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Atrial natriuretic factor in the freshwater turtle Pseudemys scripta: a partial characterization
1Department of Physiology and Biophysics, University of Illinois, Urbana 61801.
General and Comparative Endocrinology
|November 1, 1994
Summary
This study found that freshwater turtles possess natriuretic and vasorelaxant materials in their heart atria and ventricles. These findings suggest Atrial Natriuretic Peptide (ANP) is a conserved cardiac hormone across reptiles.
Area of Science:
- Cardiovascular Physiology
- Comparative Endocrinology
- Reptilian Biology
Background:
- Natriuretic peptides are crucial for regulating blood pressure and fluid balance.
- Previous research has primarily focused on mammalian and avian natriuretic peptide systems.
- The presence and function of natriuretic peptides in reptiles, particularly Chelonians, remain less understood.
Purpose of the Study:
- To investigate the presence and characteristics of natriuretic and vasorelaxant substances in the heart of the freshwater turtle (Pseudemys scripta).
- To determine if these substances are analogous to mammalian Atrial Natriuretic Peptide (ANP).
- To assess the physiological responsiveness of turtles to ANP.
Main Methods:
- Extraction and partial purification of atrial and ventricular tissues from Pseudemys scripta.
- Assay of natriuretic and diuretic activity in anesthetized rats.
- Relaxation assays using isolated rat aortic ring segments.
- Immunoreactivity testing with mammalian ANP antisera.
- Size exclusion chromatography for molecular weight determination.
- Binding assays using the bovine adrenal glomerulosa ANP receptor.
- Administration of synthetic rat ANP to conscious turtles to measure arterial pressure changes.
Main Results:
- Crude atrial and ventricular extracts exhibited significant natriuretic and diuretic effects in rats.
- Partially purified atrial extracts induced vasorelaxation in rat aortic rings and showed immunoreactivity to ANP antisera.
- The active substance had a molecular weight of 3-5 kDa and similar binding affinity to mammalian ANP.
- Synthetic rat ANP administration lowered arterial pressure in conscious turtles, indicating physiological responsiveness.
Conclusions:
- Both atria and ventricles of the freshwater turtle synthesize and store biologically active ANP-like materials.
- These findings indicate that ANP is a highly conserved and primitive cardiac hormone, present in Chelonian reptiles.
- This study expands our understanding of cardiovascular regulation in reptiles and the evolutionary conservation of ANP.