Absence of renal action of pure intermediate lobe hormone

Area of Science:

• Endocrinology
• Renal Physiology

Background:

• The intermediate lobe of the pituitary gland produces melanophore-stimulating hormone (MSH).
• MSH's role in regulating water and electrolyte balance is not fully understood.

Purpose of the Study:

• To investigate the effects of MSH on urinary excretion of water, sodium, potassium, and chloride in conscious dogs.
• To determine if MSH influences the renal actions of vasopressin or oxytocin.

Main Methods:

• Studies were conducted in conscious dogs during both water diuresis and a non-diuretic state.
• Various doses of MSH were administered to assess renal function.
• The interaction of MSH with vasopressin and oxytocin was examined.

Main Results:

• MSH, in doses up to 2.3 IU, did not alter renal function or the excretion of water, Na, K, and Cl.
• MSH did not modify the renal effects of administered vasopressin or oxytocin.
• A significant antidiuretic effect observed with a high MSH dose was attributed to vasopressin contamination.

Conclusions:

• MSH does not appear to have a direct role in regulating water and electrolyte excretion in dogs.
• The antidiuretic properties previously associated with MSH may be due to vasopressin contamination in experimental preparations.