Inhibition of thrombin-induced secretion from platelets by chlortetracycline and its analogs.

Chlortetracycline (CTC) (1.0 mM) blocks platelet secretion after a few seconds preincubation. The amount needed for inhibition can be reduced relative to time of preincubation. 50 micro M CTC. Two tetracycline analogs, anhydrotetracycline and demeclocycline (DMC), have different solubility properties in nonionic medium, but inhibit secretion at the same concentration, with little effect on the metabolic ATP level. The results suggest that CTC and its analogs do not inhibit platelet function by acting as metabolic inhibitors. While CTC causes increased leakage of cytoplasmic content at the concentrations where secretion is blocked more than 90%, DMC doses not cause leakage even at much higher concentration, so that there seems to be no connection between the induction of leakage (i.e. the membrane-active properties) and the inhibitory effect of the drugs.