WE investigated the in vitro effect of different forms of acidosis (pH 7.0)
on the formation of anaphylatoxins C3a and C5a. Metabolic acidosis due to
addition of hydrochloric acid (10 mu mol/ml blood) or lactic acid (5.5 mu m
ol/ml) to heparin blood (N=12) caused significant activation of C3a and C5a
compared to control (both p=0.002). Respiratory acidosis activated C3a (p
= 0.007) and C5a (p = 0.003) compared to normocapnic controls. Making blood
samples with lactic acidosis hypocapnic resulted in a median pH of 7.37. I
n this respiratory compensated metabolic acidosis, C3a and C5a were not inc
reased. These experiments show that acidosis itself and not lactate trigger
for activation of complement components C3 and C5.