ISSN:
1432-069X
Keywords:
Keratinocytes
;
Cell differentiation
;
Cell growth
;
Epidermal growth factor
;
Phorbol ester
;
Intracellular calcium
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The effect of growth and differentiation stimuli on intracellular free calcium ([Ca2+]i) in cultured human keratinocytes was investigated using micro-spectrofluori-metric techniques and the calcium-sensitive dye FURA-2. The mean [Ca2+]i of keratinocytes in 70 ΜM calcium medium was 104 ± 3 nM (mean ± SEM), significantly lower than the transformed keratinocyte line SVK14 (128 ± 2 nM). When cultured in 2.0 mM calcium medium the [Ca2+]i increased in both normal and transformed keratinocytes to 135 ± 4 nM and 180 ± 4 nM, respectively. Keratinocytes grew more slowly in the absence of EGF, but [Ca2+]i was unaltered. Stimulation with EGF (10 ng/ml) induced, over 4 min, a large transient rise in [Ca2+]i up to 230 nm, due to an influx of extracellular calcium. Heterogeneity of keratinocytes was observed with 46% (n=13) responding, but confluent or differentiated keratinocytes did not respond. TGF-Β (1 ng/ml) reduced cell growth without inducing differentiation and was not associated with any change in [Ca2+]i. The phorbol ester TPA (50 nM) induced irreversible growth arrest and terminal differentiation and increased the [Ca2+]i from 102 ± 2 nM to 126 ± 3 nM at 2 h, an effect similar to that of 2 mM extracellular calcium. Addition of 500 nM TPA was associated with a rise in [Ca2+]i, over several minutes to a plateau of 200–300 nM, due to release from internal stores and an influx of extracellular calcium. In normal human keratinocytes an increase in [Ca2+]i appears to be an early event in differentiation, whether induced by calcium or TPA, but not during growth inhibition without differentiation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00373354
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