ABSTRACT
Lectins have been described as glycoproteins that reversibly and specifically bind to carbohydrates. Legume lectins isolated from the subtribe Diocleinae (Canavalia, Dioclea andCratylia) are structurally homologous with respect to their primary structures. The Diocleinae lectins of Canavalia brasiliensis, Dioclea guianensis andCanavalia ensiformis have been shown to distinctly alter physiological parameters in isolated rat kidneys. Thus, the aim of this study was to investigate the effect of Cratylia floribunda lectin (CFL) on renal hemodynamics and ion transport in rats. In isolated perfused kidneys, CFL (10 mg/mL, n=5) increased RPP, RVR and decreased %TK+, but did not change urinary flow, glomerular filtration rate, sodium or chloride tubular transport. In isolated perfused mesenteric bed, CFL (3 and 10 mg/mL/min; n=4) did not alter tissue basal tonus or tissue contraction by phenylephrine (1 mM/mL/min). In conclusion, the seed lectin of Cratylia floribunda increased renal hemodynamic parameters showing a kaliuretic effect. This effect could be of tubular origin, rather than a result from haemodynamic alterations.
As lectinas são descritas como (glico)proteínas que se ligam, especificamente e reversivelmente, a carboidratos. Lectinas de leguminosas isoladas da subtribo Diocleinae (Canavalia, Dioclea eCratylia) são estruturalmente homólogas em relação às suas estruturas primárias. Demonstrou-se que as lectinas de DiocleinaeCanavalia brasiliensis, Dioclea guianensis eCanavalia ensiformis alteram diferentemente parâmetros fisiológicos em rins isolados de ratos. Dessa maneira, o objetivo deste estudo foi investigar o papel da lectina de Cratylia floribunda (CFL) na hemodinâmica renal e no transporte de íons em ratos. Em rins isolados perfundidos, CFL (10 mg/mL, n=5) aumentou a pressão de perfusão renal, a resistência vascular renal e reduziu o percentual do transporte tubular de K+, mas não alterou o fluxo urinário, a taxa de filtração glomerular e o percentual de transporte tubular dos íons sódio e cloreto. No leito mesentérico isolado perfundido, CFL (3 e 10 mg/mL/min, n=4) não alterou o tônus basal ou a contração do tecido induzida por fenilefrina (1 mM/mL/min). Em conclusão, a lectina de sementes de Cratylia floribunda altera parâmetros hemodinâmicos renais, provavelmente de origem tubular, e não por alterações hemodinâmicas.
Subject(s)
Rats , Ion Transport , Plant Lectins/analysis , Dioclea , Hemodynamics , Amiloride/analysisABSTRACT
PURPOSE: The aim of this study was to evaluate the relaxation in vitro of cavernous smooth muscle induced by a new NO donor of the complex nitrosil-ruthenium, named trans-[Ru(NH3)4(caffeine)(NO)]C13 (Rut-Caf) and sodium nitroprusside (SNP). MATERIALS AND METHODS: The tissues, immersed in isolated bath systems, were pre-contracted with phenilephrine (PE) (1 µM) and then concentration-response curves (10-12 - 10-4 M) were obtained. To clarify the mechanism of action involved, it was added to the baths ODQ (10 µM, 30 µM), oxyhemoglobin (10 µM), L-cysteine (100 µM), hydroxicobalamine (100 µM), glibenclamide, iberotoxin and apamine. Tissue samples were frozen in liquid nitrogen to measure the amount of cGMP and cAMP produced. RESULTS: The substances provoked significant relaxation of the cavernous smooth muscle. Both Rut-Caf and SNP determined dose-dependent relaxation with similar potency (pEC50) and maximum effect (Emax). The substances showed activity through activation of the soluble guanylyl cyclase (sGC), because the relaxations were inhibited by ODQ. Oxyhemoglobin significantly diminished the relaxation effect of the substances. L-cysteine failed to modify the relaxations caused by the agents. Hydroxicobalamine significantly diminished the relaxation effect of Rut-Caf. Glibenclamide significantly increased the efficacy of Rut-Caf (pEC50 4.09 x 7.09). There were no alterations of potency or maximum effect of the substances with the addition of the other ion channel blockers. Rut-Caf induced production of significant amounts of cGMP and cAMP during the relaxation process. CONCLUSIONS: In conclusion, Rut-Caf causes relaxation of smooth muscle of corpus cavernosum by means of activation of sGC with intracellular production of cGMP and cAMP; and also by release of NO in the intracellular environment. Rut-Caf releases the NO free radical and it does not act directly on the potassium ion channels.
Subject(s)
Animals , Male , Rabbits , Muscle Relaxation/physiology , Muscle, Smooth/drug effects , Nitric Oxide Donors/pharmacology , Nitroprusside/pharmacology , Ruthenium Compounds/pharmacology , Cyclic GMP/biosynthesis , Cyclic GMP/chemistry , Cysteine/pharmacology , Guanosine Monophosphate/biosynthesis , Guanosine Monophosphate/chemistry , Muscle, Smooth/physiology , Nitric Oxide Donors/chemistry , Nitroprusside/chemistry , Potassium Channels/chemistry , Ruthenium Compounds/chemistry , Time FactorsABSTRACT
O endotélio é um órgão endócrino que regula diversas funções importantes para a homeostase vascular, como tônus, trombogênese, aterogênese, angiogênese, migração celular na inflamação, etc. Esse órgão, como qualquer outro, está sujeito a disfunção e até mesmo falência. Entre os principais fatores de risco que causam disfunção endotelial (DE) estão o diabetes (Db) e a senescência. Neste estudo avaliamos a função endotelial através da medida da resposta relaxante endotélio-dependente em vasos de ratos diabéticos e senescentes e de coelhos diabéticos. A administração oral duas vezes ao dia durante 1 mês de antioxidantes naturais (rutina e ácido lipóico-AL) em ratos diabéticos ou senescente foi capaz de prevenir a DE nestes animais. A taxa de DE na aorta ratos diabéticos tratados apenas com veículo foi de 51,9 +- 4,6% enquanto que nos tratados com rutina foi de 14,1 +- 2,4% (p < 0,05) e 44,7 +- 3,7% nos tratados com AL. No leito arteriolar mesentérico (LAM) dos ratos diabéticos a DE foi de 44,6 +- 5,8% comparado com 21,4 +- 2,8% nos tratados com rutina e 24,8 +- 3,7% no grupo tratado com AL. O mesmo padrão de resposta foi observado no leito vascular renal (LVR) corpos cavernosos de coelhos (RbCC) diabéticos. Nestes tecidos a incubação por 1 hora com 1 μM de rutina ou AL foi capaz de reverter a DE. No LVR a resposta relaxante máxima à acetilcolina (ACh) foi de 16,0 +- 2,0% comparada com 42,0 +- 3,4% obtidas nos LVR tratados com rutina e 31,0 +- 3,9% nos tratados com AL...