ADH- increase permeability to urea.

i dont undestand why ADH increases the permeability to urea in the collecting duct?

it increases permeability to water, so that more diffuses back into the body. therefore creating a more concentrated urine.

Reply 2

Comp_Genius

Presumably you are asking how ADH increases the permeability of the collecting duct cells to urea. The reason is that ADH via a cyclic AMP mechanism, results in the insertion of VRUT (Vasopressin-regulated urea transporter) into the luminal membrane.

Reply 3

w8wizz

darkenergy

i dont have a clue what that means. the book says that is makes the water potential even more negative and so more water diffuses back into the blood by osmosis.

Reply 4

Comp_Genius

Well the ADH makes the collecting duct more permeable to urea, so there is an increased 'drive' for water to leave the cell i.e. water potential is more negative compared to the interior of collecting duct. So more water is drawn out of the collecting duct, and eventually back to the blood by osmosis.