Species difference in increased vascular permeability by synthetic leukotriene C4 and D4

The activity of synthetic LTC4 was tested in guinea-pig ileum and was 200 times more potent than histamine in contraction of the ileum (3 x 10(-11) M- 3 x 10(-9) M). The activities of LTC4 and LTD4 in increased vascular permeability in guinea pigs, rats and rabbits were compared with those of histamine, bradykinin and prostaglandin (PG) E2. LTC4 was approximately equipotent to bradykinin on a molar basis in guinea pigs and rats and 5-100 times more potent than histamine. LTD4 was about 10 times more potent than LTC4 in guinea pigs and was equipotent to LTC4 in rats. On the contrary, in rabbits, neither LTC4 (up to 30 nmole/site) nor LTD4 (1 nmole/site) induced the dye exudation. These results show that species difference is present in activity of LTC4 and LTD4 in vascular permeability. Furthermore, in guinea pigs, the vascular permeability increased by LTC4 was not affected after pretreatment with pyrilamine (2.5 mg/kg, i.v.), and LTC4 and LTD4 did not potentiate the activity of bradykinin in vascular permeability.