Corticotropin-releasing hormone and epidermal growth factor: mitogens for anterior pituitary corticotropes.

Anterior pituitary corticotropes increase in number after stimulation by adrenalectomy or corticotropin-releasing hormone (CRH). However, is this brought about by mitoses? Furthermore, as epidermal growth factor (EGF) is a potent secretagogue for corticotropes, is it also a mitogen? To address these questions, populations of corticotropes enriched to 88-97% by counterflow centrifugation were studied after growth in 0-10 nM CRH with and without 0.1-10 ng/ml EGF.

Cells that express luteinizing hormone (LH) and follicle-stimulating hormone (FSH) beta-subunit messenger ribonucleic acids during the estrous cycle: the major contributors contain LH beta, FSH beta, and/or growth hormone.

There is a 2-fold increase in the percentage of gonadotropes bearing LH beta or FSH beta mRNAs or antigens as the cells approach proestrus. The purpose of this study was to identify the source of these cells with dual labeling techniques. The first hypothesis was that they stemmed from small monohormonal gonadotropes (containing only LH or FSH) that were driven to transcribe and translate the other gonadotropin.

Heightened secretion by small and medium-sized luteinizing hormone (LH) gonadotropes late in the cycle suggests contributions to the LH surge or possible paracrine interactions.

LH secretion from pituitary cell fractions separated by centrifugal elutriation was compared to learn whether any contributed to the LH surge. After plating (1 h) and stimulation with 0-10 nM [D-Lys6]GnRH (4 h), some fractions secreted levels that were out of proportion to their enrichment. Large cells from proestrous morning rats (3-fold enriched) secreted 4.

Epidermal growth factor enhances ACTH secretion and expression of POMC mRNA by corticotropes in mixed and enriched cultures.

Previous studies have shown that epidermal growth factor (EGF) stimulates the release of adrenocorticotropin (ACTH) in vivo and in vitro by amplifying the effects of corticotropen-releasing hormone (CRH). The aim of the present studies was to compare responses to EGF by corticotropes in an unseparated culture with those in cultures enriched to 90-93% ACTH-beta-endorphin cells (by counterflow centrifugation). Since EGF binding sites had been identified on growth hormone (GH) or prolactin (PRL) cells (9), the enriched corticotrope cultures were studied to learn if the abundant GH or PRL cells found in unseparated cultures were required to mediate the actions of EGF.

Cytochemical studies of responses of corticotropes and thyrotropes to cold and novel environment stress.

Cold stress stimulates the release of both ACTH and TSH from the pituitary. More striking changes in ACTH content have been seen in the intermediate lobe after cold stress. Therefore, this study was designed to test responses of individual anterior lobe corticotropes to cold exposure.