A high-fat meal impairs muscle vasodilatation response to mental stress in humans with Glu27 beta(2)-adrenoceptor polymorphism

Background: Forearm blood flow responses during mental stress are greater in individuals homozygous for the Glu27 allele. A high-fat meal is associated with impaired endothelium-dependent dilatation. We investigated the impact of high-fat ingestion on the muscle vasodilatory responses during mental stress in individuals with the Glu27 allele and those with the Gln27 allele of the beta(2)-adrenoceptor gene. Methods: A total of 162 preselected individuals were genotyped for the Glu27Gln beta(2)-adrenoceptor polymorphism. Twenty-four individuals participated in the study. Fourteen were homozygous for the Gln27 allele (Gln27Gln, 40 +/- 2 years; 64 +/- 2 kg), and 10 were homozygous for the Glu27 allele (Glu27Glu, 40 +/- 3 years; 65 +/- 3 kg). Forearm blood flow was evaluated by venous occlusion plethysmography before and after ingestion of 62 g of fat. Results: The high-fat meal caused no changes in baseline forearm vascular conductance (FVC, 2.2 +/- 0.1 vs. 2.4 +/- 0.2; P = 0.27, respectively), but reduced FVC responses to mental stress (1.5 +/- 0.2 vs. 0.8 +/- 0.2 units; P = 0.04). When volunteers were divided according to their genotypes, baseline FVC was not different between groups (Glu27Glu = 2.4 +/- 0.1 vs. Gln27Gln = 2.1 +/- 0.1 units; P = 0.08), but it was significantly greater in Glu27Glu individuals during mental stress (1.9 +/- 0.4 vs. 1.0 +/- 0.3 units; P = 0.04). High-fat intake eliminated the difference in FVC responses between Glu27Glu and Gln27Gln individuals (FVC, 1.3 +/- 0.4 vs. 1.2 +/- 0.4; P = 0.66, respectively). Conclusion: These findings demonstrate that a high-fat meal impairs muscle vasodilatation responses to mental stress in humans. However, this reduction can be attributed to the presence of the homozygous Glu27 allele of the beta(2)-adrenoceptor gene.

Glu298Asp eNOS gene polymorphism causes attenuation in nonexercising muscle vasodilatation

Dias RG, Alves MJ, Pereira AC, Rondon MU, dos Santos MR, Krieger JE, Krieger MH, Negrao CE. Glu298Asp eNOS gene polymorphism causes attenuation in nonexercising muscle vasodilatation. Physiol Genomics 37: 99-107, 2009. First published January 21, 2009; doi:10.1152/physiolgenomics.90368.2008.-The influence of Glu298Asp endothelial nitric oxide synthase (eNOS) polymorphism in exercise-induced reflex muscle vasodilatation is unknown. We hypothesized that nonexercising forearm blood flow (FBF) responses during handgrip isometric exercise would be attenuated in individuals carrying the Asp298 allele. In addition, these responses would be mediated by reduced eNOS function and NO-mediated vasodilatation or sympathetic vasoconstriction. From 287 volunteers previously genotyped, we selected 33 healthy individuals to represent three genotypes: Glu/Glu [n = 15, age 43 +/- 3 yr, body mass index (BMI) 22.9 +/- 0.3 kg/m(2)], Glu/Asp (n = 9, age 41 +/- 3 yr, BMI 23.7 +/- 1.0 kg/m(2)), and Asp/Asp (n = 9, age 40 +/- 4 yr, BMI 23.5 +/- 0.9 kg/m(2)). Heart rate (HR), mean blood pressure (MBP), and FBF (plethysmography) were recorded for 3 min at baseline and 3 min during isometric handgrip exercise. Baseline HR, MBP, FBF, and forearm vascular conductance (FVC) were similar among genotypes. FVC responses to exercise were significantly lower in Asp/Asp when compared with Glu/Asp and Glu/Glu (Delta = 0.07 +/- 0.14 vs. 0.64 +/- 0.20 and 0.57 +/- 0.09 units, respectively; P = 0.002). Further studies showed that intra-arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA) did not change FVC responses to exercise in Asp/Asp, but significantly reduced FVC in Glu/Glu (Delta = 0.79 +/- 0.14 vs. 0.14 +/- 0.09 units). Thus the differences between Glu/Glu and Asp/Asp were no longer observed (P = 0.62). L-NMMA + phentolamine increased similarly FVC responses to exercise in Glu/Glu and Asp/Asp (P = 0.43). MBP and muscle sympathetic nerve activity increased significant and similarly throughout experimental protocols in Glu/Glu and Asp/Asp. Individuals who are homozygous for the Asp298 allele of the eNOS enzyme have attenuated nonexercising muscle vasodilatation in response to exercise. This genotype difference is due to reduced eNOS function and NO-mediated vasodilatation, but not sympathetic vasoconstriction.

