Immunohistochemical localisation of steroidogenic enzymes and phenylethanolamine-N-methyl-transferase (PNMT) in the adrenal gland of the fetal and newborn foal.

The research paper studies the localisation and changes in distribution of key enzymes associated with cortisol production in the adrenal gland of fetal and newborn horses. The researchers determined that there is an increase in fetal adrenal cortisol output close to the time of birth, and these findings are correlated with the increase of cortisol-dependent enzymes.

Approach and Sample Selection

• The researchers used immunohistochemistry to identify the location and changes in the distribution of main enzymes linked with cortisol production such as P450scc, P450C17, and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in the adrenal tissue from fetal and newborn horses.
• The samples consisted of adrenal tissue from fetuses at Day 100-156 (n = 5), Day 244-295 (n = 8), greater than Day 300 (n = 4), and from newborn foals (n = 6). All samples were studied using specific antibodies and the avidin-biotin-peroxidase technique.

Findings on Steroidogenic Enzymes

• The research found that all three steroidogenic enzymes were present by Day 150, but present in less than 20% of the cortical cells in the adrenal.
• By late gestation, the distributions of these enzymes varied, with them appearing in approximately 30% of the cells. P450SCC and P450C17 were most common in cortical cells close to the medulla, whereas 3 beta HSD was distributed throughout the cortex but more in the zona fasciculata.
• Following birth, there was a substantial increase in IR-3 beta HSD and IR-P450SCC throughout the adrenal cortex, while IR-P450C17 was present in most cells of the zonae fasciculata and reticularis.

Findings on Cortisol-Dependent Enzyme

• Cortisol-dependent enzyme, phenylethanolamine-N-methyl-transferase (PNMT), was localised to the nuclei of scattered medullary cells at the medullary-cortical interface by Day 150.

Conclusion

• The increase in adrenal cortisol output and the rise of cortisol-dependent enzymes close to the time of birth indicate a crucial link in enzymatic activity and cortisol-related birth processes, thus contributing to our understanding of parturition in horses.