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Uptake of sorbitol by chick embryo heart cells at various stages of development
Insights
Sorbitol uptake in chick embryo heart cells slows with development, primarily due to changes in transport kinetics. This suggests a carrier-mediated, but not active, transport system for sorbitol.
Area of Science:
- Cellular biology
- Developmental biology
- Biochemistry
Background:
- Sorbitol is a sugar alcohol found in various biological systems.
- Understanding nutrient transport is crucial for developmental studies.
Purpose of the Study:
- To investigate the mechanism and developmental changes in sorbitol transport into chick embryo heart cells.
Main Methods:
- Kinetics analysis of sorbitol uptake over developmental stages.
- Testing for active transport using inhibitors and gradient studies.
- Investigating potential interaction with the glucose transport system.
Main Results:
- Sorbitol entry into chick embryo heart cells begins at day five and decreases with further development.
- Uptake exhibits saturation kinetics, indicating carrier-mediated transport.
- Transport is not active (no concentration against gradient) and unaffected by metabolic inhibitors.
- Sorbitol uptake is independent of the glucose transport system, unaffected by insulin, glucose, or phloretin.
Conclusions:
- Sorbitol transport in chick embryo heart cells is carrier-mediated but not active.
- The decrease in uptake rate with development is attributed to an increase in apparent Km, not Vmax.
- Sorbitol utilizes a distinct transport pathway separate from glucose.
Abstract:
Sorbitol enters chick embryo heart cells from five days of development on. The rate of sorbitol entry becomes slower as development proceeds and the data suggest this is principally due to an increase in the apparent Km of transport, the Vmax remaining relatively constant. The uptake of sorbitol displays saturation kinetics and is believed on this ground to be carrier-mediated. Sorbitol does not appear to be actively transported since it is not concentrated against a gradient and its uptake is not inhibited by iodoacetate or 2, 4-dinitrophenol. Sorbitol does not appear to be taken up via the glucose transport system since uptake is not stimulated by insulin or inhibited by glucose or phloretin.