Subacute infusion of physiological doses of parathyroid hormone raises blood pressure in humans |
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Authors: | Fliser D; Franek E; Fode P; Stefanski A; Schmitt C; Lyons M; Ritz E |
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Institution: | Departments of Internal Medicine and Pediatrics, Ruperto-Carola University, Bergheimstrasse 56a, 69115 Heidelberg, Germany; Corresponding author |
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Abstract: | Background. Acute administration of parathyroid
hormone (PTH) causes vasodilation and blood pressure decrease in
experimental animals. This effect contrasts with the putative role of
secondary hyperparathyroidism in the pathogenesis of hypertension of
patients with renal failure. Uraemia is characterized by insulin resistance
and hyperinsulinaemia. We therefore investigated whether subacute
administration of physiological doses of human 1,34-PTH affects blood
pressure under conditions of controlled insulin levels (euglycaemic clamp
technique) in humans. Methods. In a double-blind
cross-over design 10 healthy male subjects received, on two occasions, in
random order, for 2 h, either a sham infusion or an infusion of 200 units
of 1,34-PTH. Results. Mean ionized calcium
concentration increased significantly (P <0.01)
within the normal range during euglycaemic hyperinsulinaemia, both with
sham infusion (from 1.25 ± 0.04 to 1.29 ± 0.02
mmol/l) and with infusion of 1,34-PTH, but the increase was more marked
with 1,34-PTH administration (from 1.26 ± 0.05 to 1.33
± 0.07). In addition, mean platelet intracellular calcium
concentration (by fluorescence spectroscopy) was unchanged with sham
infusion (49.9 ± 4.1 versus 50.3 ± 5.0 nmol), but
increased significantly (P <0.05; paired
t-test) after 1,34-PTH infusion (from 49.8
± 5.0 to 52.8 ± 5.8). The infusion of 1,34-PTH
resulted in a significant (P <0.01) increase in
mean MAP (from 84 ± 5 to 88 ± 5 mmHg) as compared
with sham infusion (85 ± 4 versus 86 ± 4). The
intra-individual changes in intracellular calcium concentration
(&Dgr;Ca2+]I) were significantly correlated to
the changes in mean MAP (&Dgr;MAP) (r = 0.87,
P <0.001). In contrast to blood pressure,
insulin sensitivity was not affected by 1,34-PTH infusion (M-value: 7.2
± 1.6 mg/kg per min) as compared with sham infusion (7.3
± 1.4). Conclusion. Subacute administration
of physiological doses of parathyroid hormone under hyperinsulinaemic
conditions significantly affects intracellular calcium and blood pressure
in healthy subjects, but does not affect the action of insulin. |
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Keywords: | |
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