Other biochemical changes resulting from activation include Hydrolysis of membrane phospholipids Inhibition of adenylate cyclase Mobilization of intracellular calcium Phosphorylation of intracellular proteins Arachidonic acid is converted to thromboxane A2; this reaction requires platelet cyclooxygenase and is inhibited irreversibly by aspirin and reversibly by many NSAIDs (nonsteroidal anti-inflammatory drugs).