Renal Micropuncture Techniques

            This essay will critically review some of the major uses of renal micropuncture techniques, focusing in particular on the stationary method, free-flow micropuncture and renal microperfusion, the latter including both in vivo and in vitro methods. The essay will conclude with a short review of other uses of micropuncture. Wearn and Richards (1924) were the first people to use micropuncture successfully on the kidney. They successfully inserted a micropipette into the glomerulus of a single amphibian nephron and their results provided conclusive evidence that ultrafiltration of the blood occurred at this site. Walker, Bott, Oliver and MacDowell (1941) later extended the technique to the proximal and distal convoluted tubules. They demonstrated isosmotic reabsorption in the proximal convoluted tubule, and an above plasma concentration of chloride ions. This latter result implied that reabsorption in the kidney was not a simple passive affair. Gottschalk and Mylle (1958) micropunctured the loop of Henle providing conclusive evidence for Kuhn's theoretical countercurrent multiplier system, and Sakai, Jamison and Berliner (1965) micropunctured the collecting duct. A problem with micropuncture techniques is that they require exceptionally fine and skilled micromanipulation to avoid puncturing the other side of the tubule. This is why the original experiments, up until Gottschalk (1956), were done on amphibian nephrons. The problem with mammalian nephrons was that they were too small, had an absence of glomeruli on the surface of the kidney, and tended to move due to respiratory movements. These problems were overcome by a combination of two improvements. Alexander and Nastuk (1953) developed the micropipette puller, which mechanically "pulled" capillary tubes over heat, instead of by hand. This produced micropipettes with much smaller diameters (8x10-6m approx.) allowing more accurate micromanipulation.

Related Essays: