotensin II (Ang II) receptor and adrenergic blockade on the renal vasoconstrictions caused by Ang II and adrenergic agonists in spontaneously hypertensive rats (SHR).

METHODS

Forty-eight SHR were subjected to 7 days of losartan (10 mg kg(-1) day(-1) p.o.), carvedilol (5 mg kg(-1) day(-1) p.o.) or losartan + carvedilol (10 mg kg(-1) day(-1) + 5 mg kg(-1) day(-1) p.o.). On day 8, the rats were anaesthetized and renal vasoconstrictor experiments performed. One group of rats underwent acute unilateral renal denervation.

RESULTS

There were significant (P < 0.05) reductions in the renal vasoconstrictor responses to noradrenaline, phenylephrine, methoxamine and Ang II after losartan and carvedilol treatments compared with that in untreated rats (all P < 0.05). However, in renally denervated SHR treated with carvedilol, the vasoconstrictor responses to all the vasoactive agents were enhanced compared with those in SHR with intact renal nerves treated with carvedilol. Intact SHR given both losartan and carvedilol showed greater renal vasoconstrictor responses to the vasoactive agents than when given either losartan or carvedilol alone (all P < 0.05).

CONCLUSION

Carvedilol reduced the vasoconstrictor response to Ang II and all the adrenergic agonists in the presence of the renal nerves, but, following the removal of renal sympathetic activity, carvedilol enhanced the sensitivity of both renal alpha(1)-adrenoceptors and AT(1) receptors to the vasoactive agents. Co-treatment with losartan and carvedilol reduced the renal vasoconstrictor responses to exogenously administered vasoactive agents but to a lesser extent than losartan or carvedilol alone. The results obtained demonstrate an interaction between Ang II receptors and adrenergic neurotransmission in the SHR.