The renal connecting tubule: Resolved and unresolved issues in Ca(2+) transport.
The renal connecting tubule (CNT) localizes to the distal part of the nephron between the distal convoluted tubule and the collecting duct, and consists of two different cell types: segment-specific and intercalated cells. The former reabsorb water (H(2)O), sodium (Na(+)) and calcium (Ca(2+)) ions to the blood compartment, while secreting potassium ions (K(+)) into the pro-urine. The latter cells contribute to the renal control of the acid-base balance. Several factors and hormones tightly regulate these transport processes. Although the CNT reabsorbs only ∼15% of filtered Ca(2+) load, this segment is finally decisive for the amount of Ca(2+) that appears in the urine. Impaired Ca(2+) transport across CNT can provoke severe urinary Ca(2+) excretion, called hypercalciuria. This review mainly focuses on the activity, abundance and expression of the epithelial Ca(2+) channel named Transient Receptor Potential Vanilloid 5 (TRPV5) that is the gatekeeper of active Ca(2+) reabsorption in the CNT.
Markadieu
Nicolas
N
Department of Physiology, Radboud University Nijmegen Medical Centre, The Netherlands.
Bindels
René J
RJ
Hoenderop
Joost G
JG
D000136:Acid-Base Equilibrium / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004847:Epithelial Cells / Q000473:pathology / Q000502:physiology*; D005260:Female; D006728:Hormones / Q000378:metabolism; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D007668:Kidney / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology*; D008297:Male; D051379:Mice; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism; D014867:Water / Q000378:metabolism
D006728:Hormones; D050916:TRPV Cation Channels; D014867:Water; D012964:Sodium; D011188:Potassium; D002118:Calcium