Hypotensive effect of yeast in the hypertensive rat model

Abstract

Elevated arterial blood pressure is the most important public health problem in developed countries. It often leads to lethal complications  if left untreated. Brewer's yeast is celebrated for its various beneficial effects, including a possible hypotensive effect.  Thus, the anti-hypertensive effects of brewer’s yeast were investigated. The hypertensive model was done by a once-weekly  intraperitoneal injection of dexamethasone at a dose of 25 mg/kg combined with drinking a 1.0% sodium chloride solution containing  0.2% KCl and 2.0% glucose for six weeks. The blood pressure was measured by the rat carotid artery cannulation preparation. Different  doses of brewer's yeast dissolved in distilled water were injected into the internal jugular vein, with measurement of blood pressure at  each time. To explore the mechanism of the hypotensive effect of yeast, the yeast cardiac effect was verified by the use of isolated  perfused rabbit heart preparations using different antagonists. It was found that dexamethasone elevated systolic blood pressure to  178.3±11.6 and diastolic blood pressure to 133.3±16.6 from normal levels of 115.0±9.1 for systolic and 74.0±4.1 for diastolic. The gradual  increase in intravenous yeast doses ranging from 0.05 to 0.40 effectively lowered systolic and diastolic blood pressure in rats with normal  pressure, bringing them to approximately 80.0±05.6 mmHg for systolic and 40.0±3.5 mmHg for diastolic. While doses exceeding 0.04  resulted in a drop in systolic pressure to 60.0±3.9 mmHg, diastolic pressure became unrecordable. The administration of the 0.20 dose  resulted in unrecordable blood pressure. In hypertensive rats, a decrease in blood pressure was observed with doses ranging from  0.60-1.0 mg, leading to a reduction to 110.0±2.8 mmHg for systolic and 52.0±9.9 mmHg for diastolic pressures. Doses exceeding 1.0 mg  further lowered systolic and diastolic pressures to 20.0±3.9 mmHg. There was a mild increase in heart rate with no change in cardiac force  of contraction. This effect was not mediated through beta, calcium receptors, or the histamine effect. The findings show that the  yeast has a dose-dependent blood pressure-lowering effect. The mechanism of the chronotropic effect is possibly due to its direct action.