The BIO 14.6 strain of hamster is a model of familial cardiomyopathy complicated by congestive heart failure, sodium retention, and edema. In previous studies, bioassay techniques have demonstrated that the cardiac content of atrial natriuretic peptide (ANP) is reduced in these animals. On the basis of this observation, the syndrome of congestive heart failure has been hypothesized to be due to a deficiency in ANP. The current study was designed to correlate the cardiac content of ANP (determined by immunohistochemical techniques) with plasma circulating ANP (determined by radioimmunoassay). α-ANP antibodies were used for both determinations. The content of ANP in the atria was based on the degree of immunoreactive staining present (1 = lowest; 5 = highest), as graded by two observers. The mean granularity score of the cardiomyopathic hamsters was decreased (2.1 ± 0.3) in comparison with that of age- and sex-matched control animals (3.5 ± 0.5; P<0.05). In contrast, circulating immunoreactive ANP was higher in the hamsters with congestive heart failure than in the control animals—185.5 ± 27.2 pg/ml versus 77.7 ± 10.8 pg/ml (P<0.005). This study demonstrates that an inverse relationship exists between ANP content in the atria and circulating ANP. Furthermore, this study suggests that these hamsters with congestive heart failure are not deficient in ANP; rather, secretion of ANP is stimulated and storage of the peptide, represented by atrial granularity, is reduced.
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