Hormonal Regulation of Kidney Function

Question 0

Angiotensin II

Answer 0

Formed by the cleaving of Angiotensin I by ACE; promotes Na+ and H2O reabsorption by:

      1. Direct reabsorption in the PT
      2. Indirectly stimulating aldosterone secretion
      3. Stimulating ADH secretion

*Also promotes vasoconstriction on vascular smooth muscle

Question 1

Renin

Answer 1

Activates angiotensinogen

*Secreted by juxtaglomerular cells in response to decreased blood pressure or ECV or via decreased NaCl delivery to the macula densa; inhibited by angiotensin II (negative feedback)

Question 2

Prostaglandins

Answer 2

Mainly synthesized in the medulla and collecting tubules; synthesis increased by vasoconstrictors; primary prostaglandin is PGE2

• Will inhibit the fnxn of ADH
• Induces local vasoDILATION to minimize renal ischemia
• NSAIDs can lead to irreversible renal ischemia in hypovolemic disorders

Question 3

Bradykinin

Answer 3

Produced by renal cells and in the plasma from kallikrein; acts as a vasodilator that promotes natiuresis and diuresis

Question 4

ADH

Answer 4

Formed in the supraoptic and paraventricular nuclei of the hypothalamus, ADH will stimulate V2 receptors on the basolateral membrane of principal cells to increased luminal aquaporins (AQP2); also stimulates V1 receptors in systemic vasculature to cause phosphatidylinositol turnover and vasoconstriction (Increase BP)

*Released in response to increased Posm and depletion of PV

Question 5

Diabetes Insipidus

Answer 5

Central: Decreased secretion of ADH occurring after head trauma; corrected by infusion of ADH

Nephrogenic: Resistance to ADH action in the kidney; decreased expression of AQP2

*Both are characterized by intense thirst and polyuria

Question 6

CBG-A

Answer 6

Cortisol Binding Globulin; binds aldosterone in the circulation

*Can also be bound to albumin

Question 7

Mineralcorticoid Escape

Answer 7

Prolonged treatment w/ aldosterone causes salt retention until escape occurs due to rise in ECF volume

*Decreases Na+ reabsorption

Question 8

Calcitriol

Answer 8

Hydroxylated Vitamin D3 in the PT that:
Increases intestinal absorption of Ca2+ and PO43-
Decreases PTH secretion
Increases bone resorption
Increases Ca2+ reabsorption

*Release stimulated by PTH or Hypophosphatemia

Question 9

EPO

Answer 9

Produced in the peritubular capillary endothelial cells, this glycoprotein acts on precursor cells to increase RBC production

*Released during decreased O2 delivery to the kidney