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Spontaneous calcium oscillatory patterns in mammotropes display non-random dynamics.
S L Shorte1, W J Faught, L S Frawley
1Laboratory of Molecular Dynamics, Department of Cell Biology & Anatomy, Medical University of South Carolina, Charleston, South Carolina, USA.
Cell Calcium
|October 6, 2000
Summary
Mammotropes exhibit distinct intracellular calcium patterns. These patterns transition in an ordered, non-random sequence, suggesting a structured code regulating cell functions like exocytosis and gene expression.
Area of Science:
- Cell Biology
- Physiology
Background:
- Primary rat mammotropes display four distinct patterns of spontaneous intracellular calcium ([Ca2+]i) oscillations: quiescent (A) and three oscillatory (B, C, D) states.
- Previous observations showed frequent interconversion between these [Ca2+]i phenotypes over time, raising questions about the nature of these transitions.
Purpose of the Study:
- To determine if the observed transitions between [Ca2+]i oscillatory phenotypes in mammotropes are random or ordered events.
- To investigate the duration of each phenotype episode and the probabilities of transitions between them.
Main Methods:
- Long-term, continuous measurements of intracellular calcium ([Ca2+]i) in primary rat mammotropes.
- Utilized Fura-2-dextran microinjection and a prolactin promoter-driven reporter plasmid for cell identification and calcium monitoring.
Main Results:
- Transitions between [Ca2+]i phenotypes occurred in approximately 25% of cells every 1-5 hours.
- Phenotype episodes exhibited varying durations (A: 1.04±0.2h, B: 1.64±0.3h, C: 2.45±0.62h, D: 0.90±0.2h).
- Specific transitions were more frequent, revealing an ordered pattern (C → B → A).
Conclusions:
- The transitions between intracellular calcium ([Ca2+]i) phenotypes in mammotropes are not random but follow a structured, ordered sequence.
- These ordered transitions support the hypothesis of a 'code' governing calcium-dependent regulation of cellular processes such as exocytosis and gene expression.