A 62-year-old man presents to his primary care physician with a 2-year history of progressive urinary symptoms including hesitancy, weak urinary stream, and nocturia (3-4 times per night). He denies dysuria, hematuria, or abdominal pain. Vital signs are stable. Digital rectal examination reveals a smooth, uniformly enlarged prostate without nodules or tenderness. Post-void residual is 120 mL on ultrasound. Serum PSA is 2.1 ng/mL (normal <4 ng/mL). A diagnosis of benign prostatic hyperplasia (BPH) is confirmed. He is started on tamsulosin, a selective alpha-1A adrenergic antagonist. Which of the following best explains the mechanism by which tamsulosin improves his obstructive urinary symptoms?

1. A)Blockade of alpha-1A adrenergic receptors on smooth muscle in the prostatic urethra and bladder neck, reducing urethral resistanceGABARITO
2. B)Inhibition of 5-alpha reductase, preventing conversion of testosterone to dihydrotestosterone and reducing prostate volume
3. C)Competitive antagonism at muscarinic receptors in the detrusor muscle, increasing bladder compliance
4. D)Activation of beta-2 adrenergic receptors on bladder smooth muscle, promoting relaxation
5. E)Competitive inhibition of angiotensin II type 1 receptors, reducing prostate inflammation