Anthocyanins are among the most common flavonoids in the human diet. In spite of their very low bioavailability, anthocyanins are indicated as active in preventing the progress of cardiovascular and neurodegenerative diseases, obesity, inflammation, and cancer. Any piece of knowledge concerning absorption, tissue distribution, metabolism, and excretion of dietary anthocyanins is expected to help understanding the apparent paradox between their low concentrations in cells and their bioactivity. The aim of this work was to investigate the renal uptake of dietary anthocyanins and the underlying molecular mechanism. A solution containing anthocyanins extracted from grape (Vitis vinifera) was introduced into the isolated stomach of anesthetized rats; after both 10 and 30 min, plasma, liver, and kidney were analyzed for their anthocyanin contents. While anthocyanins in the liver were at apparent equilibrium with plasma both after 10 and 30 min, kidney anthocyanins were 3- and 2.3-fold higher than in plasma, after 10 and 30 min, respectively. Since the transport activity of the bilitranslocase in kidney basolateral membrane vesicles was competitively inhibited by malvidin 3-glucoside (K(i) = 4.8 +/- 0.2 microM), the anthocyanin uptake from blood into kidney tubular cells is likely to be mediated by the kidney isoform of this organic anion membrane transporter.
