Developmental changes in pulmonary and renal angiotensin-converting enzyme concentration in fetal and neonatal horses.

The research article explores the changes in angiotensin-converting enzyme (ACE) concentration in the lungs and kidneys of horses before and after birth. It was found that the amount of ACE in the lungs increased towards the end of pregnancy, while ACE in the kidneys remained steady throughout the gestation period and after birth.

Study Purpose and Methodology

• The purpose of this study was to investigate the developmental changes in pulmonary and renal angiotensin-converting enzyme (ACE) concentrations in fetal and neonatal horses.
• ACE is a crucial enzyme involved in regulating blood pressure and maintaining body fluid balance both before and after birth.
• The researchers measured and compared ACE concentrations in the lungs and kidneys of horses during the various phases of gestation and postnatal life.

Key Findings

• Fetal pulmonary ACE concentration steadily increased from 250 days and reached a peak close to term (around 335 days).
• Newborn foals had significantly higher concentrations of ACE in their lungs compared to fetuses in late gestation and animals aged between 1 day and 2 weeks postnatal.
• Renal (kidney) ACE was found in fetal horses from as early as 100 days of gestation, but the concentration showed no trend of increase or decrease during the second half of gestation or in the early postnatal period.
• ACE concentrations in fetal kidneys remained approximately 10 times lower than the average pulmonary values.

Interpretations and Implications

• The comparable steady concentration of renal ACE may be associated with the functional immaturity of the horse kidneys while the fetus is still in the womb.
• The surge in pulmonary ACE concentration towards the end of pregnancy in horses could be triggered by a surge of cortisol, a hormone that usually increases close to delivery.
• If a horse is born prematurely, this may interrupt the initiation of ACE production in its lungs and affect the normal maturation of the renin-angiotensin system (which regulates blood pressure and fluid balance).
• These findings may have important implications for understanding the developmental physiology of horses and the role of ACE in maintaining circulatory homeostasis.