Repetitive brief ischemia: Intermittent reperfusion during ischemia ameliorates the extent of injury in the perfused kidney

Acute renal failure commonly follows reduced renal perfusion or ischemia. Reperfusion is essential for recovery but can itself cause functional and structural injury to the kidney. The separate contributions of ischemia and of reperfusion were examined in the isolated perfused rat kidney. Three groups were studied: brief (5 min) ischemia, 20 min ischemia, and repetitive brief ischemia (4 periods of 5 min) with repetitive intervening reperfusion of 5 min. A control group had no intervention, the three ischemia groups were given a baseline perfusion of 30 min before intervention and all groups were perfused for a total of 80 min. In addition, the effects of exogenous (NO)-N-. from sodium nitroprusside and xanthine oxidase inhibition by allopurinol were assessed in the repetitive brief ischemia-reperfusion model. Brief ischemia produced minimal morphological injury with near normal functional recovery. Repetitive brief ischemia reperfusion caused less functional and morphological injury than an equivalent single period of ischemia (20 min) suggesting that intermittent reperfusion is less injurious than ischemia alone over the time course of study. Pretreatment with allopurinol improved renal function after repetitive brief ischemia-reperfusion compared with the allopurinol-untreated repetitive brief ischemia-reperfusion group. Similarly, sodium nitroprusside reduced renal vascular resistance but did not improve the glomerular filtration rate or sodium reabsorption in the repetitive brief ischemia-reperfusion model. Thus, these studies show that the duration of uninterrupted ischemia is more critical than reperfusion in determining the extent of renal ischemia-reperfusion injury and that allopurinol, in particular, counteracts the oxidative stress of reperfusion.

Torasemide is an effective diuretic in the newborn rabbit.

The effect of intravenous (i.v.) torasemide on diuresis and renal function was evaluated in three groups of normoxemic, 5- to 10-day-old, newborn New Zealand White rabbits. The animals of group 1 received 0.2 mg/kg of torasemide i.v., whereas in group 2 an i.v. dose of 1.0 mg/kg was given. The third group of animals received a bolus i.v. dose of 1.0 mg/kg torasemide with continuous i.v. replacement of estimated urinary fluid and electrolyte losses. Torasemide proved to be an effective, potassium-sparing diuretic, without significant effect on glomerular filtration rate (GFR). Renal blood flow (RBF) fell and the renal vascular resistance (RVR) rose in all three groups of animals, although the rise in RVR in group 3 was not significant. These changes in renal hemodynamics were most pronounced in the animals of group 2 and are probably secondary to torasemide-induced hypovolemia (2.8% loss of body weight) and accompanying humoral reactions, such as an increase in angiotensin II (not measured). When the latter is prevented by simultaneous re-infusion of an electrolyte solution (group 3), replacing urinary losses, GFR increases and the changes in RBF and RVR are blunted. We conclude that torasemide is an effective, potassium-sparing diuretic in newborn rabbits. No evidence was found for a vasodilatory action of the drug.

Effects of microcystin-LR in isolated perfused rat kidney

Microcystin is a hepatotoxic peptide which inhibits protein phosphatase types 1 and 2A. The objective of the present study was to evaluate the physiopathologic effects of microcystin-LR in isolated perfused rat kidney. Adult Wistar rats (N = 5) of both sexes (240-280 g) were utilized. Microcystin-LR (1 µg/ml) was perfused over a period of 120 min, during which samples of urine and perfusate were collected at 10-min intervals to determine the levels of inulin, sodium, potassium and osmolality. We observed a significant increase in urinary flow with a peak effect at 90 min (control (C) = 0.20 ± 0.01 and treated (T) = 0.32 ± 0.01 ml g-1 min-1, P<0.05). At 90 min there was a significant increase in perfusate pressure (C = 129.7 ± 4.81 and T = 175.0 ± 1.15 mmHg) and glomerular filtration rate (C = 0.66 ± 0.07 and T = 1.10 ± 0.04 ml g-1 min-1) and there was a significant reduction in fractional sodium tubular transport at 120 min (C = 78.6 ± 0.98 and T = 73.9 ± 0.95%). Histopathologic analysis of the perfused kidneys showed protein material in the urinary space, suggestive of renal toxicity. These data demonstrate renal vascular, glomerular and urinary effects of microcystin-LR, indicating that microcystin acts directly on the kidney by probable inhibition of protein phosphatases.

