Calcium Transport in the Pars Recta and the Loop of Henle

Abstract

In 1963 Lassiter et al¹ concluded from micropuncture studies that approximately 60% of the filtered calcium was reabsorbed in the proximal tubule and 35% was absorbed by more distal segments. Since only about 10% of the filtered calcium remains at the early distal convoluted tubule,² the loop of Henle must absorb about 30% of the filtered load. Comparing the findings at the hairpin bend of the loop of Henle in the hamster to those in the distal tubule of the rat, Lassiter et al¹ concluded that the thick ascending limb (TAL) was the major site of calcium absorption. Five different laboratories, including our own, have investigated calcium transport in this segment directly using the isolated rabbit renal tubule perfused in vitro by the method of Burg et al.³