Postnatal decline in gonadal secretion of dehydroepiandrosterone and 3 beta-hydroxyandrosta-5,7-dien-17-one in the newborn foal.

This research studies the significant decrease in gonadal secretion of dehydroepiandrosterone (DHEA) and 3 beta-hydroxyandrosta-5,7-dien-17-one (also known as 7-dehydro-DHEA) in newborn foals. The decline happens just days after birth, and the implications of this decline are yet to be fully understood.

Research Objectives

• The study aimed to investigate levels of DHEA and 7-dehydro-DHEA in newborn foals within the first days post-birth. This stems from the observation that these precursor steroids are secreted in large quantities by the fetus but decline in late pregnancy.
• The research also aimed to determine which steroid was predominantly produced by the foal’s gonads at birth.

Methods and Approach

• The researchers used a direct radioimmunoassay (RIA) with a DHEA antibody which cross-reacts with 7-dehydro DHEA for the initial measurements.
• The team then used solid-phase extraction, followed by the separation of unconjugated from conjugated steroids. This was followed by high-performance liquid chromatography (HPLC) fractionation to confirm the initial findings.
• This study compared the detection on HPLC at wavelengths of 254 and 280 nm with results obtained from RIA to ensure accuracy.

Findings

• The researchers found that DHEA is the major steroid produced by the gonads at birth. The concentrations of these steroids were highly variable within the first day of postnatal life but saw a rapid decline within 96 hours after birth.
• The study also noted an increase in the ratio of DHEAS/DHEA as the value for total DHEA falls, indicating the presence of a sulphate form of DHEA post-birth.
• Despite these observations, the mechanism driving this sharp decline in gonadal steroidogenesis remains unknown, as does its possible significance to the newborn foal’s health and development.