Effect of leucotrienes C4, D4, prostacyclin and thromboxane A2 on isolated human cerebral arteries.

The effects of leucotrienes C4 (LTC4), D4 (LTD4), Prostacyclin (PGI2) and Thromboxane A2 (TXA2) were studied on superfused human cerebral artery strips. LTC4 and LTD4 neither contracted nor relaxed the strips. PGI2 caused a dose-dependent relaxation from 0.2 nmol to 0.8 nmol. When given simultaneously with a vasoconstrictor substance, PGI2 had an almost complete inhibitory effect. TXA2 caused a dose-dependent contraction from 0.03 nmol to 0.15 nmol. Also, TXA2 was more potent than 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2) with a contraction threshold of about 0.1 nmol. Prostaglandin E1 (PGE1), H2 (PGH2), and F2a (PGF2a) had contraction thresholds of about 1 nmol. Only a stable endoperoxide analogue (EPA), was more potent than TXA2, with a contraction threshold of 0.005 nmol. The possible role of these substances in producing ischaemic manifestations after subarachnoidal haemorrhage (SAH) is discussed.