Intestinal calcium transport machinery

The intestinal calcium transport machinery is a coordinated physiological system responsible for the absorption of dietary calcium, primarily occurring in the duodenum and jejunum [1]. It comprises two distinct pathways: a passive paracellular route and an active transcellular route that is tightly regulated by the Vitamin D endocrine system [2]. The active transport process involves three main steps: apical entry via the Transient Receptor Potential Vanilloid 6 (TRPV6) channel, intracellular translocation facilitated by Calbindin-D9k, and basolateral extrusion into the blood by the Plasma Membrane Calcium ATPase 1 (PMCA1) [3]. This machinery is essential for maintaining systemic calcium homeostasis and bone mineralization; its dysfunction is a hallmark of metabolic bone diseases such as rickets and osteoporosis [4]. Therapeutic targeting of this system typically involves Vitamin D analogs that activate the Vitamin D Receptor (VDR) to increase the expression of these transport proteins, though such interventions require careful monitoring to avoid hypercalcemia and renal complications [1][4]. Citations: [1] Christakos S, et al. (2011) Mol Cell Endocrinol 347(1-2):25-29; [2] Fleet JC. (2017) Mol Cell Endocrinol 453:36-45; [3] Hoenderop JG, et al. (2005) Physiol Rev 85(1):373-422; [4] Bronner F. (2003) J Cell Biochem 88(2):387-393.

Other names

Transcellular calcium transport pathwayVitamin D-dependent calcium transport systemIntestinal calcium absorption system

Vitamin D receptor (VDR) agonists bind to the VDR, which then forms a heterodimer with the Retinoid X Receptor (RXR). This complex binds to Vitamin D Response Elements (VDREs) in the promoter regions of genes encoding the machinery's components, such as TRPV6 (apical entry), Calbindin-D9k (intracellular transport), and PMCA1 (basolateral exit), thereby increasing the rate of active calcium absorption [1][2][3].