ACTH-elicited sodium appetite in sheep

Area of Science:

• Endocrinology
• Animal Physiology
• Neuroscience

Background:

• Adrenocorticotropic hormone (ACTH) plays a crucial role in regulating adrenal gland function.
• Sodium (Na) appetite is essential for maintaining electrolyte and fluid homeostasis.
• Previous research suggests a link between ACTH and mineral intake, but the precise mechanisms are not fully understood.

Purpose of the Study:

• To investigate the effect of ACTH on sodium appetite in sheep.
• To determine if the observed sodium appetite is specific to sodium chloride (NaCl).
• To elucidate the role of adrenal steroid hormones in mediating ACTH-induced sodium appetite.

Main Methods:

• Sheep were administered intramuscular injections of synthetic ACTH (45 U twice daily for 5 days).
• Sodium chloride (NaCl), potassium chloride (KCl), and calcium chloride (CaCl2) intake were measured.
• Experiments were conducted in both normal and adrenalectomized sheep, with hormone infusions in the latter.

Main Results:

• ACTH treatment significantly increased NaCl intake in sheep, reaching approximately 50% of their total extracellular fluid sodium.
• The enhanced appetite was specific for NaCl, as KCl and CaCl2 intake remained unchanged.
• ACTH-induced sodium appetite was dependent on adrenal function, as it was ineffective in adrenalectomized sheep but could be mimicked by adrenal steroid hormone infusion.

Conclusions:

• Adrenocorticotropic hormone (ACTH) induces a specific appetite for sodium chloride in sheep.
• This effect is dependent on the adrenal cortex and mediated by adrenal steroid hormones.
• ACTH acts via adrenal steroids to regulate sodium appetite and maintain mineral homeostasis.