Autoradiographic demonstration of glucocorticoid receptors in the intermediate lobe of the rat pituitary transplanted to the anterior eye chamber.

Abstract

It is a general belief that the intermediate lobe of the pituitary, in contrast to the anterior pituitary, is devoid of glucocorticoid receptors. However, Antakly et al. (1985) using immunocytochemistry, demonstrated the presence of this receptor in intermediate lobe cells deprived of the hypothalamic innervation. It was the aim of the present study to confirm this finding by auto-radiography, i.e., using an independent method. The neurointermediate lobe of adult male Wistar rats was syngeneic transplanted to the anterior eye chamber. The recipient rats were adrenalectomized 19 days after grafting and injected with [3H]corticosterone 5 days later. After a survival time of 60 min, autoradiograms were prepared by thaw-mount technique and quantitatively evaluated by silver grain counting. Beside the classical targets, anterior pituitary and hippocampal stratum pyramidale, the intraocular transplants showed a nuclear accumulation of radioactivity. This was abolished in rats treated for competition with an excess of unlabelled corticosterone prior to tracer application. No such receptor binding was found in the normotopic intermediate lobe and in the diaphragm studied as a non-target reference. Thus, this study confirmed that the glucocorticoid receptor gene is expressed if the tissue is grafted into an ectopic site.