Location and Mechanisms of Tubular K+ Transport (Friday 10/11/17)

Question 1

LO: Define the key elements to whole body potassium balance, including its distribution between body compartments

Answer 1

• Potassium normal plasma balance: 4.5 mM
• Rise in potossium: above 4.5mM. Excitable cells depolarise, causes increased risk of cardia arrest. Above 7mM causes death.
• Falll in potassium: hypokalemoia if falls below 4.5mM. Low pottassium causes excitable cells to hyperpolarise, potassoium leaves the cell, harder for the muscles to become excitable, as they can’t be depolarised. This causes muscle weakness, lethargy, and even paralysis. It also causes abnormal neaural conduction, so have defective cognitive function, causing confusion. Below 2mM causes coma and death. They have increased cardiac excitrability however due to faster recovery from AP.
• In cells have 140mM pottasium conc- accumulates in cell. Total in all cells, 4,000 mili mol
• ECF (interstitial and plasma) have 4.5mM conc of potassium. 50 mili mol
• In meals consume 100 mili mol per day. As it is absorbed through the blood stream, it is taken up by cells (rbc, muscle cells and hepatocytes) so the pottasium doesn’t stay in the plasma. Cells act as a buffer. This uptake by cells is stimulated by insulin, aldosterone and adrenalin.
• meal- rapid cell buffereing- potassium elimination by kidney.

Question 2

LO: Describe the renal tubular handling of potassium

Answer 2

• Pottasium reabsorbtion:
• 70% in proximal tubule
• 20% in loop of henle
• distal tubule and collecting tubule 10% on low pottasoim diet. In high potassoum diet 0-180%.
• Mechanisms of Tubular K+ handling: see slide

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Question 3

LO: Describe the control of renal potassium excretion

Answer 3

LO:

Question 4

LO: Describe the endocrine functions of the kidney, including erythropoietin and vitamin D metabolism

Answer 4

LO: