Platelet aggregating activity of lysophosphatidic acids is not related to their calcium ionophore properties.
The calcium ionophore properties of A23187 and of two lysophosphatidic acid (LPA) analogs (1-palmitoyl- and 1-hexadecyl-sn-glycero-3-phosphate or P-GPA and H-GPA, respectively) were compared using platelet membrane vesicles loaded with 45Ca. Half maximal effect (HME) was obtained at 5 microM and 10 microM for H-GPA and P-GPA, respectively, against 0.7 microM for A23187, which released 2 times more Ca. The three compounds also induced platelet aggregation with a HME at 0.5 microM, 0.3 microM and 0.01 microM for A23187, P-GPA and H-GPA, respectively. The clear dissociation between the two effects appearing for both LPA raises some doubt about the general idea that (lyso) PA participate in cell activation through their calcium ionophore properties.
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D006801:Humans; D007476:Ionophores / Q000494:pharmacology*; D008246:Lysophospholipids; D010712:Phosphatidic Acids / Q000494:pharmacology*; D010743:Phospholipids / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*
D007476:Ionophores; D008246:Lysophospholipids; D010712:Phosphatidic Acids; D010743:Phospholipids; D000001:Calcimycin; D002118:Calcium