جمعتكم مباركه 🌷
لعلها ساعة إجابة إدعوا الله بأن يفرج عن إخواننا في غزة ...فلا تكن عاجزاً حتى من الدعاء لهم .

🚨Reabsorption of K+
✅ involves an H+
, K+-ATPase in the luminal membrane of the α-intercalated cells.
✅ occurs only on a low-K+
diet (K+ depletion). Under these conditions, K+ excretion can be as low as 1% of the filtered load because the kidney conserves as much K+ as possible.
b. Secretion of K+
⭕ occurs in the principal cells.
⭕ is variable and accounts for the wide range of urinary K+
excretion.
⭕ depends on factors such as dietary K+
, aldosterone levels, acid–base status, and
urine flow rate.

✅Mechanism of distal K+ secretion :⬇️⬇️⬇️
(a) At the basolateral membrane, K+ is actively transported into the cell by the Na+–K+ pump.
As in all cells, this mechanism maintains a high intracellular K+concentration.
(b) At the luminal membrane, K+
is passively secreted into the lumen through K+channels.
The magnitude of this passive secretion is determined by the chemical and electrical driving forces on K+ across the luminal membrane.
✔️ Maneuvers that increase the intracellular K+concentration or decrease the luminal K+ concentration will increase K+ secretion by increasing the driving force.
✔️Maneuvers that decrease the intracellular K+ concentration will decrease K+secretion by decreasing the driving force.

📱Factors that change distal K+ secretion :
(a) Dietary K+
✔■ A diet high in K+
increases K+ secretion, and a diet low in K+ decreases K+secretion.
■ On a high-K+ diet, intracellular K+ increases so that the driving force for K+secretion also increases.
■ On a low-K+ diet, intracellular K+ decreases so that the driving force for K+secretion decreases. Also, the α-intercalated cells are stimulated to reabsorb K+ by the H+, K+-ATPase.
✔(b) Aldosterone
■ increases K+ secretion.
■ The mechanism involves increased Na+ entry into the cells across the luminal membrane and increased pumping of Na+ out of the cells by the Na+–K+pump.
Stimulation of the Na+–K+ pump simultaneously increases K+ uptake into the principal cells, increasing the intracellular K+ concentration and the driving force for K+secretion.
Aldosterone also increases the number of luminal membrane K+
channels.
■ Hyperaldosteronism increases K+ secretion and causes hypokalemia.
■ Hypoaldosteronism decreases K+ secretion and causes hyperkalemia
✔Acid–base
■ Effectively, H+ and K+ exchange for each other across the basolateral cell
membrane.
■ Acidosis decreases K+ secretion. The blood contains excess H+; therefore, H+enters the cell across the basolateral membrane and K+ leaves the cell.
As a result, the intracellular K+ concentration and the driving force for K+secretion decrease.
■ Alkalosis increases K+ secretion. The blood contains too little H+, therefore, H+leaves the cell across the basolateral membrane and K+ enters the cell. As a result, the intracellular K+
concentration and the driving force for K+secretion increase.

✔Thiazide and loop diuretics
■ increase K+ secretion.
■ Diuretics that increase flow rate through the distal tubule and collecting ducts (e.g., thiazide diuretics, loop diuretics) cause dilution of the luminal K+concentration, increasing the driving force for K+ secretion.
Also, as a result of increased K+ secretion, these diuretics cause hypokalemia.
K+
✔K-sparing diuretics
■ decrease K+ secretion
If used alone, they cause hyperkalemia.
■ Spironolactone is an antagonist of aldosterone; triamterene and amiloride act directly on the principal cells.
■ The most important use of the K+-sparing diuretics is in combination with thiazide or loop diuretics to offset (reduce) urinary K+losses.
✔Luminal anions
■ Excess anions (e.g., HCO3
-) in the lumen cause an increase in K+ secretion by increasing the negativity of the lumen and increasing the driving force for K+secretion.🖋
⚡️⚡️⚡️⚡️⚡️⚡️⚡️⚡️⚡️⚡️
👍⭐❤

Question
Acetazolamide causes the following ❓
a. metabolic acidosis
b. hyperkalaemia
c. hypernatraemia
d. renal calculi
e. hypercalcaemia

❓Which books is better to read in physiology?