RENAL PHYSIOLOGY-ANTIDIURETIC HORMONE

SUMMARY

1. ADH - neurohypophysial hormone that acts on the late distal tubule and cortical collecting duct to increase water permeability (hence water resorption) and mediate the urine concentration.

2. ADH levels are regulated by (1) Osmoreceptors in the hypothalamus (2) Volume (stretch) receptors in the left atrium and blood vessels.

3. The strongest stimulant for ADH release is significant volume loss resulting in hypotension; e.g., hemorrhage. This stimulates both the stretch receptors and baroreceptors.

4. High plasma osmolality is a weaker but more sensitive stimulus for ADH release.

5. ADH calls forth an aquaporin protein (AQP-2) from the cytoplasm, several of these gather at the cell membrane and make a water channel.

Reference(s)

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