The process of tubular secretion occurs in the epithelial cells in both of the renal tubules and the collecting ducts of the kidneys. The process helps the kidneys clean and filter the blood while producing urine.
Tubular secretion pulls substances into the tubular fluid for the substances to be excreted from the body in the form of urine. Substances and compounds that are secreted into the tubular fluid during tubular secretion include ions such as potassium, hydrogen and ammonium ions. Creatine, urea, hormones and certain drug metabolites are also secreted into the tubular fluid via the process of tubular secretion. These substances are all excreted from the body in the urine.