Ca absorption is mediated by both active and passive processes. Absorption in both proximal tubule and thick ascending limb is mainly coupled indirectly to Na absorption and is a passive process through the paracellular pathway. In the distal convoluted tubule, Ca absorption is regulated independently of Na absorption; this is the principal site of action of parathyroid hormone, calcitonin, and 1,25-(OH)2D3. Models for transport in proximal tubule, thick ascending limb, and distal convoluted tubule afford attractive explanations for the influence on Ca transport of effective arterial blood volume, parathyroid hormone, acid-base balance, genetic disturbances such as Bartter's and Gitelman's syndromes, and diuretic action.
ASJC Scopus subject areas
- Physiology (medical)