1. To obtain additional information on the role of the ionic composition of the vascular wall in the pathogenesis of arterial hypertension, we studied the distribution of ions in aorta and tail arteries of rats with experimental renal hypertension.
2. The water content of rat aorta is markedly increased in hypertensive animals [1992 ml/kg-dry weight (DW) compared with 1688 ml/kg DW].
3. Na, K, Ca, Mg and to a less extent Cl content is increased in both aorta and tail arteries.
4. These modifications are not affected by incubation in vitro.
5. Compartmental analysis as well as pharmacological studies suggest that part of the water increase and most of the potassium excess are related to a hypertrophy of smooth-muscle cells in hypertensive arteries.
6. The sodium excess in the vessels of hypertensive rats is bound in the extracellular space on anionic sites.
7. From these observations, it seems unlikely that the ionic modification described could affect the membrane potential of smooth-muscle cells, since the ratio between extra- and intra-cellular concentration is not markedly affected.
8. The bound sodium could affect the viscoelastic properties of the arteries of hypertensive animals. Cell hypertrophy by itself could explain at least partly the modification of the ionic composition and the increased reactivity of hypertensive vessels.