Uptake and binding of labeled corticosterone by the salt gland of the duck ( Anas platyrhynchos)

Abstract

Tritiated corticosterone was injected ip into young mallard ducks and the birds were sacrificed at various time intervals thereafter up to 3 hr. There were no differences in rate of change in the concentration of tritium in the blood and salt glands of these animals. Following perfusion, however, the rate of change in the glands was much slower than that of the blood, indicating that the glands take up and retain significant amounts of labeled material and that true uptake and retention probably cannot be demonstrated in salt glands without removal of the radioactivity in the blood. Pretreatment with dexamethasone did not significantly inhibit the in vivo uptake of radioactivity by salt glands of birds maintained on a freshwater regimen, but did inhibit isotope retention by 72% in ducks previously adapted to hypertonic saline in their drinking water. In addition, cytosols from salt glands bound over 12 and 33 times more radioactivity in vitro than did the hippocampus and hypothalamus, respectively. These studies indicate that the salt glands of euryhaline birds take up, retain, and appear to selectively bind labeled material after injection of tritiated corticosterone. The data suggest that the salt gland is most likely a glucocorticoid target organ and that exposure to a salt water environment probably stimulates enhanced synthesis of steroid receptors in salt glands.