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This Article Full Text Full Text (PDF) All Versions of this Article: 296/2/E300    most recent 90775.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Carey, L. C. Articles by Rose, J. C. Search for Related Content PubMed PubMed Citation Articles by Carey, L. C. Articles by Rose, J. C.

Cortisol infusion in late-gestation hypothalamo-pituitary disconnected sheep fetus restores pituitary cell responsiveness to arginine vasopressin

Departments of ¹Obstetrics/Gynecology, ³Neurosurgery, and ⁴Physiology/Pharmacology and ²Center for Research in Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina

Submitted 11 September 2008 ; accepted in final form 22 November 2008

Corticotrophs in the fetal sheep become increasingly responsive to arginine vasopressin (AVP) in late gestation. We previously reported that this may be due in part to corresponding increases in signal transduction (inositol 1,4,5-trisphosphate, IP₃). These ontogenic changes are prevented by hypothalamo-pituitary disconnection (HPD), which also prevents fetal plasma cortisol concentrations from increasing in late gestation. This led us to hypothesize that cortisol is involved in mediating the changes in pituitary responsiveness. HPD was performed on fetal sheep at 120 days gestational age (dGA). Half of the HPD fetuses were infused with cortisol for 3 days beginning at 135–137 dGA (HPD+C). The remaining HPD fetuses and a group of sham-operated control fetuses were infused with saline. Pituitary cells were isolated and cultured. After 48 h, a subset of cells was stimulated with 100 nM AVP for 2 h, and the medium was collected for ACTH analysis. Another subset of cells was stimulated with 100 nM AVP for 30 min, and the formation of IP₃ was determined. Plasma cortisol concentrations increased rapidly within the first 6 h after infusion (5.2 ± 1.9 to 29.7 ± 4.9 ng/ml) but did not increase thereafter. Cells from HPD+C and sham-operated fetuses secreted significantly more ACTH than those from HPD fetuses (% increase from control: 33.0 ± 8.8%, 47.9 ± 10.6%, and 11.9 ± 2.4%, respectively). IP₃ formation was significantly increased in cells from HPD+C and sham-operated compared with HPD fetuses (% increase from control: 17.7 ± 4.4%, 18.9 ± 4.3%, and 4.6 ± 1.5%, respectively). These findings support the idea that cortisol plays a role in mediating the increase in pituitary responsiveness to AVP in the late-gestation fetal sheep.

inositol 1,4,5-trisphosphate; ovine fetus; cortisol replacement; adrenocorticotropic hormone