CHLOROGENIC ACID CAN INHIBIT CATECHOLAMINE SECRETION FROM THE ADRENAL MEDULLA

Abstract

Objective: Chlorogenic acid (CGA) is one of the most available phenolic acid compounds in foods, such as coffee and tea, which is known to be the most effective agent in lowering blood pressure and helpful in treating hypertension-related disorders. Thus the present study was aimed to determine the characteristics of CGA on secretion of catecholamines (CA) in the perfused model of the rat adrenal medulla, and also to validify its mechanism of action. Design and method: he adrenal gland was isolated and perfused with Krebs-bicarbonate. CA was measured directly by using the fluorospectrophotometer. Results: CGA, administered into an adrenal vein for 90 min, reduced ACh -induced CA secretion in a dose- and time-dependent manner. CGA also time-dependently depressed the CA secretion induced by McN-A-343, DMPP, and angiotensin II . CGA itself failed to influence spontaneous CA secretion. Also, During the perfusion of CGA for 90 min, the CA secretory responses induced by high K+, veratridine, cyclopiazonic acid, Bay-K-8644 were suppressed. However, in the simultaneous presence of CGA and L-NAME, the CA secretory responses induced by ACh, Ang II, Bay-K-8644 and veratridine was restored nearly to the control level compared to those of the inhibitory effects of CGA-treatment alone. Virtually, the adrenal NO release was significantly enhanced by CGA-treatment. Also, in the coexistence of CGA and olmesartan, ACh-induced CA secretion was markedly reduced compared to that of olmesartan-treatment alone. Conclusions: Taken together, we present the first evidence that CGA suppresses the CA secretion induced by activation of cholinoceptors as well as AT1-receptors. This CGA-induced inhibitory effect seems to be exerted by reducing both the influx of Na+ and Ca2+ through their ionic channels into adrenomedullary chromaffin cells as well as by suppressing the Ca2+ release from the cytoplasmic calcium store, through the elevated NO release by the activation of NO synthase, which is associated to the blockade of neuronal cholinonoceptors and AT1-receptors. Based on these results, the ingestion of CGA may be helpful to alleviate or prevent the cardiovascular diseases, via reduction of adrenal CA secretion and consequent decreased CA level in circulation.