Spreading of human endothelial cells on fibronectin or vitronectin triggers elevation of intracellular free calcium.
Intracellular calcium ([Ca2+]i) was measured in FURA 2-loaded endothelial cells plated on fibronectin or vitronectin. Average values for [Ca2+]i increased to approximately twofold above basal levels by approximately 1 h after plating, and then declined. The increase in [Ca2+]i required extracellular calcium. Substituting potassium for sodium in the medium reduced the elevation of [Ca2+]i, a result that rules out the involvement of Na-Ca exchangers or voltage-dependent calcium channels, but that is consistent with the involvement of voltage-independent calcium channels. Plating cells on an anti-integrin beta 1 subunit antibody gave a similar [Ca2+]i response, but clustering beta 1 integrins with the same antibody, or occupying integrins with RGD (arg-gly-asp) peptides had no effect. Time course measurements on single cells revealed that in each cell [Ca2+]i rose abruptly at some point during spreading, from the basal level to a higher steady-state level that was maintained for some time. The elevated [Ca2+]i was unrelated to previously observed changes in intracellular pH, because chelating the Ca2+ in the medium failed to inhibit the elevation of pHi that occurred during cell spreading. In conclusion, these results show that integrin-mediated cell spreading can regulate [Ca2+]i, and the pathways involved are distinct from those that regulate intracellular pH.
Schwartz
M A
MA
Scripps Research Institute Committee on Vascular Biology, La Jolla, California 92037.
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology*; D005353:Fibronectins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D016023:Integrins / Q000502:physiology; D011940:Receptor Aggregation; D019096:Vitronectin
D015220:Calcium Channels; D005353:Fibronectins; D006023:Glycoproteins; D016023:Integrins; D019096:Vitronectin; D002118:Calcium