Separation of different receptor-mediated effects of a prostaglandin H2 analogue (U46619) on human platelets by means of human granulocytic elastase and chymotrypsin.

Previous investigations indicated two classes of thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors on human platelets and suggested that shape change and myosin light chain phosphorylation correlated with the occupancy of high affinity receptors while serotonin release was related to a putative low affinity binding component (Morinelli TA et al., Am J Physiol 253: H1035-H1043, 1987). The current study shows that chymotrypsin destroyed three receptor-mediated responses of platelets to U46619 (a TXA2/PGH2 agonist), i.e. shape change, myosin light chain phosphorylation and serotonin release. Human granulocyte elastase selectively inactivated platelet ability to release serotonin following stimulation with U46619, but it did not affect significantly shape change and myosin light chain phosphorylation. In conclusion, it is possible to separate different receptor-mediated effects of U46619 on human platelets by means of human granulocytic elastase and chymotrypsin.