Effects of quercetin and naringenin on rate and force of contraction of isolated rat right and left atria

Abstract

Flavonoids have been known for their cardiotonic actions. This study investigated the effects of quercetin and naringenin, one of the most abundant dietary flavonoids, on rate and contraction of isolated rat atria. The right and left atria were isolated from male Wistar rats (250 300g), attached to force transducer and suspended in a 20 ml - organ bath containing Krebs-Henseleit solution at 37 degrees celsius, gassed with carbogen. The results showed that these two flavonoids elicited different cardiotonic activities. Quercetin (100 micrometre) increased the contraction of the right and left atria by 33.32 +- 4.13 % and 45.75 +- 4.90%, respectively. In addition, it caused an increased in the rate of the right atria by 17.62 +- 6.51%. In contrast, naringenin (100 micrometre) slightly decreased the contraction of the right and left atria by 6.16 +- 3.02 % and 10 +- 3.51%, respectively. It also markedly reduced the rate of right atria by 30% +- 5.32 %. Quercetin possessed intrinsic inotropic activity which did not relate to a release of synaptic catecholamine. Moreover, the positive inotropic effect of quercetin was blocked by propranolol (10 micrometre), verapamil (1 micrometre) and pinacidil (100 micrometre). The negative inotropic property of naringenin was not change in the presence of atropine (10 micrometre) and pinacidil (100 micrometre). Furthermore, the actions of both flavonoids were not related to Ca[superscript 2+] release from SR. The positive inotropic effect of quercetin may be due to the activation of beta-adrenoceptor, an increase Ca[superscript 2+] influx. In addition, quercetin may interfere function of K[superscript +] channel. Furthermore, naringenin caused the negative inotropic and chronotropic effects of which were not related cholinergic receptor. In conclusions, quercetin and naringenin exerted their cardiotonic actions on pacemaker and cardiac muscle.