A 58-year-old man with a 10-year history of hypertension presents to the emergency department with acute onset severe headache, chest pain, and dyspnea. His blood pressure is 210/140 mmHg. Laboratory investigations reveal: serum creatinine 2.8 mg/dL (baseline 1.0), potassium 5.8 mEq/L, and urinalysis shows 3+ proteinuria with RBC casts. A diagnosis of hypertensive emergency with acute kidney injury is made. An ACE inhibitor is initiated. Which of the following best explains the acute rise in serum creatinine and hyperkalemia immediately after ACE inhibitor administration in this patient?