A researcher is studying the effects of a new antihypertensive medication on urine osmolality. She first measures urine osmolality in different parts of the nephron of a healthy human control. The findings are shown below: Portion of nephron Urine osmolality (mOsmol/kg) Proximal convoluted tubule 300 Loop of Henle, descending limb 1200 Loop of Henle, ascending limb 200 Distal convoluted tubule 100 Collecting duct 600 Which of the following is the most likely explanation for the urine osmolality in the ascending limb of the loop of Henle?
AIncreased urea excretion
BIncreased transcription of water channels
CImpermeability to water
DIncreased bicarbonate reabsorption
EImpermeability to sodium
A 42-year-old man is brought to the emergency room because of confusion. His wife says he has been urinating more frequently than usual for the past 3 days. He has not had fever or dysuria. He has bipolar disorder, for which he takes lithium. His pulse is 105/min, and respirations are 14/min. He is lethargic and oriented only to person. Physical examination shows dry mucous membranes and increased capillary refill time. Laboratory studies show a serum sodium concentration of 158 mEq/L and an antidiuretic hormone (ADH) concentration of 8 pg/mL (N = 1–5). Which of the following is the most likely site of dysfunction in this patient?
AHypothalamic supraoptic nucleus
BDescending loop of Henle
CJuxtaglomerular apparatus
DCollecting duct
EPosterior pituitary gland
A 66-year-old man with congestive heart failure presents to the emergency department complaining of worsening shortness of breath. These symptoms have worsened over the last 3 days. He has a blood pressure of 126/85 mm Hg and heart rate of 82/min. Physical examination is notable for bibasilar crackles. A chest X-ray reveals bilateral pulmonary edema. His current medications include metoprolol succinate and captopril. You wish to add an additional medication targeted towards his symptoms. Of the following, which statement is correct regarding loop diuretics?
ALoop diuretics can cause metabolic acidosis
BLoop diuretics can cause ammonia toxicity
CLoop diuretics can cause hyperlipidemia
DLoop diuretics decrease sodium, magnesium, and chloride but increase calcium
ELoop diuretics inhibit the action of the Na+/K+/Cl- cotransporter
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