The term for the active transport of substances from blood into the filtrate is secretion.
Secretion is a critical process that occurs in the kidneys as part of urine formation. During this process, various substances, including ions, acids, and drugs, are actively transported from the bloodstream into the renal tubules, where they become part of the filtrate (the fluid that will eventually become urine). This helps to regulate the body’s electrolyte balance and remove waste products from the blood.
Unlike filtration, which occurs passively based on pressure differences, secretion requires energy in the form of ATP to move substances against their concentration gradient. This ensures that the body can efficiently eliminate substances that are not needed or could be harmful if they remain in the bloodstream.