Antihypertensive Potential of Tartaric Acid and Exploration of Underlying Mechanistic Pathways

Tartaric acid is capable of balancing blood pressure. It is the main constituent of antihypertensive agents (grapes and wine) and has not been scientifically explored as an antihypertensive remedy. This study aimed to investigate the antihypertensive effect of a low-dose tartaric acid in vivo and explore underlying mechanisms in vitro. Intravenous administration of tartaric acid at the dose of 50 mu g/kg caused a % fall in mean arterial pressure (MAP) in normotensive and hypertensive rats [51.5 +/- 1.7 and 63.5 +/- 2.9% mmHg]. This hypotensive effect was partially inhibited by atropine (1 mg/kg) and (L)-NAME (100 mu g/kg) pretreatment. In hypertensive rats, oral administration of tartaric acid (.1, .5, 1, 5, and 10 mg/kg) for 2 weeks resulted in 65 +/- 7.3 mmHg MAP at 10 mg/kg. This antihypertensive effect was comparable to the orally administered verapamil (10 mg/kg) for 2 weeks which caused a decrease in MAP 60.4 +/- 3.8 mmHg. Tartaric acid relaxed phenylephrine (PE) and High K+-induced contractions with EC50 values of .157 (.043-.2) and 1.93 (.07-2) mu g/mL in vitro. This endothelium-dependent relaxation was inhibited with atropine (1 mu M) and (L)-NAME (10 mu M) pretreatment. Tartaric acid also suppressed phenylephrine contractions in Ca+2 free/EGTA medium and on voltage-dependent calcium channels, causing the concentration-response curves toward right. Tartaric acid induced negative inotropic and chronotropic effects with EC50 values of .26 (.14-.4) and .60 (.2-.8) in rat atria. It showed its effect by complete blockade against atropine and partially in propranolol pretreatment. These findings provide scientific basis to low-dose tartaric acid as an antihypertensive and vasodilatory remedy through muscarinic receptor-linked nitric oxide (NO) pathway and Ca+2 channel antagonist.