• Renin 
    • Released by juxtaglomerular cells (located in distal tubule of the kidney) when BP is low 
      • Also activated by sympathetic nervous response 
      • Also activated when macula densa cells (in distal convoluted tubule) sense low levels of salt 
    • Eventually leads to production of angiotensin II aldosterone, ADH
      • Renin cleaves the plasma protein angiotensinogen to form angiotensin I, which is cleaved to form angiotensin II