Tetrandrine and transmembrane signal transduction: effect on phosphoinositide metabolism, calcium flux and protein kinase C translocation in human lymphocytes.

Time-course and dose-dependent studies showed consistent suppression of phosphoinositide turnover in Con A-stimulated human lymphocytes in the presence of the plant alkaloid, tetrandrine. Significant inhibition of Con A-stimulated calcium flux was also observed. Furthermore, protein kinase C activity was also significantly inhibited by tetrandrine irrespective of whether Con A or phorbol myristate acetate was the stimulant. These results suggest that the immunosuppressive properties of tetrandrine are in part mediated by the capacity of tetrandrine to interfere with transmembrane signalling.