Na(+)-Ca++ exchange mechanism in smooth muscle of the ureter.
The participation of Na+ in regulation of intracellular Ca++ content and in formation of spontaneous action potentials of guinea-pig ureter was studied. It was shown that the fast decrease of intracellular Ca++ in the Ca(++)-loaded muscles was accompanied by enhancement of Na+ content in the cells. The concentration gradient of Na+ was found to define the effectiveness of Ca(++)-extrusion from Ca(++)-loaded cells. The decrease of intracellular Ca++ showed a sigmoidal dependence on Na+ content in the medium. A correlation was established between the concentration gradient of Na+ and the formation of action potential plateau of ureter smooth muscle cells. The duration of action potential plateau decreased in accordance with Ca++ efflux and Na+ influx. The results confirmed the participation of Na(+)-Ca++ exchange mechanism in support of Ca++ cellular homeostasis as well as in the generation of action potentials of guinea-pig ureter.
Kazarian
K V
KV
L. A. Orbeli Institute of Physiology, Academy of Sciences of Armenia, Yerevan.
Hovhannissian
H S
HS
Hakobian
R R
RR
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D006168:Guinea Pigs; D006706:Homeostasis; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D017136:Ion Transport; D009130:Muscle, Smooth / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014513:Ureter / Q000378:metabolism*
D012964:Sodium; D002118:Calcium