Subacute effects of a maximal exercise bout on endothelium-mediated vasodilation in healthy subjects

We evaluated vascular reactivity after a maximal exercise test in order to determine whether the effect of exercise on the circulation persists even after interruption of the exercise. Eleven healthy sedentary volunteers (six women, age 28 ± 5 years) were evaluated before and after (10, 60, and 120 min) a maximal exercise test on a treadmill. Forearm blood flow (FBF) was measured by venous occlusion plethysmography before and during reactive hyperemia (RH). Baseline FBF, analyzed by the area under the curve, increased only at 10 min after exercise (P = 0.01). FBF in response to RH increased both at 10 and 60 min vs baseline (P = 0.004). Total excess flow for RH above baseline showed that vascular reactivity was increased up to 60 min after exercise (mean ± SEM, before: 526.4 ± 48.8; 10 min: 1053.0 ± 168.2; 60 min: 659.4 ± 44.1 ml 100 ml-1 min-1 . s; P = 0.01 and 0.02, respectively, vs before exercise). The changes in FBF were due to increased vascular conductance since mean arterial blood pressure did not change. In a time control group (N = 5, 34 ± 3 years, three women) that did not exercise, FBF and RH did not change significantly (P = 0.07 and 0.7, respectively). These results suggest that the increased vascular reactivity caused by chronic exercise may result, at least in part, from a summation of the subacute effects of successive exercise bouts.

Effects of diet and exercise training on neurovascular control during mental stress in obese women

Since neurovascular control is altered in obese subjects, we hypothesized that weight loss by diet (D) or diet plus exercise training (D + ET) would improve neurovascular control during mental stress in obese women. In a study with a dietary reduction of 600 kcal/day with or without exercise training for 4 months, 53 obese women were subdivided in D (N = 22, 33 ± 1 years, BMI 34 ± 1 kg/m²), D + ET (N = 22, 33 ± 1 years, BMI 33 ± 1 kg/m²), and nonadherent (NA, N = 9, 35 ± 2 years, BMI 33 ± 1 kg/m²) groups. Muscle sympathetic nerve activity (MSNA) was measured by microneurography and forearm blood flow by venous occlusion plethysmography. Mental stress was elicited by a 3-min Stroop color word test. Weight loss was similar between D and D + ET groups (87 ± 2 vs 79 ± 2 and 85 ± 2 vs 76 ± 2 kg, respectively, P < 0.05) with a significant reduction in MSNA during mental stress (58 ± 2 vs 50 ± 2, P = 0.0001, and 59 ± 3 vs 50 ± 2 bursts/100 beats, P = 0.0001, respectively), although the magnitude of the response was unchanged. Forearm vascular conductance during mental stress was significantly increased only in D + ET (2.74 ± 0.22 vs 3.52 ± 0.19 units, P = 0.02). Weight loss reduces MSNA during mental stress in obese women. The increase in forearm vascular conductance after weight loss provides convincing evidence for D + ET interventions as a nonpharmacologic therapy of human obesity.

Examining the roles of core and local temperature on forearm skin blood flow

The interaction between local and reflexive control of skin blood flow (SkBF) is unclear. This thesis isolated the roles of rectal (Tre) and local (Tloc) temperature on forearm SkBF regulation at normal and elevated body temperatures, and to investigate the interaction between local and reflexive SkBF control. While either normothermic (Tre ~37.0°C) or hyperthermic (∆Tre +1.1°C), SkBF was assessed on the dorsal aspect of each forearm in 10 participants while Tloc was manipulated in an A-B-A-B fashion between neutral (33.0°C) and hot (38.5°C). Finally, local heating to 44°C was performed to elicit maximal SkBF. Data are presented as a percentage of maximal cutaneous vascular conductance (CVC), calculated as laser-Doppler flux divided by mean arterial pressure. Tloc manipulations performed during normothermia had significantly greater effects on CVC than during hyperthermia. The decreased modification to SkBF from the Tloc changes during hyperthermia suggests that strong reflexive vasodilation attenuates local SkBF control mechanisms.

Systemic and regional hemodynamics in pigs with acute liver failure and the effect of albumin dialysis.

