Chapter 28 Renal Tubular Reabsorption and Secretion Flashcards
Which of the following is correct regarding sodium glucose (SGLT) co-transporters and glucose transporters (GLUT)?
A. SGLTs are located on the basemement membrane, along with GLUTs, of the distal tubules. .
B. Both SGLTs and GLUTs are considered to be active transporters and use ATPases to move the sodium and glucose in opposite directions.
C. The SGLT is a form of secondary active transport, as the sodium and glucose are moved in the same direction, into the tubular cell, and eventually reabsorbed into the peritubular capillaries.
D. GLUTs are considered to be secondary active transport and uptakes 2 glucose at time.
C.
SGLT are located on the brush border (apical/luminal membrane) of the proximal tubules. Glucose transporters are located on the basolateral membrane of the proximal tubules. The S1 segement, or initial portion of the proximal tubule, house the SGLT2 and GLUT2. The S3 or distal portion of the proximal tubule house SGLT1 and GLUT1. SGLTs are considered to be secondary active transport, as two molecules, interact with the same carrier protein, and move in the same direction. GLUTs are considered to be passive facilitated diffusion, as the move of glucose on the basolateral membrane is done through bulk flow.
In the first half of this portion of the renal tubule, sodium has co-transporters with amino acids, glucose and other solutes. In the second half of this portion of the renal tubule, sodium is co-transported with chloride. Along this portion of the tubule, H+, organic acids and bases are secreted into the urine.
A. Thick ascending loop of Henle
B. Thin descending loop Henle
C. Proximal tubule
D. Cortical collecting tubule
C. Proximal tubule
This portion of the tubule contains a luminal 1Na/2Cl/1K pump, a luminal Na/H counter-transporter, and paracellular reabsorption of many cations (Mg++, Ca++, Na+ and K+).
A. Early distal collecting duct
B. Thin descending loop of Henle
C. Proximal tubule
D. Thick ascending loop of Henle
D. Thick ascending loop of Henle.
The thin descending loop of Henle is used mostly for reabsorption of water.
Which of the following is correct when distinguishing between the early and late distal tubule?
A. The early tubule is largely responsible for acid/base regulation in the kidney.
B. The late distal tubule has two types of cells, principal cells and intercalated cells.
C. The principal cells are used largely for sodium/chloride reabsorption
D. The intercalated cells are the target for potassium sparing diuretics.
E. The late distal tubule is impermeable to water, even when ADH is present in high amounts.
B. The late distal tubule has two types of cells, principal cells and intercalated cells.
The early distal tubule is primarily for Na and Cl reabsorption. The macula densa is located here and is responsible for regulating GFR and RBF. The late distal tubule is known as the diluting segment.
The diluting segment has two types of cells present. The principal cells and the intercalated cells (Type A and B). The principal cells are the site for potassium secretion and sodium reabsorption. Thus, these cells are the target for potassium sparing diuretics.
The intercalated cells are essentially opposites of each other. Type A is responsible for secretion of H+ and absorption of K+ and HCO3-. This is achieved through luminal H+/K+ countertransporters, H+ATPases and basolateral HCO3-/Cl- countertransporters. Type B has the same transporters, but on the opposing cell surfaces.
The late distal tubule is imperpeable to water unless vasopressin (ADH) is present.
What part of the tubule does this describe? ADH works on the cells to allow for further concentrating of the urine. The cells are permeable to urea, allowing for reabsorption to increase the osmolality. Hydrogen is secreted against the concentration gradient.
A. Early distal tubule
B. Proximal tubule
C. Medullary collecting duct
D. Thin descending loop of Henle
C. Medullary collecting tubule. This portion of the tubule is the final site for processing urine.
Describe glomerulotubular balance.
Glomerulotubular balance is the ability of the tubules to increase their reabsorption rate as there is an increased tubular load. The percentage of GFR reabsorbed in the proximal tubule stays the same, and prevents the overloading of the distal tubule.
When considering the net reabsorptive force across the peritubular capillaries, which of the following FAVOR reabsorption?
A. Hydrostatic pressure of the peritubular capillary
B. Hydrostatic pressure of the renal interstitium
C. Osmotic pressure of the peritubular capillary
D. Osmotic pressure of the renal interstitium
B and C. Hydrostatic pressure of the renal interstitium and osmotic pull of the peritublar capillary plasma proteins favor reaborption.
The other two OPPOSE filtration.
Which of the following correctly increases reabsorption rate into the peritubular capillaries?
