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Parathyroid hormone and platelet cytosolic calcium concentration in essential hypertension
E Poch1, P Fernández-Llama, A Botey
1Nephrology Service, Hospital Clinic I Provincial, University of Barcelona, Catalonia, Spain.
Insights
Essential hypertension is linked to altered calcium levels and higher parathyroid hormone (PTH). Hypertensive patients show increased platelet calcium, correlating with blood pressure, but not PTH.
Area of Science:
- Cardiovascular Medicine
- Endocrinology
- Biochemistry
Background:
- Essential hypertension is a complex condition with multifactorial origins.
- Calcium homeostasis and parathyroid hormone (PTH) play roles in cardiovascular regulation.
- Platelet activation and intracellular calcium concentration ([Ca2+]i) are implicated in hypertension.
Purpose of the Study:
- To investigate the relationship between blood pressure, serum parathyroid hormone (PTH), and platelet cytosolic calcium concentration ([Ca2+]i) in patients with essential hypertension.
- To compare these parameters between hypertensive patients and normotensive controls.
Main Methods:
- Studied 17 patients with essential hypertension and 17 normotensive controls.
- Measured serum ionized calcium and intact PTH levels.
- Quantified resting and thrombin-stimulated platelet [Ca2+]i using spectrofluorimetry with Fura-2 acetoxymethylester.
- Assessed correlation between blood pressure (mean arterial pressure - MAP), PTH, and [Ca2+]i.
Main Results:
- Hypertensive patients had lower serum ionized calcium and higher serum intact PTH compared to controls.
- Resting and thrombin-stimulated platelet [Ca2+]i were elevated in hypertensive patients.
- Thrombin-induced [Ca2+]i increment correlated with MAP in hypertensive patients.
- No significant correlation was found between serum PTH and platelet [Ca2+]i in any group.
Conclusions:
- Essential hypertension is associated with dysregulation of calcium homeostasis and elevated PTH.
- Increased platelet calcium responsiveness in hypertension may contribute to the pathophysiology.
- Platelet [Ca2+]i, but not serum PTH, shows a relationship with blood pressure in essential hypertension.
Abstract:
To investigate the possible relationships between blood pressure, parathyroid hormone (PTH) and platelet cytosolic Ca2+ concentration ([Ca2+]i) in patients with essential hypertension, we studied 17 patients with this disease aged 48 +/- 2 years and 17 normotensive controls aged 44 +/- 3 years. Platelet [Ca2+]i was measured by spectrofluorimetry using the dye Fura-2 acetoxymethylester. Patients with essential hypertension displayed lower levels of serum ionized Ca2+ (0.99 +/- 0.03 versus 1.1 +/- 0.01 mmol/l, P < 0.05) and higher serum intact PTH levels (37 +/- 3 versus 26 +/- pg/ml, (P < 0.01) than the normotensive controls. Although serum levels of intact PTH were significantly correlated with mean arterial pressure (MAP) in the combined group of subjects (r = 0.42, P < 0.05), there was no correlation when each group was considered separately. Resting platelet [Ca2+]i was also higher in patients than in controls (57 +/- 3 versus 48 +/- 2 nmol/l, P < 0.005). When platelets were stimulated in vitro with thrombin, the increment in [Ca2+]i was also greater in patients than in controls in the presence of extracellular Ca2+ (264 +/- 24 versus 194 +/- 19 nmol/l, P < 0.05) but not in its absence (123 +/- 12 versus 112 +/- 10 nmol/l). The thrombin-induced increment in [Ca2+]i was correlated with MAP in the hypertensive patients (r = 0.64, P < 0.01) and in the combined group of subjects (r = 0.42, P < 0.05). There was no relationship between resting or thrombin-induced [Ca2+]i and serum PTH in either group of patients or in the combined group of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)