OBJECTIVE: Acute liver failure (ALF) is haemodynamically characterized by a hyperdynamic circulation. The aims of this study were to investigate the systemic and regional haemodynamics in ALF, to measure changes in nitric oxide metabolites (NOx) and to evaluate whether these haemodynamic disturbances could be attenuated with albumin dialysis. MATERIAL AND METHODS: Norwegian Landrace pigs (23-30 kg) were randomly allocated to groups as controls (sham-operation, n = 8), ALF (hepatic devascularization, n = 8) and ALF + albumin dialysis (n = 8). Albumin dialysis was started 2 h after ALF induction and continued for 4 h. Systemic and regional haemodynamics were monitored. Creatinine clearance, nitrite/nitrate and catecholamines were measured. A repeated measures ANOVA was used to analyse the data. RESULTS: In the ALF group, the cardiac index increased (PGT < 0.0001), while mean arterial pressure (PG = 0.02) and systemic vascular resistance decreased (PGT < 0.0001). Renal resistance (PG = 0.04) and hind-leg resistance (PGT = 0.003) decreased in ALF. There was no difference in jejunal blood flow between the groups. ALF pigs developed renal dysfunction with increased serum creatinine (PGT = 0.002) and decreased creatinine clearance (P = 0.02). Catecholamines were significantly higher in ALF, but NOx levels were not different. Albumin dialysis did not attenuate these haemodynamic or renal disturbances. CONCLUSIONS: The haemodynamic disturbances during the early phase of ALF are characterized by progressive systemic vasodilatation with no associated changes in metabolites of NO. Renal vascular resistance decreased and renal dysfunction developed independently of changes in renal blood flow. After 4 h of albumin dialysis there was no attenuation of the haemodynamic or renal disturbances.

Implicaciones clínicas y quirúrgicas de las variaciones anatómicas vasculares del riñón

Introducción: Conocer y diagnosticar las variaciones más frecuentes de la vasculatura renal es de gran importancia para la planificación de la nefrectomía laparoscópica en el donante y para la reconstrucción vascular en el trasplante renal. De igual forma, considerar las variaciones vasculares −especialmente las del sistema venoso− es indispensable en reconstrucción vascular debido a la gran proporción de variaciones venosas asociadas a aneurismas de la aorta abdominal; además, es ideal en el estudio de condiciones clínicas tales como el síndrome de congestión pélvica y la hematuria. Metodología: Se trata de una revisión de la bibliografía sobre la proporción, diagnóstico, procedimientos quirúrgicos y síndromes clínicos asociados a las variaciones de la vasculatura renal, basada en el material encontrado con la siguiente estrategia de búsqueda: “Renal Artery/abnormalities”[Mesh] OR Renal Veins/abnormalities”[Mesh] AND “surgery”[Mesh] OR “transplantation”[Mesh] OR “radiography”[Mesh] “Kidney Pelvis/abnormalities”[Mesh] AND “Kidney Pelvis/blood supply”[Mesh]. Esta estrategia se modificó de acuerdo con las bases de datos: MEDLINE/PubMed, MEDLINE OVID, SCIENCEDIRECT, HINARI y LILACS. Desarrollo: Se revisó el origen y los tipos más frecuentes de variaciones de la vasculatura renal. Se investigó sobre las implicaciones quirúrgicas y los síndromes clínicos asociados.

Purification and characterization of the biological effects of phospholipase A(2) from sea anemone Bunodosoma caissarum

Sea anemones contain a variety of biologically active substances. Bunodosoma caissarum is a sea anemone from the Cnidaria phylum, found only in Brazilian coastal waters. The aim of the present work was to study the biological effects of PLA(2) isolated from the sea anemone B. caissarum on the isolated perfused kidney, the arteriolar mesenteric bed and on insulin secretion. Specimens of B. caissarum were collected from the Sao Vicente Channel on the southern coast of the State of São Paulo, Brazil. Reverse phase HPLC analysis of the crude extract of B. caissarum detected three PLA(2) proteins (named BcPLA(2)1, BCPLA(2)2 and BcPLA(2)3) found to be active in B. caissarum extracts. MALDI-TOF mass spectrometry of BcPLA(2)1 showed one main peak at 14.7 kDa. The N-terminal amino acid sequence of BcPLA(2)1 showed high amino acid sequence identity with PLA(2) group III protein isolated from the Mexican lizard (PA23 HELSU, HELSU, PA22 HELSU) and with the honey bee Apis mellifera (PLA(2) and 1POC_A). In addition, BcPLA(2)1 also showed significant overall homology to bee PLA(2). The enzymatic activity induced by native BCPLA(2)1 (20 mu g/well) was reduced by chemical treatment with p-bromophenacyl bromide (p-BPB) and with morin. BcPLA(2)1 strongly induced insulin secretion in presence of high glucose concentration. In isolated kidney, the PLA(2) from B. caissarum increased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate, and sodium, potassium and chloride levels of excretion. BcPLA(2)1, however, did not increase the perfusion pressure on the mesenteric vascular bed. In conclusion, PLA(2), a group III phospholipase isolated from the sea anemone B. caissarum, exerted effects on renal function and induced insulin secretion in conditions of high glucose concentration. (C) 2009 Elsevier Ltd. All rights reserved.

