Histamine release from Weibel-Palade bodies of toad aortas induced by endothelin-1 and sarafotoxin-S6b

Endothelin-1 (ET-1) and sarafotoxin-S6b (STX) induce a remarkable degranulation of Weibel-Palade (WP) bodies prior to the vasocontraction of toad aortas. As WP bodies play the role of a reservoir site of the histamine in the endothelial cells, there is the possibility that ET-1 and STX evoke the release of histamine from WP bodies of this vessel.

Histamine concentrations were assayed by high-performance liquid chromatography (HPLC) from the perfusate after being perfused with a solution containing ET-1 and STX. Each vessel was fixed and embedded for conventional electron microscopy and immunoelectron microscopy using antihistamine sera.

The appreciable concentrations of histamine were assayed by HPLC from the perfusate after the toad aortas were perfused with a solution containing ET-1 and STX. The immunoelectron microscopy revealed that histamine immunoreactive gold particles in the WP bodies remarkably decreased in number in the treated samples when compared to the control ones. Our immunoelectron micrographs indicated that the release of histamine from the endothelial cells occurred in association with the degranulation and the exocytosis of the WP bodies after treatment with ET-1 and STX.

The present study clearly shows that ET-1 and STX induce the histamine release from WP bodies of the toad aortas by means of HPLC and immunoelectron microscopy. Histamine discharged from the WP bodies may be involved in the vasocontraction evoked by ET-1 and STX.