Objective    In order to understand the response of pulmonary artery smooth muscle cells (PASMCs) to hypoxia and explore the mechanism of hypoxic pulmonary vasocontriction (HPV)

the ch

anges of membrane potentials

cytoplasmic and mitochondrial Ca

2+

under hypoxic stimulation were investigated.     Methods    PASMCs from adult SD rats were isolated

cultured and identified. Hypoxic stimulation was made by adding Na

2

S

2

O

4

(2 mmol/L) to the incubation media. The fluorescent intensity of cell membrane potential

cytoplasmic and mitochondrial Ca

2+

was measured under confocal microscopy after PASMCs loaded with the fluorescent indicators Di-8-ANEPPS (2 μmol/L)

Fluo-4/AM (4 μmol/L) and Rhod-5F (5 μmol/L) respectively. Each sample was observed for 10 min.     Results    After Na

2

S

2

O

4

stimulation

the fluorescent intensity of PASMCs membrane potentials recovered following a transient significant decrease

increased gradually to the climax at 100 s and then decreased gradually to the level lower than the initial value. The fluorescent intensity of cytoplasmic Ca

2+

increased gradually. The fluorescent intensity of mitochondrial Ca

2+

increased transiently and lasted about 30 s but then decreased below the initial value

and followed by a steady increase above the initial value.     Conclusion    Under hypoxic stimulation

the membrane potential

cytoplasmic and mitochondrial Ca

2+

changed dynamically in specific patterns. In addition to disturbance of cytoplasmic Ca

2+

disturbance of mitochondrial Ca

2+

might play important roles in the development of HPV.