Influence of several methodological procedures utilized to obtain in vitro vascular preparations on endothelial activity.
Several maneuvers usually employed to set up isolated vascular preparations could effect the endothelium-dependent relaxation (EDR). The effects of five such maneuvers were studied in rings of rat aorta: 1) Type of anesthesia, 2) Cold storage of the vessels, 3) Length of the stabilization period, 4) Repeated contractions during stabilization, and 5) Performance of washouts during stabilization. Repeated contractions with norepinephrine (NE) 0.1 microM after stabilization altered neither the contraction nor the EDR induced by acetylcholine (Ach) 1 microM. Pentobarbital anesthesia and cold storage of the preparations for 24 h significantly decreased the EDR without effecting the contractile response of the rings. The absence of washouts during stabilization increased the contractions to either NE 0.1 microM or KCl 80 mM by nearly 50%. This increase was prevented by endothelial disruption or, in the presence of intact endothelium, by repeated washouts or by incubation with Bosentan 22 microM. It is concluded that 1) Anesthesia of the animals and cold storage of the preparations can alter the EDR even in the absence of contractile changes in the smooth muscle, and 2) Accumulation of endothelin during the incubation period, even if not producing changes in the resting tension, can substantially alter the subsequent response to vasoactive interventions.