Morphology and metabolism of an aortic intima media preparation in which an intact endothelium is preserved

Abstract

An in vitro preparation of rabbit aortic 'intima media' was studied by electron microscopy (EM). Under conditions now in common use, marked alterations in endothelial cell structure were present, including loss of cell integrity. The vascular smooth muscle cells retained a normal EM appearance. A method was developed to prepare segments of rabbit aortic intima media with an intact endothelium resembling that observed in tissue fixed in situ. During a 1 hr incubation with 5 mM glucose in KRB, pH 7.4, gas phase 5% CO2/95% O2, containing 6% bovine serum albumin, the intact aortic intima media preparation retains an essentially unmodified EM appearance and exhibits linear rates of respiration. Under these conditions the intact aortic intima media preparation exhibits significantly higher rates of O2 uptake and glucose uptake than those observed in previous preparation or in other reported aortic intima media preparations. The intact aortic intima media does not exhibit the high rate of aerobic glycolysis during in vitro incubation which has been considered characteristic of the metabolism of rabbit, rat, and swine aortic intima media. In addition, the magnitude of the Pasteur effect was far greater than that observed in other such preparations. The data suggest that the component cells may derive a major fraction of their energy requirements from respiration; they raise further questions concerning the significance of the high rate of aerobic glycolysis observed when these preparations are incubated in vitro, and they suggest that documentation of the EM appearance of the endothelium in such preparations is desirable.