0013-7227/85/1161-0439$02.00/0 Endocrinology Copyright © 1985 by The Endocrine Society Vol. 116, No. 1 Printed in U.S.A. Quantification of Morphological Changes in Pituitary Corticotropes Produced by in Vivo Corticotropin- Releasing Factor Stimulation and Adrenalectomy* K. N. WESTLUND, G. AGUILERA, AND G. V. CHILDSf Department of Anatomy, The University of Texas Medical Branch (K.N.W., G.V.C.), Galveston, Texas 77550; and the ERBB, National Institute of Child Health and Human Development, National Institutes of Health (G.A.), Bethesda, Maryland 20205 ABSTRACT. Physiological and morphological changes pro- duced by corticotropin-releasing factor (CRF) stimulation in vivo were studied in pituitaries immunocytochemically stained for ACTH. After 48-h ip minipump infusions of 10 or 50 ng/min CRF, serum ACTH levels were increased significantly over values in control groups that included both intact rats and rats exposed to sham abdominal surgery. Correlative morphological changes included a striking increase in corticotrope cell area. This was coupled with an apparent decrease in the percentage of stained cells, probably due to degranulation. The cellular responses were similar to those after adrenalectomy described previously by us and others. Therefore, in a parallel study, additional groups of rats were adrenalectomized and studied 24 and 48 h after the surgery. Even greater changes in serum ACTH, corticotrope cell area, and percentages were observed in the adrenalectomized rats. The difference between the CRF-infused and adrenalectomized groups was probably due to the lack of corticosterone feedback in the latter group. Among the control groups, there were no differences between intact rats and rats exposed to sham abdominal surgery. Rats subjected to sham adrenalectomy, however, showed corticotrope responses similar to those of CRF-infused rats, except that the cells were more densely stained. The present studies thus show dramatic changes in ACTH cell area, extent of staining, and percentages after in vivo CRF stimulation. In all of the experimental groups, an excellent correlation existed between serum ACTH levels and the degree of the morphological changes in the corticotropes. {Endocrinology 116: 439-445, 1985) M OST available evidence shows that corticotropin- releasing factor (CRF), as sequenced by Vale et al. (1, 2), is the major regulator of ACTH release. CRF has been detected by RIA in the median eminence (ME) (3, 4). Adrenalectomy causes a 2-fold increase in ME CRF levels (4) and an increase in immunoreactive stain for the polypeptide (5). Immunocytochemical studies in the rat have shown that CRF terminals are localized within the external zone of the ME in the vicinity of the capillary loops (5- 9) and the internal region of the pituitary stalk (10). CRF then appears to have a mode of entry similar to that of other known releasing factors. CRF-immunoreac- tive cells have also been localized in the hypothalamus of colchicine-treated rats in the paraventricular, periven- tricular, anterior, and other hypothalamic nuclei (6, 8- 12). Received July 3,1984. Address requests for reprints to: K. N. Westlund, Ph.D. or G. V. Childs, Ph.D., Department of Anatomy, The University of Texas Medical Branch, Galveston, Texas 77550. * This work was supported in part by NIH Grants NS-0739 and HD-00395 and seed funds from The University of Texas Medical Branch. t Formerly G. C. Moriarty. Synthetic CRF is a potent stimulator of ACTH release both in vivo and in vitro (1, 13-18). In addition, specific high affinity binding sites for CRF have been found in pituitary cell membrane suspensions (19, 20). Target cells for CRF are the stellate corticotropes in intact rats or their counterparts in adrenalectomized rats (adrenal- ectomy cells) that were described by Siperstein and Miller in 1970 (21). In early immunohistochemical stud- ies, the chemical identity of this cell type was confirmed (22). More recently, these cells were shown by autora- diography to bind [ 125 I]CRF (23). Our cytochemical studies of corticotropes were ex- panded recently to confirm the chemical identity of the CRF target cells. In a recent report, a biotin-labeled CRF analog was localized on cultured pituitary cells that were simultaneously stained for ACTH with immunocyto- chemical and affinity cytochemical staining techniques (24). The potent biotin-labeled CRF bound to all corti- cotropes in the dispersed pituitary monolayer culture. The binding was dose dependent and produced ACTH release equipotent with that caused by unlabeled syn- thetic CRF. No other cell types bound CRF. The effect of adrenalectomy on corticotrope morphol- ogy is well known (21, 22, 25, 26). The cells expand in 439 The Endocrine Society. Downloaded from press.endocrine.org by [Gwen Childs] on 23 August 2014. at 13:42 For personal use only. No other uses without permission. . All rights reserved.