A novel method for infusing drugs continuously into the renal artery of rats

A method is described to achieve a homogeneous intravascular distribution of drugs infused into the renal artery of anesthetized rats. The device for intrarenal infusion consisted of a multiple-catheter system with a cannula inserted into the renal artery, which was connected to different lines for drug infusions and to one line for oscillating blood back and forth in the renal cannula with a magnetic membrane pump. The blood oscillation served to mix the drugs with renal arterial blood. To verify the usefulness of this procedure, Lissamine green was infused into the renal artery; without the mixing pump the dye was located on a small portion of the kidney surface, whereas the dye could be visualized evenly distributed and less concentrated over the entire kidney with the pump. With the mixing device, intrarenal infusion of angiotensin II, 5 pmol.kg-1.min-1, or norepinephrine, 150 pmol.kg-1.min-1, reduced renal blood flow by approximately 25% without affecting blood pressure. Tenfold higher doses given intravenously had comparable renal effects, but these increased systemic pressure. Without the mixing pump, vasoactive drugs given into the renal artery had a distinctly smaller effect on renal blood flow than with the pump (angiotensin II, 39%; norepinephrine, 49%; and acetylcholine, at 5 nmol.kg-1.min-1, 33%). The results show that intrarenally infused drugs, without a mixing device, have access to an unpredictably small kidney volume, and estimation of their effects on kidney functions can be equivocal. The present device ensures an adequate mixing of drugs with renal blood.