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 microM acetylcholine or 2 microM histamine but did not inhibit significantly the contraction produced by prostaglandin F2 alpha (0.1 microM). 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 implicitly phosphoinositide hydrolysis.