Effects of magnesium and nifedipine infusions on insulin action, substrate oxidation, and blood pressure in aged hypertensive patients.
Eight aged (70.1 +/- 2.1 years), nonobese (body mass index [BMI] = 26.3 +/- 0.4), hypertensive (systolic blood pressure [SBP] = 184 +/- 4.1; diastolic blood pressure [DBP] = 105 +/- 2.4 mm Hg) subjects underwent a euglycemic hyperinsulinemic (7.1 pmol/kg x min during 240 min) glucose clamp with four different infusions: a) 0.9% NaCl; b) 1.0 micrograms/kg x min nifedipine; c) 100 mumol/min magnesium; d) 1.0 micrograms/kg x min nifedipine plus 100 mumol/min magnesium. All tests were performed in random order. Simultaneous D-3-H glucose infusion and indirect calorimetry allowed us to determine glucose turnover parameters and substrate oxidation. Insulin infusion per se stimulated erythrocyte magnesium (1.83 +/- 0.04 v 1.98 +/- 0.03 mmol/L, P < .03) and calcium (4.7 +/- 0.3 v 6.2 +/- 0.4 mumol/L, P < .02) accumulation, and enhanced total body glucose disposal oxidative and nonoxidative glucose metabolisms. Infusion of insulin and nifedipine v insulin alone reduced insulin-mediated increase in intracellular calcium (5.4 +/- 0.3 v 6.2 +/- 0.4 mumol/L, P < .02), but potentiated the insulin effect upon nonoxidative glucose (15.4 +/- 0.4 v 11.1 +/- 0.3 mumol/kg lean body mass [LBM] x min, P < .03) metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)
Paolisso
G
G
Department of Geriatric Medicine and Metabolic Diseases, II University of Naples, Italy.
Gambardella
A
A
Balbi
V
V
Galzerano
D
D
Verza
M
M
Varricchio
M
M
D'Onofrio
F
F
D000368:Aged; D000375:Aging / Q000378:metabolism / Q000502:physiology*; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D015992:Body Mass Index; D002118:Calcium / Q000032:analysis / Q000097:blood; D002151:Calorimetry; D004357:Drug Synergism; D004912:Erythrocytes / Q000737:chemistry; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007328:Insulin / Q000494:pharmacology*; D008274:Magnesium / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D009543:Nifedipine / Q000008:administration & dosage / Q000494:pharmacology*; D010084:Oxidation-Reduction
D001786:Blood Glucose; D007328:Insulin; D008274:Magnesium; D009543:Nifedipine; D005947:Glucose; D002118:Calcium