Increased calcium 45 fluxes in histologically abnormal human ascending aorta

Abstract

Vascular calcium overload occurs during aging and is accelerated by severe diabetes, smoking, and hypertension, associated with vascular structural changes such as coronary artery calcification. We hypothesize that these vascular structural changes might be associated with change(s) in calcium turnover, which might lead to vascular disorders irrespective of age. We therefore studied, in vitro, the flux of Ca in ascending aortic wall obtained from 27 patients aged 7 to 84 years, mean 54.6 (nine women), undergoing aortic valve replacement. No consent other than that for anesthesia and surgery was obtained. Ascending aortic wall was removed from the aortotomy; part was fixed in Bouin’s solution and embedded in paraffin. Then 4mm sections stained with Masson’s trichrome stain were evaluated without knowledge of Ca flux. Adventitia-free aortic segments were bathed in physiologic saline solution containing Ca (296 kBq/ ml) for 120 minutes at room temperature to label the exchangeable Ca, according to the mehtod of Meisheri, Hwang, and van Breemen. Tissues were transferred to ice-cold Ca-free physiologic saline solution for 30 minutes to remove extracellular Ca. They were then incubated overnight in ethylenediaminetetraacetic acid (2 mmol/L) at room temperature. Tissue and effluent were analyzed for Ca in a liquid scintillation counter. Ca net uptake is expressed as nanomoles per milligram weight. The ratio of Ca total uptake by the tissue to Ca concentration in the incubating bath, the distribution volume, was calculated. Ca efflux was expressed as percent total efflux, and efflux rate constant (per minute) was calculated from the total counts lost from the tissue during each washout period divided by the total counts remaining in the tissue segment. Results were expressed as means 6 standard error. The significance of the differences between means was determined by the Student’s t test (A. Tedgui). Histologic findings in nine patients aged 26 to 83 years (mean 61.9 years) were “normal for age” (Fig. 1). In 18 patients aged 7 to 86 years (mean 52.9 years) histologic findings were considered abnormal (Fig. 2). The net uptake of Ca was significantly higher in samples of ascending aorta histologically abnormal than in those histologically normal for age: 365 6 36.8 nmol/mg tissue (n 5 18) versus 244 6 37 nmol/mg tissue (n 5 9, p , 0.05). The distribution volume for calcium in histologically abnormal tissue was significantly greater than in tissues normal for age: 2.4 6 0.27 (n 5 18) versus 1.9 6 0.27 (n 5 9, p , 0.05). Efflux of Ca from the ascending aorta as percent of total as a function of time was 32.6% 6 4.5% (n 5 18) versus 17.8% 6 3.5% (n 5 9, p , 0.04) at 1 and 2 minutes. Ca efflux rate constant was significantly