Behavior of embryonic chick heart cells in culture. 2. Cellular responses to epidermal growth factor and other growth signals.
Muscle cell-enriched primary cell cultures were prepared from 8-day embryonic chick heart ventricles (74% of these cells showed positive staining with anti-cardiac myosin antibody). To determine if Epidermal Growth Factor ( EGF) affects cardiac muscle cells, immunostaining and autoradiography were performed to find the Muscle Cell Labeling Index (MLI). MLI represents the proportion of cardiac myosin-positive cells that specifically incorporated [3H]thymidine. The MLI for EGF-treated cells was 51%. Controls in Serum-free Nutrient Medium (SFNM) had a MLI of 34.5%. Combinations of growth signals also were tested. EGF, IGF-I (Insulin-like Growth Factor-I), or PDGF (Platelet-derived Growth Factor) alone increased [3H]thymidine incorporation in the cells. Adding IGF-I or PDGF simultaneously with EGF enhanced the response of the cells to EGF by increasing [3H]thymidine incorporation. TGF-beta (Transforming Growth Factor-beta) alone was shown to have an inhibitory effect on [3H]thymidine incorporation, and when TGF-beta was added together with EGF, it attenuated the stimulatory effect of EGF on [3H]thymidine incorporation. Phorbol 12-Myristate 13-Acetate (PMA), a tumor promoter, alone had no effect on [3H]thymidine incorporation, but its addition suppressed the stimulatory effect of EGF when they were added simultaneously in the presence of 5% FBS. Developmental response of the heart cells to growth signals also was tested. Heart cells from 18-day embryos were used to test the effect of insulin and EGF. Although both insulin and EGF increased [3H]thymidine incorporation in heart cells from 8-day embryos, different responses to insulin and EGF occurred with heart cells from 18-day embryos. Whereas the heart cells from 18-day embryos still responded to EGF by increasing [3H]thymidine incorporation, they did not show a response to insulin as measured by [3H]thymidine incorporation, suggesting that the loss of response of the heart cells to growth signals may occur at the receptor level. Further studies show that EGF, TGF-alpha, aFGF, and PDGF increased the total numbers of heart cells, and that aFGF and PDGF also increased the percentages of heart muscle cells.[1]References
- Behavior of embryonic chick heart cells in culture. 2. Cellular responses to epidermal growth factor and other growth signals. Lau, C.L. Tissue & cell. (1993) [Pubmed]
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