Endothelium Function Is Protected by Albumin and Flow-Induced Constriction Is Independent of Endothelium and Tone in Isolated Rabbit Femoral Artery

Abstract

To investigate the preservation of endothelial function, we perfused two segments of one rabbit femoral artery (n = 8) in a pressure myograph in parallel, both with Tyrode, but one with 0.6% albumin added. The change in the outer diameter of the vessels [preconstricted with norepinephrine (NE) to 70%] in response to acetylcholine as an indicator of the endothelial function, was repeatedly measured over 5 h after the equilibration. The difference between the acetylcholine responses of the two vessel segments was significant (p < 0.05) after a perfusion period of 4 h. We also investigated whether flow-induced constriction is dependent on (1) the presence of endothelium and (2) the level of preconstriction. We therefore perfused segments of rabbit femoral arteries (n = 5) with Tyrode with 0.6% albumin. If acetylcholine-induced dilatation was present, a flow-diameter relation was determined at two constriction levels: about 60% (high) and 90% (low) of the passive outer diameter. Both determinations were repeated after mechanical endothelium removal (checked functionally and histologically). A similar decrease in diameter (about 7%) with an increase in flow ranging from 0 to 1,330 microliters/min was found in all conditions. We conclude that the addition of (0.6%) albumin protects endothelial function in the rabbit femoral artery when perfused in the low-flow range for a period longer than 4 h. We also found that flow-dependent constriction is neither influenced by the presence of the endothelium nor by the level of tone induced with NE.

Responses to mechanical stimuli of isolated basilar and femoral arteries of the rhesus monkey are different

“…Bovine albumin(A-7030, essentially fatty acid free), added to the perfusate was used in all experiments to keep the endothelium intact [15]. This gas mixture kept the pH between 7.32 and 7.38 and the PO2 between 155 and 165mmHg (measured with an Instrumentation Laboratory no.…”

“…The rabbit femoral artery, when constricted with norepinephrine, further constricted with increasing flow independent of the endothelium [15]; however, with potassium preconstriction, this vessel showed a dilation followed by a constriction with increased ftow [19]. This dilation could be abolished with an NO synthase blocker and the flow-diameter relations during norepinephrine and potassium would then be similar.…”

Smooth muscle responses of the rat septal artery are not influenced by surrounding passive cardiac tissue

“…This solution contained (in mM): NaC1 128.3, KC1 4.7, CaC12 1.36, MgC12 1.05, NaHCO3 20.2, NaH2PO 4 0.42, and glucose 11.1; it was gassed with 5% CO2, 20% 02, and 75% N» The gas mixture kept the pH between 7.30 and 7.40. Albumin (0.6%) was then added to the perfusion solution to protect the endothelium [8]. In both protocols KC1 (125 mM) was applied bõth on the inside and the outside of the vessel.…”

“…The contribution of the endothelium was not studied separately, but we took precautions to protect it from being damaged [8]; the factors that affect the endothelium, flow and transmural pressure, were the same in each experiment.…”

Continuous flow augments reactivity of rabbit carotid artery by reducing bioavailability of NO despite an increase in release of EDHF

“…Middle cerebral arteries of the rat constrict when exposed to flow, a response that is attenuated in the presence of the endothelium (5). Likewise, in rabbit femoral arteries, flow causes a constriction (4,15,31). The reason for these apparent discrepancies include differences in experimental protocols where little attention has been paid to dissociate flow-induced circumferential stretch (evoked by an increased flow as a result of an increase in perfusion pressure) from the effect of flow (shear stress) per se.…”