Influence of Ginkgo biloba extract feeding on blood pressure, heart rate, blood glucose, and various hepatic parameters in spontaneously hypertensive rats

We examined the effects of Ginkgo biloba extract (GBE) feeding on blood pressure, heart rate, blood glucose, and various hepatic parameters in spontaneously hypertensive rats (SHR). Male SHR (10 weeks old) were fed either a control diet or diet containing GBE (0.5% and 2% w/w) for 36 days. Average intakes of GBE in the 0.5% and 2% GBE diet groups were about 0.3 g/kg body weight/day and 1.3 g/kg body weight/day, respectively. The blood pressure and heart rate were continuously measured by a telemetric method, and showed a clear circadian rhythm (high at night and low in daytime). The heart rate both at night and in daytime was lowered in the 2% GBE diet group within a few days. The feeding of the GBE diet did not influence the systolic or diastolic blood pressure, blood glucose, or plasma insulin. However, the feeding of GBE diet increased liver weight in a GBE dose-dependent manner, and enhanced phospholipids concentration in the liver. In addition, feeding of the GBE diet markedly increased the content of cytochrome P-450, and the activity of glutathione S-transferase in the liver. Plasma transaminase activity was unaltered by the feeding of GBE diet. These results suggest that feeding of GBE to SHR had no beneficial effect on the parameters examined, but also had no obvious toxicity, even at a high dose of GBE.