The main hormone that acts on the kidneys to regulate sodium ion concentration of the extracellular fluid (ECF) is: 22:45 Biology Chapter 15 The main hormone that acts on the kidneys to regulate sodium ion concentration of the extracellular fluid (ECF) is: A) ADH B) renin C) secretin D) aldosterone E) epinephrine Answer: d Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+