The mitogenic effects of corticotrophin-releasing factor on the anterior pituitary gland of the rat

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Abstract
The immunohistochemically defined corticotroph population in the anterior pituitary gland of the adult male Sprague–Dawley rat has been quantified at 2 and 6 weeks after bilateral adrenalectomy using the stereological measurement, volume density (Vv). An approximately twofold increase in corticotroph Vv was demonstrated at 2 weeks in adrenalectomized rats compared with that in sham-operated controls and this was maintained at 6 weeks. Daily i.p. injections of ovine corticotrophin-releasing factor (CRF-41) induced a significant dose-related increase in corticotroph Vv when administered at doses of 25 and 50 μg/kg body weight, but this was less than the increase following adrenalectomy. Assessment of changes in mitotic activity of the total anterior lobe of adult Sprague–Dawley rats and of the corticotroph population was also made after daily i.p. injections of 50 μg CRF-41/kg for 2 and 7 days. There was no increase in overall mitotic index at either time. However, the numbers of mitotic corticotrophs were significantly increased in CRF-injected animals compared with those in saline-injected rats. These results indicate a role for CRF-41 in the regulation of corticotroph growth. J. Endocr. (1988) 118, 237–241