Calcium absorption pathway

"Calcium absorption pathways" is not a single molecule or receptor but rather refers to the physiological and molecular mechanisms by which calcium ions are absorbed from the intestinal lumen into the bloodstream. There are two main routes for intestinal calcium uptake: 1. Transcellular (active) pathway – Predominant in the duodenum and upper jejunum, this process involves several key proteins and steps[1][2][3][5][6]: - Entry of Ca²⁺ across the apical membrane via epithelial calcium channels such as TRPV6 (and to a lesser extent TRPV5). - Intracellular diffusion facilitated by cytosolic calcium-binding proteins like calbindin-D9k. - Extrusion across the basolateral membrane via plasma membrane Ca²⁺ ATPase (PMCA1b) and Na⁺/Ca²⁺ exchanger (NCX1). - This pathway is tightly regulated by vitamin D metabolites, especially calcitriol[2][4][5]. 2. Paracellular (passive) pathway – Occurs throughout the small intestine but is most significant when dietary calcium intake is high[1][2]. It involves passive movement of Ca²⁺ between enterocytes through tight junctions formed by claudins such as claudin 2 and claudin 12[4]. This route does not require energy or specific transporters. Both pathways are influenced by hormones including vitamin D, parathyroid hormone, calcitonin, estrogen, thyroid hormone, glucocorticoids; dietary factors like phytates or oxalates can inhibit absorption; physiological states such as growth or pregnancy can increase demand[2][6]. Because "calcium absorption pathways" describes a set of processes involving multiple molecules rather than a discrete therapeutic target like an enzyme or receptor protein, it should not be considered a canonical drug target. Instead, individual components—such as TRPV6 channel or calbindin-D9k—are valid molecular targets. If you need structured information on specific molecules within these pathways—for example "TRPV6", "calbindin-D9k", "plasma membrane Ca²⁺ ATPase"—please specify which one so that detailed data can be provided for that entity. The term “Calcium absorption pathways” refers to physiological processes involving multiple proteins responsible for intestinal uptake of dietary calcium via transcellular and paracellular mechanisms regulated primarily by vitamin D and other hormones; it does not denote a single molecule/receptor suitable for direct pharmacological targeting[1][2][3][4][5].

Other names

Intestinal calcium absorptionCalcium transport pathwaysIntestinal Ca2+ absorption