Blood Pressure Changes in Relation to Sodium and Calcium Status in Induced Hyperinsulinemia

Insulin increases renal sodium reabsorption which may contribute to hypertension. However, acute insulin administration may result in vasodilation. The aim of the present study was to investigate effects on blood pressure and alterations in ion status during hyperinsulinemia. Blood pressure and serum sodium and ionized calcium concentrations were measured before and at the end of euglycemic hyperinsulinemic clamp tests performed in 45 patients with essential hypertension. Both the systolic and the diastolic blood pressure decreased, by 4% (p < 0.05) and 3% (p < 0.05), respectively. Circulating ionized calcium concentration increased by 2% (p < 0.001), and the ratio between circulating sodium and ionized calcium concentrations decreased. The changes in circulating sodium concentration correlated to changes in systolic blood pressure (SBP; r = 0.36, p = 0.05). Both ionized calcium concentrations and the ratio between circulating sodium and ionized calcium concentrations correlated to changes in SBP during hyperinsulinemia (r = -0.41, p = 0.03, r = 0.56, p < 0.01, respectively). The changes in ion status were not significantly correlated to age, body mass index or insulin sensitivity. In conclusion, a more pronounced increase in circulating ionized calcium concentration and reduction in the ratio between sodium and ionized calcium concentrations was associated with a greater blood pressure decline during the hyperinsulinemic clamp test when performed in hypertensive patients.