1 The aim of the present study was to characterize the subtypes of bradykinin (BK) receptors that evoke the relaxation and contraction induced by BK and to identify the main contracting and relaxing factors in isolated porcine basilar artery by measuring changes in isometric tension and a thromboxane (TX) metabolite. 2 Endothelial denudation completely abolished both responses. [Thi 5,8 , ]-BK (a B 2 -receptor antagonist) inhibited the BK-induced relaxation and contraction, whereas des-Arg 9 , [Leu 8 ]-BK (a B 1 -receptor antagonist) had no e ect. 3 L-nitro-arginine (L-NA, a nitric oxide synthase inhibitor) completely inhibited BK-induced relaxation. Indomethacin (a cyclo-oxygenase inhibitor) completely and ONO-3708 (a TXA 2 / prostaglandin H 2 receptor antagonist) partially inhibited BK-induced contraction, whereas OKY-046 (a TXA 2 synthase inhibitor) and nordihydroguaiaretic acid (a lipoxygenase inhibitor) did not. 4 In the presence of L-NA, the contractile response to BK was inhibited by indomethacin or ONO-3708 and was competitively antagonized by [Thi 5,8 , D-Phe 7 ]-BK (pA 2 =7.50). In the presence of indomethacin, the relaxant response to BK was inhibited by L-NA and was competitively antagonized by [Thi 5,8 , ]-BK (pA 2 =7.59). 5 TXA 2 release was not induced by BK-stimulation. 6 These results suggest that the endothelium-dependent relaxation and contraction to BK in the porcine basilar artery is mediated via activation of endothelial B 2 -receptors. The main relaxing factor may be NO and the main contracting factor may be prostaglandin H 2 .

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The measured reactivity indices (β-values) of heterocoerdianthrones (HCDs) in self-sensitized photoperoxidation indicate a high reactivity toward singlet-oxygen. Such a high reactivity is not only due to an effective singlet-oxygen production due to the highly fluorescent character, but also due to a strained structure, as predicted by a molecular calculation. On the other hand, the large thermal stability of their endoperoxides (POs), revealed by the large activation energy in thermal decomposition, is also explained by considering the strained structure of the parent HCDs. As a prospect of solar synthesis, one of the HCD derivatives was applied to a photosensitizer for singlet-oxygen oxidation.

In a radioligand binding study using bovine coronary artery endothelial cell membranes, captopril changed a single bradykinin (BK) binding site (Kd = 1.77 nM, Bmax = 60.2 fmol/mg protein) to high- (Kd = 0.68 pM, Bmax = 17.7 fmol/mg protein) and low- (Kd = 1.00 nM, Bmax = 72.5 fmol/mg protein) affinity binding sites. This effect was reversed by GppNHp. Captopril also enhanced BK-induced endothelium-dependent relaxation in saponin-treated coronary rings, and GppNHp partially suppressed this enhancement. These results suggest that captopril may affect BK receptors that couple to G-proteins.