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Developmental changes in ovine corticotrophs in vitro
F M Perez1, J Schwartz, J C Rose
1Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27157, USA. fperez@bgsm.edu
Endocrinology
|March 1, 1997
Summary
Fetal sheep corticotrophs shift their response from CRH to AVP during development. This involves changes in the number of ACTH-secreting cells and the amount of hormone released per cell.
Area of Science:
- Endocrinology
- Developmental Biology
- Reproductive Physiology
Background:
- Fetal sheep corticotrophs (adrenocorticotropic hormone-producing cells) exhibit developmental changes in their responsiveness to corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP).
- Previous studies indicated a shift in responsiveness from CRH to AVP during late gestation and into adulthood.
Purpose of the Study:
- To investigate the maturational changes in ovine fetal corticotrophs.
- To characterize the developmental alterations in ACTH secretion in response to CRH and AVP.
Main Methods:
- Immunocytochemistry to determine corticotroph frequency.
- Radioimmunoassay (RIA) to measure ACTH secretion from cell populations.
- Cell immunoblotting to analyze individual corticotroph responses to CRH and AVP at different gestational ages (100, 120, 135 days) and in adults.
Main Results:
- Corticotroph frequency decreased significantly from 22% in early gestation to 9% in adults.
- Responsiveness to CRH diminished, while responsiveness to AVP increased with advancing gestation.
- Early in gestation (100 days), CRH increased the proportion of secreting cells, with negligible AVP effect. By late gestation (135 days) and adulthood, AVP significantly increased the proportion of secreting cells, with CRH having a minimal effect.
- The average amount of ACTH secreted per cell did not change with CRH or AVP stimulation in early gestation but increased near term and in adults.
Conclusions:
- Ovine fetal corticotrophs undergo significant maturational changes in their response to CRH and AVP.
- These changes involve alterations in both the number of responsive cells and the quantity of ACTH secreted per cell.
- The developmental shift dictates whether the secretory response is mediated by an increase in secreting cell proportion or an increase in hormone release per cell.