Systolic blood pressure alterations during hyperinsulinemia are related to changes in ionized calcium status

Background: A correlation between changes in ionized calcium status and changes in systolic blood pressure (BP) has previously been observed during induced euglycemic hyperinsulinemia in patients with essential hypertension. The objective of this study was to evaluate associations between alterations in ion status and BP changes during euglycemic hyperinsulinemia in healthy normotensive subjects. Methods: Ion status in plasma and BP were measured before and at the end of euglycemic hyperinsulinemic clamp tests performed in 41 healthy normotensive volunteers. Results: During euglycemic hyperinsulinemia plasma sodium increased by 1% (P< .0001), ionized calcium (iCa) by 5% (P< .0001), and ionized magnesium (iMg) by 4% (P< .01), whereas potassium decreased by 10% (P< .0001). The changes in plasma iCa and iMg correlated significantly to changes in systolic BP (r = −0.38, P< .02; R = −0.32, P< .05, respectively), but the correlation between changes in iMg and changes in systolic BP did not remain significant in a multiple regression model. The glucose infusion rate correlated inversely to the change in iMg (r = −0.39, P< .01). Conclusions: The group mean systolic BP was unaltered during induced euglycemic hyperinsulinemia in healthy normotensive subjects; however, a more pronounced increase in the circulating iCa concentration was associated with a greater decline in systolic BP, which is in accordance with previous observations in patients with essential hypertension. The group mean diastolic BP was decreased; however, the lowered diastolic BP was not correlated to changes in ion status.