Osmoregulation in the renal papilla: membranes, messengers and molecules.
This contribution summarizes recent progress in the understanding of the molecular basis of the release of organic osmolytes that occurs when inner medullary cells are confronted with a drop in osmolarity in their environment. For sorbitol release across the basolateral membrane an increase in intracellular calcium seems to be the prominent signal, initiated by G-protein activation, followed by phosphatidylcholine phospholipase activation and generation of arachidonic acid. The increase in betaine permeability is also G-protein dependent but calcium independent, and is restricted to the basal-lateral cell face. Myo-inositol and glycerophosphorylcholine efflux are calcium and G-protein independent and occur both across the apical and basolateral membrane, although to a different extent. Taurine release is also calcium and G-protein independent; a swelling-activated anion channel at the basolateral membrane represents the major efflux pathway.
Kinne
R K
RK
Max-Planck-Institut für molekulare Physiologie, Abteilung Epithelphysiologie, Dortmund, Germany.
Boese
S H
SH
Kinne-Saffran
E
E
Ruhfus
B
B
Tinel
H
H
Wehner
F
F
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D007679:Kidney Medulla / Q000737:chemistry / Q000502:physiology*; D015290:Second Messenger Systems / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000502:physiology*