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Fetal rabbit pulmonary artery smooth muscle cell response to ryanodine is developmentally regulated
V A Porter1, H L Reeve, D N Cornfield
1Division of Pediatric Pulmonology and Critical Care Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA. porte030@tc.umn.edu
Insights
Intracellular calcium handling in pulmonary artery smooth muscle cells (PASMCs) differs developmentally. Fetal distal PASMCs uniquely use ryanodine-sensitive calcium release and K(Ca) channels together to control calcium.
Area of Science:
- Physiology
- Cell Biology
- Developmental Biology
Background:
- Intracellular calcium regulation is crucial for smooth muscle function.
- Pulmonary artery smooth muscle cells (PASMCs) play a key role in regulating pulmonary blood flow.
- Developmental changes in calcium handling may impact pulmonary vascular function.
Purpose of the Study:
- To investigate developmental alterations in intracellular calcium handling within rabbit pulmonary artery smooth muscle cells (PASMCs).
- To elucidate the specific mechanisms controlling calcium in PASMCs across different developmental stages.
Main Methods:
- Isolation of PASMCs from rabbit pulmonary arteries at fetal, newborn, and juvenile stages.
- Utilized calcium-sensitive dye fura 2 to measure intracellular calcium.
- Employed electrophysiology and confocal microscopy to assess cellular function.
Main Results:
- All age groups showed calcium release with caffeine.
- Ryanodine increased calcium only in fetal distal PASMCs, dependent on extracellular calcium influx.
- Iberiotoxin and ryanodine interacted, suggesting a coupled mechanism in fetal distal PASMCs.
- Fetal distal PASMCs exhibited spontaneous transient outward currents and calcium sparks.
Conclusions:
- Ryanodine-sensitive calcium release from the sarcoplasmic reticulum and calcium-sensitive potassium (K(Ca)) channels interact to regulate intracellular calcium.
- This coordinated calcium control mechanism is specific to fetal distal PASMCs.
- These findings highlight a unique developmental regulation of calcium handling in the pulmonary vasculature.
Abstract:
To study developmental changes in intracellular calcium handling in pulmonary artery smooth muscle cells (PASMCs), cells were isolated from distal and proximal pulmonary arteries from rabbits at different developmental stages: juvenile (4-6 wk old), newborn (<48 h), and full-term fetal. Isolated PASMCs were studied using the calcium-sensitive dye fura 2. Cells from each age group responded to caffeine with an increase in calcium; however, ryanodine (50 microM) only increased calcium in fetal distal PASMCs. The ryanodine-induced increase was due to influx of extracellular calcium because it was blocked by removal of extracellular calcium or by diltiazem. The calcium-sensitive potassium (K(Ca)) channel blocker iberiotoxin produced a transient increase in calcium in the fetal distal PASMCs, which could be inhibited by prior application of ryanodine. Conversely, the ryanodine response was inhibited if iberiotoxin was given first. With the use of electrophysiology and confocal microscopy, fetal PASMCs were shown to exhibit spontaneous transient outward currents and calcium sparks, respectively. These observations suggest that ryanodine-sensitive release of calcium from the sarcoplasmic reticulum and K(Ca) channels act together to control intracellular calcium only in fetal distal PASMCs.