Elucidation of kidney function by micropuncture: an historical perspective.

An understanding of the fundamental mechanisms of kidney function awaited the advent of micropuncture techniques. The initial micropuncture study by Wearn and Richards in 1924 presented the first direct evidence that the initial step in urine formation was the process of ultrafiltration at the glomerulus and that certain solutes were reabsorbed in the renal tubules. Subsequent micropuncture studies and the development by Burg and colleagues for in vitro perfusion of surviving tubular segments have provided an enormous amount of information about glomerular function and the transport characteristics of all nephron segments in the normal and diseased kidney.