Mechanisms underlying impairment of endothelium-dependent relaxation by fetal bovine serum in organ-cultured rat mesenteric artery

Organ culture of blood vessels provides a useful technique to investigate long-term effects of drugs because tissue architecture and function are well preserved. Various growth factors are responsible for structural and functional changes during vascular diseases. We investigated long-term effects of fetal bovine serum (FBS) which contains such factors on endothelium-dependent relaxation using organ-culture method. Rat isolated mesenteric arteries with endothelium were cultured for 3 days without or with 10% FBS (FBS). Acetylcholine- and bradykinin-induced endothelium-dependent relaxations were significantly impaired in FBS, whereas sodium nitroprusside-induced relaxation of endothelium-removed artery was unchanged. Morphological examination revealed that endothelium was intact in FBS. Acetylcholine-induced nitric oxide (NO) release as detected by 4, 5-diaminofluorescein significantly decreased in FBS, whereas endothelial NO synthase expression was unchanged. A Ca 2+ ionophore, A23187-induced relaxation was unchanged in FBS. A phospholipase C activator, m-3M3FBS-induced relaxation of FBS was unchanged in either Ca 2+-containing or -free solution. Total expressions of transient receptor potential canonical channels (TRPCs: TRPC-1, -4, -5) were similar in FBS. These data suggest that FBS impairs endothelium-dependent relaxation by inhibiting events upstream of phospholipase C activation including phospholipase C, G-protein, and receptors in endothelium. [Display omitted]