Effects of centrally applied somatostatin on pituitary adrenocorticotropes in female rats.
Effects of intracerebroventricular (i.c.v.) application of somatostatin (SRIH-14 or SRIH-28) on growth and function of pituitary adrenocorticotropes (ACTH cells) were examined in adult female Wistar rats. Animals were subjected to i.c.v. administration of three 1-microg doses of SRIH-14 or SRIH-28 dissolved in 5 microl saline every second day. Controls were treated in the same way with the same volume of saline only. ACTH-producing cells were studied using the peroxidase-antiperoxidase (PAP) immunohistochemical procedure; blood samples were collected for hormone analyses 5 days after the last injection. SRIH-28 treatment decreased (p < 0.05) all morphometric parameters compared to control rats. Volume of ACTH cells decreased by 10%, nuclei by 36% and volume density by 13%. No significant changes (p > 0.05) in these parameters occurred after SRIH-14 treatment. Plasma concentration of ACTH in SRIH-28-treated rats was significantly lower (p < 0.05) than in control rats by 35%. In SRIH-14-treated rats, plasma concentration of ACTH was slightly, but not significantly (p > 0.05) increased by 13% compared to saline treatment. These observations suggest that centrally administered somatostatin-28, but not somatostatin-14, is specifically involved in the control of growth and secretory activity of ACTH cells in female rats. Thus, selective pharmacological manipulation of SRIH-28 receptors reached from CSF may affect ACTH activity without altering actions usually attributed to receptors sensitive to SRIF-14.
Starcević
V
V
Institute of Physiology, School of Medicine, University of Belgrade, Belgrade, Yugoslavia.
Milosević
V
V
Brkić
B
B
Severs
W B
WB
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000187:drug effects*; D000818:Animals; D005260:Female; D006728:Hormones / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000494:pharmacology*
D006728:Hormones; D013004:Somatostatin; D000324:Adrenocorticotropic Hormone