Renal Physiology

Secretion

• Selective process of transferringmolecules from the extracellular fluid intothe lumen.

• K+ regulation by Aldosterone in the distaltubule.

• Aldosterone is synthesized in the adrenalcortex and released when there areincreased levels of K+.

Secretion II

• Through translation of protein channelsand modifier proteins, K+ is secreted intothe lumen of the distal tubule.

• Remember the Na+-K+-ATPase on thebasolateral membrane??

• Well, Na+ reabsorption is necessary forthis mechanism.

Vasopressin/ADH

• Vasopressin is released by the posteriorpituitary and aids in water retention.

• Controls urine concentration in thecollecting duct by reabsorbing water.

• ADH bind to it’s receptor and through acAMP signal, Aquaporin-2 water pores aremoved to the apical membrane.

• Water is recovered.

Effects of Alcohol

• Alcohol inhibits ADH secretion.• Water recovery is significantly diminished

and urine volume increases.