An Improved Method for Injection of Bolus Doses of Drugs into the Perfusion Circuit of Isolated Perfused Rat Kidney Utilizing a Six-port Injection Valve

The isolated perfused rat kidney experiment was introduced in 1959 for studying the regulation of renal blood flow and is recognized as a valuable preparation for studying physiological and biochemical as-pects of renal function such as hemodynamics, glomerular filtration rate (GFR) and overall handling of fluids. Dose-response curves are obtained by injection of bolus doses of drugs into the perfusion line. However current injection methods can cause several problems such as low reproducibility and altered baseline pressure. The aim of the present work is to develop a simple method of introducing the drug into the perfusion circuit which is free from these aberrations. This was achieved using a six-way injection valve placed in the perfusion circuit, just before the kidney. To assess the reproducibility of this method, 400 μL epinephrine (10-7 M) was injected seven times into an isolated perfused rat kidney. The mean peak pressure rise (mmHg) was 30.3±0.6, 28.5±0.8 and 27.1±0.6 at 100, 120 and 140 mmHg base per-fusion pressures respectively. Base pressure returned to pre-injection levels under all conditions tested. Low standard deviation of pressure maxima indicates the high reproducibility of this method while multiple injections can be made in a relatively shorter time. This method can be applied to all organ perfusion set-ups such as isolated hind limb, tail, arteries and arterioles.