renal 6

Question 1

define secretion in terms of net movement of a solute

Answer 1

• movement of solute from blood into lumen of nephron

Question 2

Why do organic acids competitively inhibit secretion of other organic acids?

Answer 2

• organic acids utilize a common carrier protein and can experience competitive inhibition

Question 3

why do all organic bases competitive inhibit secretion of all other organic bases

Answer 3

• organic bases also use a common carrier proteins and can experience competitive inhibition

Question 4

What are the effects of low urine pH on the net secretion, excretion and plasma concentration of organic acids (e.g. aspirin)

Answer 4

• organic acids binds to the H+ in acidic urine
• the ASA-H compound more easily traverses the membrane and thus goes back into the blood
• decreases net secretion, excretion and increases plasma concentration of organic acids

Question 5

Why does alkalinizing the urine (ingesting bicarbonate) would be helpful in treating an aspirin overdoes

Answer 5

• ## there would be low H+ floating in the urine and the ACA (aspirin) won’t be able to bind it and make a compound 00> thus it can’t go back across the membrane to leave the lumen

Question 6

why is the clearance of PAH a measure of the effective renal plasma flow (ERPF)

Answer 6

• PAH is removed from the plasma that enters the afferent arteriole, so PAH is a measure of volume of plasma that entered the kidney per unit time.

Question 7

Calculate the ERPF when given the plasma and urinary concentrations of PAH and the rate of urine production

Answer 7

• Similar to inulin clearance

- Cpah = Upah * V/Ppah

Question 8

Calculate the filtartion fraction when given GFR and ERPF

Answer 8

• is the fraction or percent of plasma delivered to kidneys that is filtered
• FF = GFR/ERPF

Question 9

describe why the nephron segments upsteam of the distal tubule do not contribute to the regulation of potassium balance

Answer 9

• 90% of filtered K is reabsorbed by the end of the thick ascending loop of henle
• this occurs whether the body is in a state of normal K, hypo or hyperkalemia
• the distal tubule dictates whether or not the remaining 10% is reabsorbed or a certian amount is secreted –> depends on whether or not the body needs or wants to get rid of K

Question 10

describe the effect of hyperkalemia on aldosterone secretion

Answer 10

• High K causes RELEASE of aldosterone from adrenal cortex
• aldosterone stimulates the Na/K pump on the BASOLATERAL membrane of tubular cell
• RESULTS IN K BEING PUMPED into the cell and thus the lumen of the nephron

Question 11

describe the other effects of Aldosterone on collecting ducts

Answer 11

• aldosterone activates ENaC pumps in collecting ducts which reabsorb Na and secrete K.
• -> ENaC can be INHIBITED by ANP (and Na is excreted more)

Question 12

what are the effects of increased aldosterone and increased potassiumon reabsorption or section of potassium

Answer 12

• increased aldosterone means activated Na/K pumps and more secretion/excretion of K

Question 13

how do diuretics causes depletion of body potassium

Answer 13

• loop diuretics block Na/K pumps in thick ascending limb of LOH
• -> this increases flow through late distal tubule and collecting ducts and cause K secretion to increase
• Aldosterone blockers have opposite effect and spare K INCREASE SERUME K

Question 14

what are the effects of alkalosis on potassium

Answer 14

• Alkalosis stimulates Na/K ATPase on late distal conoluted tubule and collecting ducts
• -> increases flow of K into cells and then lumen
• Alkalosis also INCREASES permeability to apical (lumen) membrane to Potassium so it flows into the lumen faster
• -> alkalosis increases secretion and excretion and thus HYPOKALEMIA