Bioassay of ACTH (Adrenocorticotropic Hormone)

• Bioassay of ACTH Measures adrenal cortex stimulation in test animals.
• Bioassay of ACTH Evaluates steroid hormone release as an ACTH response indicator.

Principle

• ACTH stimulates the adrenal cortex to secrete corticosteroids (cortisol in humans).
• Bioassay measures either adrenal gland weight, plasma corticosteroid levels, or specific physiological changes caused by elevated corticosteroids.

Methods

1.  Adrenal Ascorbic Acid Depletion Method (Older Method)

• Rationale: ACTH causes the adrenal glands to use up ascorbic acid when synthesizing steroids.
• Procedure:
  1. Treat groups of rats with varying doses of standard ACTH and test ACTH.
  2. After a specific time, sacrifice the animals and measure the remaining ascorbic acid in the adrenal glands.
• Potency Determination: Plot the depletion of ascorbic acid vs. dose for standard and test.

2. Plasma Corticosterone Method

• Procedure:
  1. Inject standard or test ACTH into rats.
  2. After a set period, measure plasma corticosterone levels.
• Potency Determination: Compare the corticosterone response to standard vs. test across a range of doses.

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