Cholera toxin and dibutyryl cyclic-AMP stimulate the growth of epithelial cells derived from epithelial rests from porcine periodontal ligament

The epithelial cells (E-cells) grew best at high (greater than 5 per cent) concentrations of fetal bovine serum (FBS). Growth could be obtained at low concentrations of dialysed FBS (DFBS) if the medium (alpha-MEM) was modified so that the levels of Ca2+ and K+ were reduced to 0.1 and 1.0 mM, respectively (beta-MEM). The addition of 0.5 per cent DFBS to the beta-MEM did not initiate good growth but was sufficiently supportive to enable the effects of various growth promoters to be tested. Cholera toxin and dibutyryl cyclic-3'5'-adenosine monophosphate (Bt2cAMP), which are known to increase intracellular cAMP levels, at concentrations of 1 ng/ml and 0.5 mM, respectively increased cell number. Cholera toxin caused the E-cells to be more flattened when viewed by phase-contrast; this appeared to be due to spread of the cells. No difference in cell-size distributions obtained between the trypsinized E-cells grown in the presence or absence of cholera toxin was observed. Epithelial proliferation that occurs in dental cysts could result from a rise in intracellular cAMP levels in epithelial cell rests.