Cytodifferentiation and immunocharacteristics of adenohypophysial cells in the toad, Bufo melanostictus

Abstract

Employing the unlabelled antibody enzyme technique cytodifferentiation, immunocharacteristics and topographical distribution of melanotropic (MSH), adrenocorticotropic (ACTH), thyrotropic (TSH), prolactin (PRL), gonadotropic (GTH) and growth hormone (GH) secreting cells in the embryonic/larval as well as adult pituitary gland of the common Indian toad, Bufo melanostictus, have been studied by using antisera raised in rabbit against mammalian hypophysial hormones. Immunoreactive MSH and ACTH cells appear first in the dorsocaudal and rostral regions of the pituitary anlage (PA) at stage 21 (Gosner's classification) of the embryonic development. This is followed by the differentiation of TSH and PRL cells at stage 22 in the midventral and central regions of the PA respectively. Finally, at stage 23 the GTH cells appear in the rostral and the GH cells in the caudal regions of the PA. With the progress of the development, cells showing immunoreactivity to various antisera gradually increase in number, size, granular content and finally occupy the characteristic adult disposition. The MSH cells comprise the pars intermedia. In the pars distalis (PD) the ACTH cells are localized in the rostroventral region, TSH cells in the central region and the GH cells in the dorsocaudal region. However, GTH and PRL cells are distributed throughout the PD.