Final answer:
High renal plasma clearance indicates effective clearance of substances from the blood by the kidneys, which may also suggest heightened filtration efforts due to conditions like renal stenosis.
Step-by-step explanation:
High renal plasma clearance indicates that a substantial volume of plasma is effectively cleared of a particular substance by the kidneys in a given time frame. For instance, para-aminohippuric acid (PAH) is used to measure renal plasma flow because all of the PAH that passes through the kidneys is excreted in urine, providing a measure of plasma flow through the kidneys. Creatinine, a metabolic byproduct of muscle, is used to calculate the glomerular filtration rate (GFR), which reflects how well the kidneys filter blood. A high clearance rate can signify effective renal excretion function but can also indicate conditions such as renal stenosis where filtration fraction increases as the kidney works harder to maintain fluid and electrolyte balance in reduced blood flow.