Absorption Properties of the Intima of the Carotid Artery. ∗

Abstract

In the course of a series of studies on the structure and function of vessel walls it was determined to investigate the absorption properties of the intima by injecting a diffusible substance into the lumen of a closed vessel. Dogs were used as experimental animals and the common carotid artery was the vessel chosen. For the diffusible substance phenolsulphonphthalein was selected because it has no effect upon tissues and, if absorbed, can be readily detected in the urine in small amounts. The carotid sheath was exposed and the artery doubly ligated without opening the sheath. The ligatures were placed as far apart as possible to allow a maximum of absorption surface, but great care was exercised that no branches should be included in the stretch between the ligatures. The dye was injected through a cannula at a constant pressure equivalent to the carotid pressure (determined for each animal on the contralateral vessel). At the termination of the experiment the phenolsulphonphthalein was evacuated and 1% trypan blue was run through the same system at the same pressure to exclude the possibility of leakage in the system. In a series of 7 animals the dye appeared in the urine in all instances. The appearance time varied between 48 and 141 minutes, whereas the appearance time was 4 to 8 minutes in several control dogs to whom 1 cc. of the dye was administered by the usual intravenous route. No obvious explanation of the delay in excretion was apparent, but, as might be expected, analysis of the data shows that the amount of dye absorbed is a function of the length of vessel included between the ligatures.