STUDIES WITH LABELLED ANTERIOR PITUITARY PREPARATIONS: ADRENOCORTICOTROPIN

Abstract

Tracer studies with labelled prepns. of anterior pituitary hormones ACTH[long dash]an adrenocorticotropic hormone (Armour ACTH) prepn. labelled by iodination with I131 was administered intracardially to normal male Sprague-Dawley rats. Several organs were assayed for radioactivity at various time intervals following injn. It was observed that a max. concn. of radioactivity was demonstrable in the adrenals immediately after intracardiac injn. of the hormone prepn. The level of radioactivity in the adrenals was observed to decrease rapidly until,at the end of 2 hrs., practically no radioactivity was detected. Radioautographs of the adrenals after admn. of iodinated ACTH have shown a predominance of radioactivity in the cortex. Control studies with inorganic radioactive iodine and serum albumin labelled with I131 reveal curves unlike those obtained with labelled ACTH. Serum albumin labelled with I131 shows only slight disappearance from the adrenals after 4 hrs. After the intracardiac admn. of inorganic I131, radioactivity can be detected in the adrenals up to 6 hrs. In no case was the degree of localization of labelled ACTH approached by any of the controls.