Summary
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% inhibition is obtained with 20 ¼M CTC after 1 hr incubation. 50 ¼M CTC causes
much greater inhibition, especially after short time incubation. The level of metabolic
ATP is decreased about 60% with both 20 and 50 ¼M 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.
Key words
Chlortetracycline - Calcium antagonists - Platelet inhibitor - Platelet metabolism
- Tetracycline analogs - Platelet leakage
