Related Experiment Videos
Extracellular nucleotides elevate [Ca2+]i in rat osteoblastic cells by interaction with two receptor subtypes
1Department of Physiology, Faculty of Dentistry, University of Western Ontario, London, Canada.
The American Journal of Physiology
|November 1, 1992
Summary
Extracellular nucleotides, like ATP, trigger calcium release in rat osteoblastic cells via two P2-purinoceptor subtypes. This calcium signaling pathway shows time-dependent inactivation with sustained receptor stimulation.
Area of Science:
- Cell Biology
- Molecular Pharmacology
- Biochemistry
Background:
- Extracellular nucleotides modulate cellular functions through specific cell-surface receptors.
- Elevation of cytosolic free Ca2+ concentration ([Ca2+]i) is a key response mediated by nucleotides in various cell types.
- Osteoblastic cells play a crucial role in bone metabolism and are potential targets for nucleotide signaling.
Purpose of the Study:
- To investigate the effects of extracellular nucleotides on intracellular calcium levels in the rat osteoblastic cell line UMR-106.
- To identify the specific nucleotide receptors involved and characterize their signaling pathways.
- To elucidate the mechanisms underlying nucleotide-induced calcium transients in osteoblasts.
Main Methods:
- Indo-1 fluorescence spectrophotometry was employed to measure intracellular calcium ([Ca2+]i) in UMR-106 cells.
- Cells were stimulated with various extracellular nucleotides, including ATP, UTP, ADP, and their analogs.
- Dose-response relationships and effects of sequential/simultaneous stimulation were analyzed.
Main Results:
- ATP induced a significant, rapid increase in [Ca2+]i, primarily through the release of calcium from internal stores.
- Specific nucleotides (ATP, UTP, ADP) elicited calcium transients, indicating receptor specificity, while others (adenosine, AMP) did not.
- Evidence suggests the presence of at least two distinct P2-purinoceptor subtypes mediating calcium mobilization, with differential ligand selectivity and a time-dependent inactivation of the signaling pathway.
Conclusions:
- Extracellular nucleotides elevate intracellular calcium in osteoblastic cells via interaction with two distinct P2-purinoceptor subtypes.
- These receptors are linked to calcium mobilization pathways, involving release from internal stores.
- The findings highlight the complexity of nucleotide signaling in osteoblasts and its potential role in bone cell function.