Sympathoadrenal and other responses to hypoglycaemia in the young foal.

The research paper investigates how insulin-induced low blood sugar (hypoglycaemia) affects the plasma catecholamines, cortisol, and metabolites in newborn foals and 7-14 day old foals, with a focus on adrenal responses. It found that younger foals have a slower and less severe glucose drop, and a weaker adrenocortical response. However, as they age, these responses become heightened, showing an increased reaction to hypoglycaemia.

Investigating Hypoglycaemia in Foals

• The researchers examined the impact of insulin-induced hypoglycaemia in new-born foals and those between 7 to 14 days old, focusing particularly on the changes observed in plasma catecholamines, cortisol, and metabolites.
• They found that a higher insulin dose given to newborns resulted in a slower and less severe drop in plasma glucose compared to a lower dose administered to the older foals.
• Additionally, the level of adrenaline (but not noradrenaline) in the plasma showed an inverse relationship with the concentrations of glucose when glucose levels dropped below 2 mmol/l.
• The research also showed that the older foals exhibited a more pronounced adrenergic response to low blood sugar, compared to the newborns.

Hypoglycaemia after fasting and Adrenocortical Response

• The study found no significant changes in glucose or catecholamines levels after the foals were fasted.
• The adrenal cortex response to hypoglycaemia was weak immediately after birth. Still, it became more significant in older foals, shown by a threefold increment in plasma cortisol approximately 60 minutes after gel insulin administration.

Metabolic Changes due to Hypoglycaemia

• The study observed significant increases in plasma Free Fatty Acids (FFA) after low blood sugar in both groups of animals, though it was less noticeable in the newborns.
• There was also a significant correlation between adrenaline and FFA values in the plasma. Hypoglycaemia further resulted in an increase in plasma lactate and a gradual decrement in alpha-amino nitrogen.

Conclusions

• Overall, the findings reveal that low blood sugar in foals leads to stimulation of both adrenal system components -sympathetic medullary and cortex- resulting in several metabolic changes.
• It was also observed that the response to the hypoglycaemic effects of insulin was stronger and faster in older foals than in the newborns, suggesting the latter demonstrate some degree of insulin resistance.