Purification and biological effects of a C-type lectin isolated from Bothrops moojeni

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cardiovascular actions of rattlesnake bradykinin ([Val(1), Thr(6)] bradykinin) in the anesthetized South American rattlesnake Crotalus durissus terrificus

Incubation of heat-denatured plasma from the rattlesnake Crotalus atrox with trypsin generated a bradykinin (BK) that contained two amino acid substitutions (Arg(1) --> Val and Ser(6) --> Thr) compared with mammalian BK. Bolus intra-arterial injections of synthetic rattlesnake BK (0.01-10 nmol/kg) into the anesthetized rattlesnake, Crotalus durissus terrificus, produced a pronounced and concentration-dependent increase in systemic vascular conductance (Gsys). This caused a fall in systemic arterial blood pressure (Psys) and an increase in blood flow. Heart rate and stroke volume also increased. This primary response was followed by a significant rise in Psys and pronounced tachycardia (secondary response). Pretreatment with N-G-nitro-L-arginine methyl ester reduced the NK-induced systemic vasodilatation, indicating that the effect is mediated through increased NO synthesis. The tachycardia associated with the late primary and secondary response to BK was abolished with propranolol and the systemic vasodilatation produced in the primary phase was also significantly attenuated by pretreatment, indicating that the responses are caused, at least in part, by release of cathecholamines and subsequent stimulation of beta-adrenergic receptors. In contrast, the pulmonary circulation was relatively unresponsive to BK.

Efeitos renais e cardiovasculares da infusão de dopamina e da solução de cloreto de sódio a 7,5%: estudo experimental em cães com restrição hídrica

JUSTIFICATIVA E OBJETIVOS: É controvertido o uso da infusão de dopamina na proteção renal. O objetivo desta pesquisa foi estudar o efeito da dopamina, da solução hipertônica e da associação de ambas em cães com restrição hídrica, simulando o jejum pré-operatório. MÉTODO: Foram estudados, em 32 cães anestesiados com tiopental sódico e fentanil, os seguintes parâmetros da função renal: fluxo plasmático efetivo renal (depuração de para-aminohipurato de sódio), ritmo de filtração glomerular (depuração de creatinina) e as depurações de sódio, de potássio e osmolar, excreção fracionária de sódio e potássio, excreção de sódio e potássio e a resistência vascular renal. Os parâmetros cardiovasculares foram: pressão arterial média, freqüência cardíaca, pressão da veia cava inferior, índice cardíaco, hematócrito e índice de resistência vascular periférica. Os animais foram subdivididos, através de sorteio, em 4 grupos experimentais: Grupo 1 - G1 (n = 8) - grupo controle; Grupo 2 - G2 (n = 8) infusão de dopamina (2 µg.kg-1.min-1), Grupo 3 - G3 (n = 8) solução de cloreto de sódio a 7,5% (2 ml.kg-1) e Grupo 4 - G4 (n = 8) - associação de dopamina (2 µg.kg-1.min-1) e cloreto de sódio a 7,5% (2 ml.kg-1). Os grupos tiveram quatro fases experimentais e cada momento com duração de 30 minutos, compreendendo os momentos M1, M2, M3 e M4. RESULTADOS: O grupo da dopamina (G2) apresentou diminuição da pressão arterial média, da resistência vascular renal e da excreção de potássio. O grupo da solução hipertônica de cloreto de sódio (G3) apresentou aumento do índice cardíaco, do volume urinário, da depuração de sódio e de potássio, da excreção urinária de sódio e potássio e da excreção fracionária de sódio. No grupo da solução hipertônica de cloreto de sódio associada à dopamina (G4), ocorreu elevação da freqüência cardíaca, do índice cardíaco, do fluxo plasmático efetivo renal e da excreção urinária de sódio; ocorreu também diminuição do índice de resistência vascular sistêmica e do potássio plasmático. CONCLUSÕES: Deste estudo conclui-se que a solução hipertônica de cloreto de sódio foi capaz de melhorar as condições hemodinâmicas e, conseqüentemente, a função renal de cães sob restrição hídrica de 12 horas. O mesmo não aconteceu com a infusão de 2 µg.kg-1.min-1 de dopamina que, em situação similar, não causou aumento da diurese e da excreção de sódio.

Efeitos do pneumoperitônio sobre a hemodinâmica e função renais de cães ventilados com volume e pressão controlados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)