The inhibitory effect of serum on cell attachment can be prevented by cobalt-protoporphyrin IX.

The rate of attachment of chick embryo fibroblasts (CEF) incubated for 1 h at pH 6 in the absence of serum, was equal to about 90% with 2% of spreading cells. The addition of 1% horse serum (HS) decreased to about 30% the rate of attached cells but increased to about 30% the proportion of spreading cells. We found that 3 microM cobalt-protoporphyrin IX (CoPP) added for 3 min before the addition of 1% HS increased both the rate of cell attachment (about 60%) and the proportion of cell spreading (about 50%).