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Expression of glucagon sensitivity by transformed MDCK cells normally unresponsive to glucagon: early commitment to
Abstract:
A cloned line of canine kidney cells (MDCK) transformed with Harvey murine sarcoma virus, in contrast to the parental, untransformed line, expressed glucagon sensitivity only under controlled culture conditions. The glucagon sensitivity of transformed MDCK cells appeared after 10 days of culture if plated at less than 100,000 cells/dish or after 3 days if cells were plated at greater than 300,000 cells/dish. As there was no effect of conditioned medium from glucagon-sensitive cells on insensitive cells, media components seemed not to be involved in this phenomenon. Glucagon sensitivity appeared more readily in defined as opposed to serum-containing medium. In fact, as little as 2% fetal bovine serum inhibited the expression of glucagon sensitivity when included in defined medium over the course of the experiment. Furthermore, when transformed MDCK cells were exposed to serum for only the first 24 hr of culture, glucagon sensitivity on day 11 was identical to that of cells exposed to serum throughout the entire experiment. In contrast, exposure to serum later in culture (days 4-8) had no inhibitory effect on the expression of glucagon sensitivity on day 11. The data suggest that differentiation, or glucagon sensitivity, occurs when transformed, glucagon-insensitive cells achieve a critical high density and that differentiation is sensitive to inhibition by serum only during the first 24 hr of culture.
Insights
Transformed canine kidney cells gain glucagon sensitivity at high densities. This differentiation is inhibited by early serum exposure, suggesting density and timing are key factors.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- MDCK cells are a canine kidney cell line used in various biological studies.
- Harvey murine sarcoma virus transformation can alter cellular properties.
- Glucagon sensitivity is a key indicator of differentiated kidney cell function.
Purpose of the Study:
- To investigate the conditions under which transformed MDCK cells acquire glucagon sensitivity.
- To determine the role of cell density and culture medium composition in this phenomenon.
- To elucidate the effect of serum exposure timing on the development of glucagon sensitivity.
Main Methods:
- Culturing transformed MDCK cells at varying initial cell densities.
- Assessing glucagon sensitivity under different culture conditions (defined vs. serum-containing medium).
- Evaluating the impact of early versus late serum exposure on glucagon sensitivity development.
Main Results:
- Transformed MDCK cells exhibited glucagon sensitivity only under specific culture conditions.
- Sensitivity expression was dependent on cell density, appearing faster at higher densities.
- Serum, particularly fetal bovine serum, inhibited glucagon sensitivity, with early exposure being most detrimental.
Conclusions:
- Cellular differentiation, indicated by glucagon sensitivity, in transformed MDCK cells is density-dependent.
- The acquisition of glucagon sensitivity is sensitive to serum inhibition primarily during the initial 24 hours of culture.
- These findings highlight the critical interplay between cell density, culture environment, and serum exposure in regulating cellular differentiation.