Isolated Rat Aorta Contractile Studies

Vasorelaxation of the thoracic aorta was measured as described previously.¹³ In details, endothelium-denuded rings of rat thoracic aortae (2.0-mm wide) were suspended at a resting tension of 1.0 mN in a 15-mL organ bath (Isolated Organ Isometric Force 7003 Transducer; Ugo Basile, Gemonio, Italy) at 37°C in a solution containing in mmol/L of NaCl 130, KCl 4.0, CaCl₂ 1.8, MgCl₂ 1.0, NaH₂PO₄ 0.4, NaHCO₃ 19, and glucose 5.4 and gassed with a mixture of 95% O₂ and 5% CO₂ (pH 7.45); isometric contractions were recorded. The aortic rings were constricted twice with 80 mmol/L KCl, and after the washout, we studied the effect of increasing concentrations of a nitric oxide donor SNP (1 nmol/L−10 μmol/L) following constriction of vascular rings with 100 nmol/L endothelin-1 to investigate the role of anti-MBG mAb treatment, administered in vivo 1 week before the ex vivo studies, on the relaxation of aortae. The force of contractions was expressed as the percent of the vasoconstrictor response to 80 mmol/L KCl (Ugo Basile, Isolated Organ Baths system with 7006 Isometric Transducers and DataCapsule-Digital Recorder). The percent relaxation was calculated relative to the plateau of contractile force that was achieved in response to 100 nmol/L endothelin-1.