PMA activates the respiratory burst independently of p21rac. (A) Neutrophils were stimulated with fMLP (10⁻⁸mol/L), PMA (100 ng/mL), ionomycin (500 nmol/L), or thapsigargin (100 nmol/L) for the time indicated. p21rac activation was determined as described. (B) In cells from the same donor, oxygen consumption was measured after stimulation with PMA (100 ng/mL).