A method for studying the effect of vasoactive substances on glomerular filtration without affecting the central haemodynamics.

A method for microcatheterization of rat kidneys was developed. The catheter consists of 50-100 micron thick polyethylene tubes, and is inserted into the interlobular or arcuate arteries via a lumbar artery. The technique makes it possible to perfuse a small number of nephrons with very high doses of vaso active substances without affecting the nephrons in the vicinity or the central haemodynamics. By adding labelled inulin to the perfusate it is also possible to calculate the amount of drug reaching the nephron under study. It was shown that the catheterization and perfusion with Ringer solution per se have no effect on the nephron function. Perfusion with very high doses of acetylcholine was found to have a selective effect on the area perfused but caused no changes in central haemodynamics, or on nephrons in unperfused areas. It is concluded that the technique is suitable for use in studies concerning the handling of high doses of vasoactive substances by the nephron.