RESUMEN
Pomolic acid (PA) isolated from Licania pittieri has hypotensive effects in rats, inhibits human platelet aggregation and elicits endothelium-dependent relaxation in rat aortic rings. The present study was designed to investigate the effects of PA on cardiomyocytes. Trabeculae and enzymatically isolated cardiomyocytes from rats were used to evaluate the concentration-dependent effects of PA on cardiac muscle tension and excitation-contraction coupling (ECC) by recording Ca2+ transients reported with Fluo-3 and Fura-2, as well as L-type Ca2+ currents (LTCC). PA reduced the contractile force in rat cardiac trabeculae with an EC50 =â¯14.3⯱â¯2.4⯵M. PA also reduced the amplitude of Ca2+ transients in a concentration-dependent manner, with an EC50 =â¯10.5⯱â¯1.3⯵M, without reducing sarcoplasmic reticulum (SR) Ca2+ loading. PA decreased the half width of the Ca2+ transient by 31.7⯱â¯3.3% and increased the decay time and decay time constant (τ) by 7.6⯱â¯2.7% and 75.6⯱â¯3.7%, respectively, which was associated with increased phospholamban (PLN) phosphorylation. PA also reversibly reduced the macroscopic LTCC in the cardiomyocyte membrane, but did not demonstrate any effects on skeletal muscle ECC. In conclusion, PA reduces LTCC, Ca2+ transients and cardiomyocyte force, which along with its vasorelaxant effects explain its hypotensive properties. Increased PLN phosphorylation protected the SR from Ca2+ depletion. Considering the effects of PA on platelet aggregation and the cardiovascular system, we propose it as a new potential, multitarget cardiovascular agent with a demonstrated safety profile.
Asunto(s)
Acoplamiento Excitación-Contracción/efectos de los fármacos , Contracción Miocárdica/efectos de los fármacos , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Ácido Oleanólico/análogos & derivados , Animales , Canales de Calcio Tipo L/metabolismo , Masculino , Miocitos Cardíacos/citología , NG-Nitroarginina Metil Éster/farmacología , Ácido Oleanólico/farmacología , Fosforilación/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Retículo Sarcoplasmático/efectos de los fármacos , Retículo Sarcoplasmático/metabolismoRESUMEN
Three new lupane-type triterpenoids: 6ß,30-dihydroxybetulinic acid glucopyranosyl ester (4), 6ß,30-dihydroxybetulinic acid (5) and 6ß-hydroxybetulinic acid (6), were isolated from Licania cruegeriana Urb. along with six known compounds. Their structures were elucidated on the basis of spectroscopic methods, including IR, ESIMS, 1D- and 2D-NMR experiments, as well as by comparison of their spectral data with those of related compounds. All compounds were evaluated in vivo for their effects on the mean arterial blood pressure (MABP) and heart rate (HR) of spontaneously hypertensive rats (SHR) and also in vitro for their capacity to inhibit the human platelet aggregation. None of the isolated flavonoids 1-3 showed cardiovascular effects on SHR and among the isolated triterpenoids 4-9 only 5 and 6 produced a significant reduction in MABP (60.1% and 17.2%, respectively) and an elevation in HR (11.0% and 41.2%, respectively). Compounds 3, 4, 5 and 6 were able to inhibit human platelet aggregation induced by ADP, collagen and arachidonic acid with different selectivity profiles.
Asunto(s)
Antihipertensivos/farmacología , Chrysobalanaceae/química , Extractos Vegetales/farmacología , Inhibidores de Agregación Plaquetaria/aislamiento & purificación , Animales , Antihipertensivos/aislamiento & purificación , Presión Arterial/efectos de los fármacos , Flavonoides/aislamiento & purificación , Flavonoides/farmacología , Humanos , Masculino , Extractos Vegetales/aislamiento & purificación , Agregación Plaquetaria/efectos de los fármacos , Inhibidores de Agregación Plaquetaria/farmacología , Ratas Endogámicas SHR , Triterpenos/aislamiento & purificación , Triterpenos/farmacologíaRESUMEN
Pomolic acid has recently shown hypotensive effect in rats. The purpose of this investigation was to determine the vascular effects of this triterpenoid and to examine its mode of action. Functional experiments in rat aortic rings precontracted with norepinephrine were performed to evaluate the vasorelaxant effect of pomolic acid. This triterpenoid induced a vasorelaxation (IC50 = 2.45 µM) in a concentration- and endothelium-dependent manner and showed no effect on contractions evoked by KCl (25 mM). Pre-treatment of aortic rings with L-NAME (100 µM), methylene blue (100 µM) or glibenclamide (10 µM), totally prevented the vasorelaxation induced by pomolic acid, while indomethacin (10 µM) had no effect on this response. Additionally, pomolic acid relaxation was unaffected under the muscarinic- and ß-adrenergic-receptor blocked ensured for atropine and propanolol respectively (10 µM each). In contrast, the vasorelaxant effect of pomolic acid was abolished under the purinergic-receptor blocked ensured for suramin (10 µM). Finally, apyrase (0.8 U/ml) an enzyme which hydrolyses ATP and ADP did not affect pomolic acid relaxation. In summary, pomolic acid has a potent endothelium-dependent vasorelaxant effect, possibly acting through the direct activation of endothelial purinergic receptors via NO-cGMP signaling pathway, which could be part of the mechanism underlying its hypotensive effect.