Contraction of guinea pig lung parenchyma by pancreatic type phospholipase A2 via its specific binding site.
Porcine pancreatic group I phospholipase A2 (PLA2-I) induced contraction of guinea pig parenchyma in a concentration-dependent manner. Its EC50 value was similar to the Kd value calculated from the specific binding of 125I-labeled porcine PLA2-I in the membrane fraction of guinea pig lung. Type-specific action of PLA2's and homologous desensitization strongly implicated the involvement of PLA2-I-specific sites in the activation process. Thromboxane A2 was found to be the main product from lung tissue by PLA2-I action and the contractile response by PLA2-I was specifically suppressed by thromboxane A2 receptor antagonists and cyclooxygenase inhibitor, but not by leukotriene receptor antagonist and H1 blocker. These findings indicate that PLA2-I-induced contractile response may depend on the secondarily produced thromboxane A2, thus providing a new aspect of PLA2-I from the pathophysiological standpoint.
Kanemasa
T
T
Shionogi Research Laboratories, Shionogi & Co., Osaka, Japan.
Arimura
A
A
Kishino
J
J
Ohtani
M
M
Arita
H
H
D000818:Animals; D001665:Binding Sites; D003286:Contracture / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism* / Q000502:physiology; D008297:Male; D010179:Pancreas / Q000201:enzymology*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D013928:Thromboxane A2 / Q000378:metabolism
D013928:Thromboxane A2; D010741:Phospholipases A; D054467:Phospholipases A2