Steroidogenesis in isolated adrenocortical cells during development in rats

Area of Science:

• Endocrinology
• Developmental Biology
• Cellular Physiology

Background:

• The hypothalamo-pituitary-adrenal axis in neonatal rats exhibits diminished responsiveness to stimuli postnatally.
• Understanding adrenal cell function during early development is crucial for comprehending stress response maturation.

Purpose of the Study:

• To quantify the developmental changes in adrenocortical cell responsiveness to adrenocorticotropic hormone (ACTH).
• To pinpoint intracellular locations of adrenal cell hyporesponsiveness in neonatal rats.

Main Methods:

• Collagenase-dispersed adrenocortical cells from neonatal (d1, d10) and adult rats were used.
• Cells were stimulated with ACTH, dibutyryl cAMP ((Bu)2cAMP), and 20 alpha-Hydroxycholesterol (20 alpha-OHCHOL) to assess steroidogenic responses.

Main Results:

• Steroidogenic responses to ACTH and (Bu)2cAMP were significantly lower in neonatal cells (d1, d10) compared to adult cells, with d10 showing the least response.
• Responsiveness to (Bu)2cAMP mirrored ACTH response, indicating a limitation distal to cAMP formation.
• 20 alpha-OHCHOL did not normalize responses, suggesting a blockade beyond cholesterol transport, potentially involving cytochrome P450 enzymes.
• Basal corticosterone secretion was higher in neonatal cells, despite lower stimulated secretion.

Conclusions:

• Neonatal rat adrenal hyporesponsiveness to ACTH is located downstream of cAMP signaling and cholesterol transport.
• Differential cytochrome P450 enzyme activity or expression is a likely contributor to impaired steroidogenesis in neonatal adrenal cells.
• Neonatal adrenal cells exhibit higher basal activity but a blunted response to stimulation compared to adult cells.