The influence of age on fluid and sodium chloride distribution in rat aortic wall

Fluid, Na+ and Cl- content and distribution have been examined in incubated segments of thoracic and abdominal aorta from male Wistar rats aged 1, 3 and 18 months. Na+ and Cl- were determined under conditions of total metabolic blockade (cyanide + iodoacetate). The total aortic mural fluid content, relative to solute-free dry weight, fell from 1 to 3 months, due mainly to relative contraction of the extracellular (e.c.) (inulin) space. It increased from 3 to 18 months due mainly to an increased intracellular (i.c.) (non-inulin) space. Total mural free and bound Na+ content, as well as i.c. Na+ content and concentration, fell from 1 to 3 months and increased from 3 to 18 months. No bound Na+ was detectable in segments which had been incubated in the presence of chondroitinase ABC. I.c. Cl- content and concentration fell from 1 to 3 months, but thereafter did not alter significantly. Bound Cl- in the aortic wall of 3-month-old rats was markedly reduced by incubation in the presence of a non-specific protease preceded by treatment with glycerol. The results are discussed in relation to previously established age-related characteristics of aortic and arterial walls.