Antidiuretic hormone (ADH) is manufactured in the hypothalamus, contributing to regulation of plasma osmolality and blood pressure. Excessive levels may play a role in the development of congestive heart failure (CHF). Previously, ADH has been measured by radioimmunoassay, which may be expensive and not feasible for clinical practice. Because human and canine ADH structures are homologous, authors postulated that the use of a human enzyme immunoassay (EIA) kit would be useful to quantify canine ADH levels. Plasma samples from 6 healthy dogs were used to validate the EIA kit for measurement of ADH levels by evaluating intraassay precision, dilutional linearity, and spiking recovery. The EIA kit was not as sensitive at detecting low levels of ADH as radioimmunoassay. However, all 3 variables showed comparable concentrations of ADH to those measured by radioimmunoassay in normal dogs and humans.
ADH concentrations were then measured and compared in 6 healthy dogs and 12 dogs with CHF. Although high circulating levels of ADH have been reported in humans with heart failure, relatively little data exist regarding ADH levels in dogs with heart disease. Median plasma concentration of ADH in dogs with CHF was 6.15 pg/mL, which was significantly higher than that measured in healthy dogs (3.67 pg/mL). This study demonstrated the utility of the EIA for determining ADH concentrations in dogs and provides the basis for future studies determining ADH concentrations in dogs with heart disease, as well as in evaluating these levels in light of plasma osmolality and sodium levels.