Antibodies against phospholipase C inhibit smooth muscle contraction induced by acetylcholine and histamine

The rationale of this study was to obtain a highly specific inhibitor of phospholipase C by raising rabbit antibodies against the purified bacterial phospholipase C. The antibodies inhibited the enzyme activity in vitro and, as shown by immunofluorescence, cross-reacted with the membrane-bound phospholipase C of isolated guinea-pig smooth muscle cells. Incubation (0–4 h) of guinea-pig taenia coli and ileum with antibodies resulted in a progressive inhibition (up to 85%) of the contractile response evoked by 2 μM acetylcholine or 2 μM histamine but did not inhibit significantly the contraction produced by prostaglandin F2α (0.1 μM). These inhibitory antibodies presumably represent the ‘missing tool’ needed to establish unequivocally if a given agonist acts via stimulation of the membrane-bound phospholipase C, and implicity phosphoinositide hydrolysis