Key Points
- To determine the intracellular pathways through which angiotensin II and vasopressin mobilize calcium and stimulate phosphoinositide metabolism in vascular smooth muscle.
- Cultured vascular smooth muscle cells isolated from rat mesenteric arteries and loaded with the fluorescent indicator Fura-2.
- Evaluated cytosolic free calcium dynamics during hormone exposure both with and without extracellular calcium or depolarizing potassium.
- Quantified inositol phosphate isomers across time using high-pressure liquid chromatography and visualized subcellular calcium distribution with laser-excitation fluorescence.
- Both angiotensin II and vasopressin triggered transient, dose-dependent increases in cytosolic free calcium independent of extracellular calcium or voltage-dependent calcium channels.
- Vasopressin induced rapid, transient spikes in inositol 1,3,4-trisphosphate, inositol 1,4,5-trisphosphate, and inositol 1,3,4,5-tetrakisphosphate within one minute.
- Laser-excitation fluorescence imaging localized regions of high calcium concentration primarily within the subsarcolemmal compartment.
Structured PICO
PPopulationCultured vascular smooth muscle (VSM) cells from mesenteric artery of male Sprague-Dawley rats weighing 200-400 g
IInterventionAngiotensin II (AII) and Arg8-vasopressin (AVP)
CComparatorUnstimulated cells (basal condition) and high potassium depolarization
OOutcomeCytosolic free calcium concentration ([Ca2+]i) and inositol phosphate formationsurrogate
The study demonstrates that vasoconstrictive hormones angiotensin II and vasopressin mobilize intracellular calcium in vascular smooth muscle cells via receptor-mediated phosphoinositide hydrolysis rather than voltage-dependent calcium influx.