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Updated: Aug 21, 2026
Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta
Published on: June 10, 2015
Altered calcium signaling in platelets from nitric oxide-deficient hypertensive rats
David Iyú1, Noemí M Atucha, Concepción Martínez-Prieto
1Departamento de Fisiología, Facultad de Medicina de Murcia, Spain. jgestan@um.es
Insights
Chronic nitric oxide inhibition in rats elevates platelet calcium levels, enhancing calcium entry and mobilization. This suggests altered calcium regulation contributes to L-NAME-induced hypertension.
Area of Science:
- Cardiovascular Physiology
- Platelet Biology
- Renal Physiology
Background:
- Nitric oxide (NO) plays a crucial role in regulating vascular tone and platelet function.
- Chronic inhibition of NO synthesis, using N-nitro L-arginine methyl ester (L-NAME), leads to arterial hypertension.
- The impact of L-NAME-induced hypertension on platelet calcium handling remains incompletely understood.
Purpose of the Study:
- To investigate the mechanisms of calcium entry and mobilization in platelets from rats chronically treated with L-NAME.
- To determine if L-NAME-induced hypertension alters basal and stimulated intracellular calcium levels in platelets.
Main Methods:
- Platelets were isolated from rats chronically treated with L-NAME (40 mg/kg/day for 5 days) and control rats.
- Platelets were loaded with fura-2 to measure intracellular calcium levels via fluorescence spectroscopy.
- Calcium levels were assessed under basal conditions, after thrombin stimulation, and in response to calcium addition to thapsigargin-treated platelets.
Main Results:
- Platelets from L-NAME-treated rats exhibited elevated basal intracellular calcium levels, irrespective of extracellular calcium.
- Thrombin stimulation induced greater calcium level elevations in L-NAME-treated rat platelets compared to controls.
- Calcium addition to thapsigargin-treated platelets resulted in a significantly larger calcium increase in platelets from hypertensive rats.
Conclusions:
- Arterial hypertension induced by reduced nitric oxide synthesis alters platelet calcium regulation.
- Elevated baseline calcium levels, enhanced calcium entry, and mobilization are characteristic of platelets from L-NAME-treated rats.
- These alterations may stem from direct or indirect effects of nitric oxide deficiency on platelets or other tissues.
Abstract:
BACKGROUND: In the present study we have analyzed the mechanisms of calcium entry and mobilization in platelets obtained from rats chronically treated with the nitric oxide synthesis inhibitor, N-nitro L-arginine methyl ester [L-NAME, 40 mg/kg/day, 5 days). The platelets were obtained the day of the experiment, washed and loaded with fura-2. The intracellular calcium levels were determined in suspension of cells by means of fluorescence spectroscopy. RESULTS: Basal calcium levels were always elevated in the platelets of the L-NAME-treated rats, both in the presence and in the absence of extracellular calcium. The administration of thrombin in the absence and in the presence of extracellular calcium induced important elevations in calcium levels that were always of greater magnitude in the platelets of the L-NAME-treated rats than in those of the controls. The addition of calcium to thapsigargin-treated platelets produced a massive elevation in calcium levels in both groups that was significantly greater in the platelets obtained from the hypertensive rats than in those of the controls. CONCLUSIONS: It is concluded that the arterial hypertension induced by the reduction of nitric oxide alters the regulation of platelet calcium levels so that elevated baseline levels and calcium entry and mobilization are enhanced. This could be the result of direct or indirect effects of the lack of nitric oxide synthesis in platelets or in other tissues.
