Cellular ionic alterations with age: Relation to hypertension and diabetes

BACKGROUND: Cytosolic free calcium (Cai) and magnesium (Mgi) are vital to c ellular homeostasis and function. OBJECTIVE: To evaluate cellular divalent cations in normal subjects at diff erent ages and their relationship to ion levels in essential, hypertension and diabetes. DESIGN: A cross-sectional study. SETTING: A university hospital in New York. PARTICIPANTS: A total of 103 subjects (32 older, 71.1 +/- 1.2 y/o, and 71 y oung/middle aged subjects, 51.1 +/- 2.3 y/o). INTERVENTION: Oral glucose tolerance test. MEASUREMENTS: F-19 and P-31 NMR spectroscopy were used to measure Cai and M gi levels in erythrocytes from normal (>65 y/o, n = 11; <65 y/o, n = 26), h ypertensive (EH) (>65 y/o, n = 9; <65 y/o, n = 30), and type 2 diabetic (DM ) (>65 y/o, n = 12; <65 y/o, n = 15) subjects; these levels were also compa red with glucose and insulin levels before and after oral glucose loading. RESULTS: Fasting Mgi levels were lower (207 +/- 7.8 vs 236 +/- 7.5 mu M; P < .05) and Cai higher (32.2 +/- 3.0 vs 20.3 +/- 1.8 nM; P < .05) in older t han in younger normal subjects. For all normal subjects, the greater the ag e, the higher the Cai (r = 0.622, P = .004) and the lower the Mgi (r = -0.4 23; P = .011). However, no significant (P = NS) differences in Mgi or Cai l evels were observed between older normal and young/middle-aged subjects wit h EH (Mgi = 189.7 +/- 5.9 vs 182.6 +/- 9.8 mu M; Cai = 33.8 +/- 4.9 vs 35.6 +/- 4.0 nM) or DM (Mgi = 182.8 +/- 10.9 vs 180.8 +/- 8.1 mu M; Cai = 33.6 +/- 4.3 vs 39.7 +/- 5.9 nM). Significant relationships were also found betw een cellular ion content, blood pressure, and glycemic indices. CONCLUSIONS: Aging is associated with the onset of altered Cai and Mgi leve ls, indistinguishable from those observed in hypertension and diabetes, ind ependent of age. We suggest that these ionic changes may be clinically sign ificant, underlying the predisposition of older subjects to cardiovascular and metabolic diseases.