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Published on: July 3, 2013
Binding sites for atrial natriuretic peptide on platelets in patients with congestive cardiomyopathy
Insights
Platelet atrial natriuretic peptide (ANP) receptors are not down-regulated in patients with congestive cardiomyopathy, despite chronically elevated ANP plasma levels. This suggests ANP receptor number remains stable in these cardiovascular conditions.
Area of Science:
- Cardiology
- Endocrinology
- Molecular Biology
Background:
- Atrial natriuretic peptide (ANP) plays a crucial role in cardiovascular homeostasis.
- Elevated ANP levels are observed in conditions like congestive cardiomyopathy.
- Platelets possess ANP binding sites, but their regulation in disease is not fully understood.
Purpose of the Study:
- To investigate whether ANP binding sites on platelets are down-regulated in patients with chronically elevated ANP plasma levels.
- To compare ANP receptor density and affinity in patients with congestive cardiomyopathy versus healthy controls.
Main Methods:
- Quantification of ANP binding sites on platelets using a radioligand assay.
- Measurement of plasma ANP and cyclic guanosine monophosphate (cGMP) levels.
- Comparison between 15 adult patients with congestive cardiomyopathy and 18 healthy volunteers.
Main Results:
- Patients exhibited significantly higher plasma ANP and cGMP levels compared to healthy volunteers.
- No significant difference was found in the number of ANP binding sites per platelet between patients and controls.
- Dissociation constants for ANP binding were similar in both groups, indicating no change in receptor affinity.
Conclusions:
- Platelet ANP receptor density is not reduced despite chronically elevated ANP plasma levels in patients with congestive cardiomyopathy.
- The number and affinity of ANP binding sites on platelets appear to be maintained even in the presence of high circulating ANP concentrations.
Abstract:
The aim of the present investigation was to evaluate a possible down-regulation of atrial natriuretic peptide (ANP) binding sites on platelets in patients with chronically elevated ANP plasma levels. The assay procedure was proved to be able to measure the total number of binding sites even in the presence of high ANP plasma levels. We studied 15 adult patients with congestive cardiomyopathy in comparison to 18 healthy volunteers. In the patients the median ANP plasma level (median = 375, range: 155-900 pg ml-1) was about six-fold higher than in the healthy volunteers (median: 55.5, range: 20-90 pg ml-1). The median cyclic guanosine monophosphate (cGMP) plasma level (median: 6.2, range: 2.5-21.4 pmol ml-1) was about three-fold higher than in the healthy volunteers (median: 1.8 range: 1-2.8 pmol ml-1). Despite these markedly elevated ANP and cGMP plasma levels we did not find significantly less receptors per platelet in the patients (median: 19, range: 7.2-60.2) than in the healthy volunteers (median: 24.5, range: 14.8-41.1). Furthermore, there was no difference in the dissociation constants between the patients (median: 10.5, range: 7.9-27.4 pmol l-1) and the control subjects (median: 8.9, range: 5.4-17 pmol l-1).
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