A. Increased GFR
B. Decreased systemic plasma colloid osmotic pressure
C. Increased arterial pressure
D. Lowered resistance of efferent arteriole
A. Increased GFR
*** INCREASED peritubular colloid osmotic pressure -OR- DECREASED peritubular hydrostatic pressure means INCREASE in reabsorption rate ***
Peritubular capillary colloid osmotic pressure is proportional to systemic plasma colloid osmotic pressure and filtration fraction. Filtration fraction is the ratio of GFR/RBF. Therefore, either an increase of GFR or a decrease of RBF can cause an increase in filtration fraction. The increased filtration fraction means a larger portion of the blood has been filtered, increasing the plasma protein concentration and ultimately increasing the peritubular colloid osmotic pressure.
Regulation of the peritubular capillary hydrostatic and osmotic pressures are influenced by arterial pressure and resistance of afferent and efferent arterioles. Increases in arterial pressure raises peritubular capillary hydrostatic pressure and decreases reabsorption rate. Resistance of either afferent or efferent arteriole reduces peritubular capillary hydrostatic pressure and increases reabsorption rate.
Which of the following causes pressure natriuresis and pressure diuresis?
A. Increased angiotensin II
B. Decreased arterial pressure
C. Decreased GFR
D. Increase in renal interstitium hydrostatic pressure
D. Increased renal interstitial hydrostatic pressure causes a backleak of sodium into the tubular lumen, reducing net reabsorption of sodium and water. This can be due to increased arterial pressure, which increases peritubular capillary hydrostatic pressure, which in turn reduces reabsorption. Angiotensin II is responsible for sodium reabsorption by the tubules, both through itself and is stimulation of aldosterone. If these decrease, then sodium reabsorption is lessened.
Who am I?
I am formed in response to low blood pressure or hypovolemia. I constrict the efferent arteriole and this in turn lends toward a decrease in peritubular hydrostatic pressure, which ultimately increases net reabsorption. The constriction of the efferent arteriole also increases peritubular colloid osmotic pressure, which increases net reabsorption. I stimulate the sodium/potassium ATPase on the basolateral membrane, the sodium/hydrogen countertransporter on the lumial memrane and the sodium/bicarbonate cotransporter on the basolateral membrane. This is done largely in the proximal tubule, and then in loop of Henle, distal tubule and collecting duct.
A. Parathyroid hormone
B. Atrial natiuretic peptide
C. Antidiuretic hormone
D. Angiotensin II
E. Aldosterone
D. Angiotensin II is part of the RAAS system. This is formed in the lung and locally in the kidney.
Who am I?
I act largely on the principal cells of the late distal tubule and cortical collecting tubule. I stimulate the sodium/potassium ATPase on the basolateral side of tubule membrane. I also inhance sodium permeability on the luminlnal side as well. I am stimulated by extracellular [K+].
A. Aldosterone
B. Antiotensin II
C. Antidiuretic hormone
D. Atrial natiuretic peptide
E. Parathyroid hormone
A. Released by the zona glomerulosa cells of the adrenal cortex, I am ALDOSTERONE! Another stimulus for aldosterone is Angiotensin II.
Who am I?
My principle action in the kidney is the reabsorption of calcium in the distal tubules and some in the loop of Henle. I also inhibit phosphate reabsorption in the proximal tubule and increase magnesium reabsorption in the loop of Henle.
A. Aldosterone
B. Antiotensin II
C. Antidiuretic hormone
D. Atrial natiuretic peptide
E. Parathyroid hormone
E. Parathyroid hormone
Who am I?
I am secreted in response to plasma volume expansion and increased atrial blood pressure. I directly inhibit the reabsorption of sodium and water in the collecting ducts. I also inhibit renin secretion and therefore the formation of angiotensin II. My goal is to increase urinary excretion and decrease blood volume.
A. Parathyroid hormone
B. Aldosterone
C. Antiotensin II
D. Antidiuretic hormone
E. Atrial natiuretic peptide
E. Atrial natiuretic peptide is released by the cells of the cardiac atria.
Who am I?
I bind to V2 receptors on the basolateral membrane of the late distal tubule, collecting tubules and collecting duct to increase the formation of cAMP. This activates protein kinases to phophorylate an intracellular protein aquaporin, which then moves to the luminal sideo f the membrane. Water channels are then created and I can achieve my goal of increase water reabsorption.
A. Atrial natiuretic peptide
B. Antiotensin II
C. Aldosterone
D. Parathyroid hormone
E. Antidiuretic hormone
E. Antidiuretic hormone
Chronic absence of ADH is known as diabetes insipidus; large amounts of dilute urine are then excreted.
