WBR0387
| Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::A researcher, studying the role of aldosterone at the level of renal tubules, measures the urinary concentration of sodium, potassium, and hydrogen before and after aldosterone administration. With respect to urinary concentrations before the administration of aldosterone, which of the following parameters is true for concentrations of urinary sodium, potassium, and hydrogen (in order) following aldosterone administration?
|
| Answer A | AnswerA::Increased - Decreased - Decreased |
| Answer A Explanation | AnswerAExp::An increase in sodium, accompanied by a decrease in potassium and hydrogen, occurs in the serum, not in urine. |
| Answer B | AnswerB::Increased - Increased - Decreased |
| Answer B Explanation | [[AnswerBExp::Following aldosterone administration, urinary sodium is decreased due to the reabsorption of sodium and urinary hydrogen is increased due to the excretion of hydrogen.]] |
| Answer C | AnswerC::Decreased - Increased - Increased |
| Answer C Explanation | [[AnswerCExp::Aldosterone accelerates the ion exchange of sodium for potassium or hydrogen, increasing the reabsorption of sodium and the excretion of both potassium and hydrogen.]] |
| Answer D | AnswerD::Decreased - Increased - Unchanged |
| Answer D Explanation | [[AnswerDExp::Following aldosterone administration, hydrogen is excreted into the urine.]] |
| Answer E | AnswerE::Decreased - Decreased - Increased |
| Answer E Explanation | [[AnswerEExp::Following aldosterone administration, urinary potassium increases and serum potassium decreases due to the excretion of potassium.]] |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::Aldosterone accelerates the ion exchange of sodium for potassium and hydrogen. Aldosterone acts at the level of collecting ducts to reabsorb sodium, and excrete potassium and hydrogen. Thus, urinary concentrations of sodium will decrease, while urinary concentrations of potassium and hydrogen will increase. Educational Objective: Aldosterone, which acts on the renal collecting tubule, accelerates the ion exchange of sodium for potassium and hydrogen, allowing for the increased reabsorption of sodium and excretion of both potassium and hydrogen. |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
