Evaluation of the effect of aging on intracellular free potassium, Magnesium and Calcium in rats: relation to hypertension and diabetes

ABSTRACT

Altered cytosolic free calcium [Ca[i]], potassium [K[i]], magnesium [Mg[i]] 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 Ca[i] K[i] and Mg[i] levels and serum Ca, K, Mg-ion levels in normotensive, non-diabetic aged rats and compared the obtained results with their corre sponding values in normotensive, non-diabetic young rats, and in both young hypertensive and young diabetic rats. Platelet Ca[i] 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 K[i] and Mg[i] levels were lower [131 +/- 2.4 versus 146 +/- 3.8 mmol/l; 218.4 +/- 9.4 micro mol/l versus 326.3 +/- 9.8 micro mol/l] in aged compared with young control rats. Serum K-ion and Mg-ion levels were also lower [4.4 +/- 0.18 versus 5.4 +/- 0.15 mmol/l; 1.58 +/- 0.08 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 Ca[i], K[i] Mg[i] 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 tire alterations of blood pressure and insulin sensitivity characteristic of "normal" aging