Which of the following ions are actively secreted into the filtrate by tubular cells of nephron during urine formation ?

Options

A. `NH_3,H^+,Na^(+)`
B. `Na^+,K^+,NH_3`
C. `K^+H^+,HCO_3^-`
D. `K^+NH_3,H^+`

Answer

To solve the question about which ions are actively secreted into the filtrate by tubular cells of the nephron during urine formation, we can follow these steps:

### Step 1: Understand the Process of Tubular Secretion
- Tubular secretion is a process that occurs in the nephron, specifically in the proximal convoluted tubule, distal convoluted tubule, and collecting duct. It involves the active transport of certain ions and molecules from the blood into the tubular fluid (filtrate).

### Step 2: Analyze Each Option
- **Option 1: Ammonia, Hydrogen ion, and Sodium ion**
- Sodium ions are primarily reabsorbed, not secreted. Therefore, this option is incorrect.

- **Option 2: Sodium, Potassium Ions, and Ammonia**
- Similar to option 1, sodium ions are reabsorbed rather than secreted. This option is also incorrect.

- **Option 3: Potassium Ions, Hydrogen Ions, and Bicarbonates**
- While potassium ions and hydrogen ions can be secreted, bicarbonates are primarily reabsorbed in the distal convoluted tubule. Thus, this option is incorrect.

- **Option 4: Potassium ions, Ammonia, and Hydrogen ions**
- This option includes potassium ions, ammonia, and hydrogen ions, all of which are actively secreted into the filtrate during urine formation. Therefore, this option is correct.

### Step 3: Conclusion
- The correct answer to the question is **Option 4: Potassium ions, Ammonia, and Hydrogen ions**.