Most tissue histamine is sequestered and bound in:

Correct Answer: A

Rationale: The correct answer is A: Granules in mast cells or basophils. Mast cells and basophils are well-known for storing histamine in their granules. Upon stimulation, these cells release histamine into the surrounding tissues. Histaminergic neurons (choice B) primarily release histamine in the brain and are not the main reservoir of tissue histamine. Enterochromaffin-like cells (choice C) are found in the stomach and release histamine into the bloodstream, not sequestering it in tissues. Therefore, the correct choice is A as most tissue histamine is indeed sequestered and bound in granules in mast cells or basophils.

Correct Answer: D

Rationale: The correct answer is D. This is because all three statements A, B, and C are true regarding nutritional supplements. A: Nutritional supplements are intended to supplement the diet and contain dietary ingredients like vitamins, minerals, herbs, amino acids, etc. B: Nutritional supplements are regulated as foods by the FDA, not drugs. C: Nutritional supplements do not require pre-approval for safety and efficacy, unlike drugs. Therefore, all of the statements are true, making option D the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Probucol (Lorelco). Probucol decreases blood levels of HDL by inhibiting the enzyme that helps in the production of HDL. Lovastatin (A) works by lowering LDL levels, Nicotinic acid (B) increases HDL levels, and Gemfibrozil (C) works mainly on triglycerides and raises HDL levels. Probucol (D) is specifically known for lowering HDL levels.

Correct Answer: C

Rationale: The correct answer is C: Hypophosphatemia. Etidronate is a bisphosphonate used to treat Paget's disease and osteoporosis by inhibiting bone resorption. Hypophosphatemia is a condition characterized by low phosphate levels in the blood, and etidronate is not indicated for this. Hypercalcemia is not an indication for etidronate as it can further decrease calcium levels.

Correct Answer: B

Rationale: The correct answer is B: Furosemide (Lasix). Furosemide is a loop diuretic that specifically targets the sodium/potassium/chloride cotransporter in the thick ascending loop of Henle. By blocking this transporter, furosemide inhibits sodium reabsorption, leading to increased diuresis. Acetazolamide works in the proximal tubule, hydrochlorothiazide acts on the distal convoluted tubule, and amiloride targets the epithelial sodium channels in the collecting duct. Therefore, they are not the correct choices for blocking the sodium/potassium/chloride cotransporter in the thick ascending loop of Henle.