Cardiac vasoactive peptides in hypertrophic cardiomyopathy of cats

Idiopathic hypertrophic cardiomyopathy (HCM) is the most important and common feline heart disease. The nucleotide and amino acid sequence of feline ANP, BNP, ET-1 and VP have been established in our laboratory. Although feline ANP and VP are highly conserved throughout species with the mature peptides being identical, feline BNP and feline ET-1 differ from that of other mammalian species. An immunohistochemistry study showed that ANP and BNP normally co-exist, and are restricted to the atrial cardiomyocytes in healthy cats, with denser staining closer to the endocardial surface. With HCM, this layered pattern is less distinct and BNP appears in the ventricles as well. Endothelin production and/or storage was found throughout the cardiomyocytes in all cardiac regions and no differences were found between control and HCM cats. Vasopressin was not found within the heart tissue, nor the aorta.; The tissue vasoactive peptide concentrations from heart extracts agreed with the immunohistochemical localization of ANP and BNP. Although overall cardiac production of ANP was constant, the majority of BNP production switched from atria to the ventricles. ANP and BNP mRNA expression concurred with tissue peptide levels. ET-1 mRNA was detectable throughout the heart tissue. However, neither mRNA expression nor peptide levels of vasopressin were found in cardiac tissue of normal cats or cats with HCM.; In conclusion, ANP and BNP are normally produced and stored in the atria. With HCM, significant peptide and mRNA expression of BNP is found in the ventricles, while protein and gene expression of ANP remains mainly in the atria. This pattern agrees with increases in plasma concentrations of both peptides in cats with HCM, and suggests that BNP may be a more sensitive and specific plasma marker of feline HCM than ANP. Endothelin is expressed and produced throughout the cardiac tissue. Although plasma concentrations of ET-1 are known to be significantly higher in feline HCM than normal cats, it is probably due to noncardiac sources. The lack of detectable vasopressin expression suggests that vasopressin is not produced in significant amounts in feline cardiac tissue, contrasting with previous studies performed in rats.