Select all of the FALSE statements about Anti-diuretic Hormone and Atrial Natriu

Question

Select all of the FALSE statements about Anti-diuretic Hormone and Atrial Natriuretic Peptide? There may be more than one answer. (2 pts)

Select one or more:

a. Anti-diuretic Hormone promotes the insertion of aquaporin 2, 3, and 4 channels at the membrane of the distal convoluted tubule and collecting duct which will promote water reabsorption.

b. When Atrial Natriuretic Peptide binds to the posterior pituitary gland, the posterior pituitary gland will decrease the ADH production and the result is a decrease in water reabsorption along the distal convoluted tubule and collecting duct

c. Anti-diuretic Hormone, which has a half-life of 18 minutes, increases the production and opening of Na+ channels at the proximal convoluted tubule.

d. Atrial Natriuretic Peptide causes a vasoconstriction of the afferent arteriole and a vasodilation of the efferent arteriole which increases the glomerular filtration rate at the glomerular capillary.

e. When the plasma osmolarity is lower than 2% of 0.3Osm, the amount of Anti-diuretic Hormone secretion decreases.

f. Atrial Natriuretic Peptide increases the urine flow rate and corrected urine specific gravity while Anti- diuretic Hormone decreases the urine flow rate and increases the corrected urine specific gravity.

g. All of the above

Explanation / Answer

Aquaporins 2.4 and 6 are present in the principal cells in the collecting duct of the kidneys. They function in vasopressin or anti diuretic hormone regulated water retention. Exit pathways for apically reabsorbed water occur though aquaporin 2. Water is collected by peritiubular capillaries and systemic circulation. Aquaporin 3 and 4 aids in water reabsorption through principal cells of collecting duct. Aquaporin 2 and 3 knockout mice suffer from polyuria.

When the plasma osmolarity is lower than 2% of 0.3OSm, the osmoreceptors are not activated. As a result, secretion of antidiuretic hormone is suppressed. When the osmolarity rises above the threshold level, the osmoreceptors are activated that stimulate hypothalamic neurons that secrete antidiuretic hormone. The threshold for stimulating ADH secretion in plasma is approximately 280 mOsm/kg (0.28Osm) while the threshold for stimulating thirst is approximately 290 mOsm/kg (0.29 Osm).

ADH has a half-life of 15-30 minutes. Further, it is aldosterone via its binding to mineralocorticoid receptor opens the sodium channel of the proximal convoluted tubules.

Atrial natriuretic hormone is a cardiac hormone functioning to lower blood pressure and controls electrolyte balance. ANP inhibit ADH secretion by directly binding to the pituitary. This effect is partly due to increase in CGMP: cAMP ratio.

ANP acts on the kidneys by vasodilating the glomerular afferent arterioles and vasocontricting the efferent arterioles. This increases the pressure of the glomerular capillaries increasing the glomerular filtration rate. This leads to increased filtration of sodium and water, increasing urine flow. ADH release causes increased tubular water re-absorption. Hence, there is a decrease urine volume and increase in specific urine gravity.

Hence, c, d and g are incorrect statements.

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