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(Hypertension. 1995;26:1070-1073.)
© 1995 American Heart Association, Inc.

Articles

Calcium-ATPase and Insulin in Adolescent Offspring of Essential Hypertensive Parents

Beatriz Grunfeld; María Gimenez; Miriam Romo; Laura Rabinovich; Rosa B. Simsolo

From the Hypertension Clinic, Children's Hospital "Ricardo Gutierrez," Buenos Aires, Argentina.

Correspondence to Beatriz Grunfeld, MD, Hipertensión Arterial, Hospital de Niños "R. Gutierrez," La Pampa 3635, 1430 Buenos Aires, Argentina.

Abstract A number of abnormalities in calcium homeostasis have been reported in patients with essential hypertension. In turn, insulin has been shown to influence the activity of the Ca²⁺-ATPase. We have previously shown that normotensive offspring of essential hypertensive individuals have an exaggerated insulin response to a glucose overload. Therefore, the aim of the present study was to evaluate basal and calmodulin-activated Ca²⁺-ATPase in red blood cells and its relationship to the insulin response during an intravenous glucose tolerance test in 27 normotensive adolescents with a family history of essential hypertension (F+) (mean age, 13.9±0.5 years) and in 10 control subjects matched for age and body mass index with no family history of hypertension (F-). The results (mean±SD) were as follows (µmol Pi/[mg protein/h]10^-1): basal Ca²⁺-ATPase, 4.5±1.2 in F+ and 5.1±1.6 in F- (P=NS); calmodulin-activated Ca²⁺-ATPase, 13.6±3.9 in F+ and 16.2±1.7 in F- (P<.04). The insulin area under the curve after the glucose load was 3413±1674 µU/mL per hour in F+ and 2752±928 in F- (P=NS). Calmodulin-activated Ca²⁺-ATPase showed a negative correlation with the insulin area under the curve (r=-.59, P<.005) and cholesterol levels (r=-.38, P<.03). Urinary calcium excretion was 1.82±0.9 mmol/d in F+ and 2.47±0.9 mmol/d in F- (P=NS). Our findings indicate a diminished activity of calmodulin-stimulated Ca²⁺-ATPase despite increased levels of insulin, a known activator of this pump, further suggesting the presence of insulin resistance in normotensive offspring of essential hypertensive individuals. Since Ca²⁺-ATPase is an extrusion pump, a drop in its activity may lead to an increase in intracellular calcium accumulation and thus contribute to the development of hypertension.

Key Words: hypertension, essential • adolescent medicine • Ca²⁺-transporting ATPase • insulin