The distribution of sodium in aortic walls from spontaneously hypertensive and normotensive rats.

The contents of exchangeable sodium, bound sodium and total water and the extracellular space of thoracic aortas from normotensive and spontaneously hypertensive rats were measured. The aortas from the hypertensive rats contained more sodium than those from the normotensive animals while the total water content and extracellular space in the two groups were the same. The capacity to bind sodium in an osmotically inactive form was greater in the aortas from the hypertensives than in those from the normotensives. The difference in binding capacity was of the same order of magnitude as the difference in sodium content, indicating that the excess sodium in the thoracic aortas from the hypertensive rats was osmotically inactive and thus unable to cause water logging.