Plasma Atrial Natriuretic Peptide Concentrations and Associated Factors in Captive Dolphins: Potential Implications for Cardiovascular Assessment

This exploratory study evaluated plasma atrial natriuretic peptide (ANP) concentrations in four species of captive cetaceans and their associations with physiological and environmental factors, including husbandry conditions, diet, and management practices. Twenty-six individuals were voluntarily sampled, and blood samples were analyzed using a human-based chemiluminescent immunoassay. Transthoracic echocardiography was also attempted in several individuals but was technically challenging due to interference from the lung tissue and the sternum. The mean plasma ANP concentration in clinically healthy young animals was 44.12 ± 14.62 pg/mL, with no significant differences observed according to age, sex, species, or the presence of mild chronic disease. ANP was detectable across all species using human reagents. In addition, brain natriuretic peptide (BNP), a commonly used cardiac biomarker in humans and other animals, was evaluated for comparison; however, BNP concentrations remained below the detection threshold, possibly reflecting species-specific differences. Importantly, ANP concentrations were not evaluated in animals with clinically significant disease, and therefore the relevance of these findings to diseased populations remains unknown. These results demonstrate that plasma ANP can be measured using existing clinical assays and provide preliminary baseline data for multiple cetacean species. Overall, ANP may offer preliminary insights into physiological variation in managed cetaceans; however, its utility as a biomarker for cardiovascular or systemic health assessment remains to be determined.