Decreased [20-3H]phorbol-12,13-dibutyrate binding to phospholipase C pretreated epidermal cells

Incubation of mouse epidermal cells (HEL-37) with phospholipase C (Clostridium perfringens) caused about a 50% decrease in the specific binding of [20-3H]phorbol-12,13-dibutyrate. Phospholipase C caused a decrease in the apparent number of binding sites from 2.86 X 10(5) to 1.21 X 10(5) per cell with little effect on ligand affinity. The decrease was observed with purified phospholipase containing no detectable protease activity, and when cells were fixed with glutaraldehyde. The phorbol-12,13-dibutyrate binding capacity of treated cells was recovered within 4 h incubation in complete medium. The results suggest that not all phorbol ester binding sites are equivalent, with differences arising either from varying phospholipid requirements or from membrane localisation.