Effect Of Changbai Mountain Radix Astragali On Atrial Dynamics And ANP Secretion

As an endocrine gland,the heart generates and secretes natriuretic peptides hormone. Natriuretic peptides were stored in human and mammal as family of natriuretic peptides (NPs) forming,members in NPs including ANP(atrial natriuretic peptide,ANP),BNP (brain natriuretic peptide,BNP),CNP(C-type natriuretic peptide,CNP) and DNP (dendroaspis natriuretic peptide,DNP).It was known that all of the NPs members involved in important biological effects such as diuresis and natriuresis,regulating body fluid and blood pressure,irdaibition of cellular proliferation,regulating immunization, protecting cell and lipolysis by combining with natriuretic peptide receptors which were distributed in the heart,blood vessel,central nervous system,lymph tissue,reproductive organs and kidney.ANP was discovered by De Bold et al(1981) in the atrium.It was demonstrated that many factors involved in the regulation of atrial ANP secretion.Atrial swelling or rising atrial pulse pressure had been related with ANP secretion.Humoral factors also been contributed in atrial ANP secretion.In addition,the roles of adrenergic,cholinergic and peptidergic regulation of ANP release are controversial.However,atrial stretch had been considered as a critical stimulator for atrial ANP secretion.Radix Astragali was first recorded by "Shennong Herbal" and was considered as an important herbal on invigorating vital energy in traditional Chinese medicine.The natural Radix Astragali is sweet flavor and microtherm.The major components of Radix Astragali are including Radix Astragali saponin,astragalus polysaccharides,flavanoid et al.It was known that Radix Astragali play several important pharmacological actions such as increase cardiac dynamoics,anti-tiredness,relax aeteria coronaria and arteria renalis,improve dermato-circulation and regulate blood pressure,However,the mechanicsm of that Radix Astragali-induced cardiac positive inotropic effect is controversial.In addition,the effect of Radix Astragali on atrial ANP secretion is not clear.So the purpose of the present study is to define the effect and the mechanism of Changbai mountain Radix Astragali(CMRA) atrail dynamics and ANP secretion in perfused beating rabbit atria.The results of the present study showed that:1.CMRA(2.0mg/ml,2.5mg/ml and 3.0mg/ml) significantly increased atrial stroke volume(under 2.0mg/ml P＜0.05 vs control cycle;under 2.5mg/ml P＜0.01 vs control cycle;under 3.0mg/ml P＜0.001 vs control cycle respectively) and atrial pulse pressure (P＜0.001 vs control cycle respectively) with dose-dependent manner.The most effect of CMRA on the atrial dynamics was observed in 2.Smg/ml.2.CMRA 2.5mg/ml) inhibited atrial ANP secretion(P＜0.001 vs control cycle) concomitantly with increased atrial stroke volume and pulse pressure(P＜0.001 vs control cycle respectively).3.KB-R 7943(10μmol/L),an inhibitor of reversed Na⁺-Ca²⁺/exchanger,blocked the effect of CMRA on atrial dynamics(P＜0.05 vs control cycle respectively);Whereas the KB-R 7943 failed to modulation of CMRA-inhibited atrial ANP secretion(P＜0.001 vs control cycle).4.Nifedipine,an L-type Ca²⁺ channel inhibitor,showed negative inotropism on the atrial dynamics and blocked the effect of CMRA(2.5mg/ml)-augmented atrial dynamics (P＜0.001 vs control cycle).Simultaneously,nifedipine(1.0μmol/L) failed to modulation of CMRA-induced inhibition of atrial ANP secretion(P＜0.001 vs control cycle).These results indicate that:1.CMRA may increases atrial dynamics by dose-dependent manner in perfused beating rabbit atria via Na⁺-Ca²⁺/exchanger and L-type Ca²⁺ channels;2.CMRA negatively modulates ANP secretion in beating rabbit atria.