Selenium in the anterior pituitary of the rat after a single injection of 75Se sodium selenite.

In order to investigate the selenite metabolism in the anterior pituitary and compare it with other endocrine organs, rats were injected intraperitoneally with 75Se sodium selenite (5 mg/kg). The rats were whole body counted shortly after injection and recounted just before sacrifice, which was performed 2, 24, 48 h, and 4, 10, 20, 30, 40, 60, and 80 d after injection. Besides the anterior pituitary, the selenium content was also estimated in the thyroid gland, testis, adrenals, liver, kidney, and blood. The maximum selenium content was observed in all organs 2 h after injection, at which time the anterior pituitary contained 2.9 micrograms/g wet wt, compared to 13.5 micrograms/g wet wt in liver and .6 micrograms/mg wet wt in testis. The excretion of selenite from the anterior pituitary resembled that seen in most other organs investigated, i.e., an initial rapid excretion and a slower secondary phase resembling a first order reaction. Practically all selenium was excreted by 60 d after injection. The selenium content in pituitaries from untreated rats was estimated by PIXE analysis to be 2.2 +/- .1 micrograms dry wt and .48 +/- .03 micrograms/g wet wt. From the present study it can be concluded that selenium in the form of selenite accumulates in the anterior pituitary after a single intraperitoneal injection; selenite is excreted from the gland in a biphasic manner; practically all selenium is excreted within 60 d; and pituitaries from normal rats contain .48 micrograms selenium/g wet wt.