Figure 2.

Bioassay of endothelium-derived contracting factor in SHR aortic rings: layered or ‘sandwich’ preparation. Acetylcholine (ACh) produces contraction of the bioassay strip (without endothelium) only if endothelial cells are present on the donor aortic strip. L-nitro-arginine (L-NA) and tetrahydrobiopterin (BH₄) are present to optimize endothelium-derived contracting factor-mediated responses. Papaverine (Papav.) produces complete relaxation of the bioassay strip. Modified from Vanhoutte et al.(Br J Pharmacol, 2005).