Key result
TTR-ANP transgenic mice exhibited similar immunoreactivity for ANP and BNP in the cardiac conduction system compared to wild-type mice, suggesting ectopic ANP does not repress cardiac production.
Why the study?
Does ectopic ANP overexpression alter the expression patterns of natriuretic peptides in the heart of TTR-ANP transgenic mice?
Does ectopic ANP overexpression alter the expression patterns of natriuretic peptides in the heart of TTR-ANP transgenic mice?
Ectopic ANP expression and release do not repress cardiac production of ANP in TTR-ANP transgenic mice.
Answers are grounded in this paper and cite their sources.
Ectopic ANP does not repress cardiac natriuretic peptide production in this model; leaves open regulatory mechanisms in human disease.
The transgenic mice, TTR-ANP, carrying a fusion gene comprising the transthyretin promoter and the atrial natriuretic peptide (ANP) structural sequence, are known to have elevated ANP plasma levels as well as lowered blood pressure levels. On the other hand, it is not known whether these transgenic mice show changed natriuretic peptide (NP) expression patterns in the heart. Therefore, we examined the distribution of NPs in the myocardium and the conduction system of transgenic mice overexpressing ANP, as well as in wild-type littermates. The hearts were serially sectioned and processed for immunohistochemistry, with antisera against ANP and brain natriuretic peptide (BNP). Florescence microscopy was performed for qualitative analysis. Immunoreactivity for ANP and BNP was detected to a similar degree in the conduction system of both transgenic and wild-type mice. The nodal tissues never exhibited immunoreactions for ANP or BNP, whereas Purkinje fibers of the atrioventricular junctional tissue, bundle branches, and the peripheral Purkinje fiber network exhibited specific immunoreactivity. Atrial and ventricular myocytes of both transgenic and wild-type mice exhibited ANP and BNP to a similar extent. This is the first study examining the expression pattern of NPs in the cardiac conduction system of the mouse as well as the pattern of ANP and BNP expression in the conduction system of TTR-ANP transgenic mice and its wild-type siblings. The findings in this study suggest that ectopic ANP expression and release do not repress cardiac production of ANP.
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Lundberg et al. (2005) studied this question. TTR-ANP transgene vs. Wild-type littermates was evaluated on Distribution of ANP and BNP in the myocardium and conduction system. TTR-ANP transgenic mice exhibited similar immunoreactivity for ANP and BNP in the cardiac conduction system compared to wild-type mice, suggesting ectopic ANP does not repress cardiac production.
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