Effects of Arterially Infused Hydroalcoholic <i>Agaricus blazei</i>Extracts on Perfusion Pressure and Oxygen Uptake in the Bivascularly Perfused Rat Liver

In a preceding work we have reported experiments showing that an hydroalcoholic exctract of Agaricus blazei is able to exert purinergic effects in the isolated perfused rat liver when it is infused into the portal vein in monovascular perfusion (entry: portal vein;exit: hepatic vein). In the present communication we are presenting and discussing experiments done with the bivascularly perfused rat liver (entry: portal vein + hepatic artery;exit: hepatic vein) in order to verify if the hemodynamic effects also occur in the arterial bed. It was found that the A. blazei extract is also active when infused into the hepatic arterial bed, with differences in both sensitivity and nature of the effects on either perfusion pressure or oxygen consumption. Constriction of the arterial bed required much higher concentrations of the extract than the portal bed. The kinetics of the response was also different, with a biphasic instead of a monophasic response. These results provide a promising starting point for future studies aiming to bring to light more mechanistic details about these and possibly other effects.

The in Vitro Antioxidant Capacities of Hydroalcoholic Extracts from Roots and Leaves of Smallanthus sonchifolius (Yacon) Do Not Correlate with Their in Vivo Antioxidant Action in Diabetic Rats

Leaf and root extracts of Smallanthus sonchifolius (yacon), have antihyper-glycemic activity and antioxidant properties. The present study aims to compare the in vivo hepatic antioxidant activity of hydroalcoholic extracts of yacon leaves and roots in rats with streptozotocin-induced diabetes in terms of their in vitro antioxidant capacity. Rats were treated during 14 days with 1060 mg·Kg-1 root extract or 400 mg·Kg-1 leaf extract. The latter was richer in phenolics and possessed a much higher in vitro antioxidant activity. Both extracts prevented hyperglycemia in diabetic rats. The liver of diabetic rats presented increased levels of protein carbonyls and ROS and decreased activities of antioxidant enzymes. Treatment with both root and leaf extracts restored the protein carbonyl levels to normality. The root extract also restored the ROS levels to normality, but the leaf extract was not effective. The root extract was also more effective in restoring the activity of at least two important antioxidant enzymes (glucose 6-phosphate dehydrogenase and glutathione peroxidase). In terms of the antioxidant load (which was 17 times lower in the root extract treatment), the in vivo action of the root extract was more effective than the leaf extract in reducing the hepatic oxidative stress that accompanies diabetes.

The Action of p-Synephrine on Lipid Metabolism in the Perfused Rat Liver

p-synephrine and p-octopamine were found to increase lipolysis in adipocytes. The present study approaches the question if these compounds, natural products of the bitter orange (Citrus aurantium fruit), increase lipolysis and fatty acid oxidation in the liver. Experiments were done in the perfused rat liver. Non-recirculating hemoglobin-free perfusion was done using the Krebs/ Henseleit-bicarbonate buffer (pH 7.4) as perfusion fluid. Both p-synephrine and p-octopamine, at the concentrations of 100 μM, were found to stimulate the hepatic triacylglycerol lipase by 40% and 51%, respectively. These seem to be the maximal stimulations possible in the liver. In the perfused liver, p-synephrine, when present at an initial concentration of 500 μM, was able to increase the non-esterified fatty acid release after one hour of recirculating perfusion. The effects of p-synephrine on the oxidation of exogenously supplied [1-14C]octanoate and [1-14C]oleate were minimal. Only oxygen uptake, already stimulated by octanoate or oleate, was additionally increased by the infusion of p-synephrine. These results contrast with those obtained in a previous study with p-octopamine, which increased the production of 14CO2 from both [1-14C]octanoate and [1-14C]oleate. Apparently only the oxidation of endogenous fatty acids is stimulated by p-synephrine. On the other hand, both p-synephrine and p-octopamine stimulate the hepatic triacylglycerol lipase to a much lesser extent than the adipocyte lipase. It can be concluded that p-synephrine affects much more carbohydrate metabolism in the liver than lipid metabolism.