Evaluation of the Effect of Aging on Intracellular Free Potassium, Magnesium and Calcium in Rats: Relation to Hypertension and Diabetes

Altered cytosolic free calcium (Cai), potassium (Ki), magnesium (Mgi) are observed in both hypertension and non-insulin-dependent diabetes mellitus (NIDDM). These observed alterations are also related to extracellular ionized calcium, potassium and magnesium levels in such cases. Because the changes of vascular function and insulin sensitivity in these conditions resemble the changes associated with normal aging, we wondered to what extent similar alterations in calcium, potassium and magnesium metabolism can occur with aging per se in the absence of hypertension or diabetes. We therefore measured platelet Cai, Ki and Mgj levels and serum Ca, K, Mg-ion levels in normotensive, non-diabetic aged rats and compared the obtained results with their corresponding values in normotensive, non-diabetic young rats, and in both young hypertensive and young diabetic rats. Platelet Cai levels were higher (125.9±8.1 versus 98.9±1.4 nmol/L) and serum Ca-ion levels lower (8.9±0.2 versus 10.3±0.28 mg/dl) in aged compared with young control rats. Furthermore, platelet Ki and Mgi levels were lower (131±2.4 versus 14613.8 mmol/1; 218.419.4 µmol/l versus 326.319.8 µmol/1) in aged compared with young control rats. Serum K-ion and Mg-ion levels were also lower (4.410.18 versus 5.410.15 mmol/1; 1.5810.08 versus 1.92±0.3mg/dl) in aged compared with young control rats. These ionic changes mimic those occuring in young hypertensive and young diabetic rats. We conclude that aging is associated with alterations of cytosolic Cai, Ki, Mgi and serum Ca-ion, K-ion, Mg-ion levels resembling those changes present at any age in hypertension and diabetes. We hypothesize that these alterations of ionic concentrations underlie the predisposition to the alterations of blood pressure and insulin sensitivity characteristic of normal aging.