An antibiotic circulating in the blood passes through the kidneys. Only a miniscule amount of it passes from the glomerular capillary into the glomerular filtrate. When its presence in the urine is measured, it has been almost completely excreted. How is this possible?
A) During the process of reabsorption, flow of water across the tubular membrane into the peritubular capillary passively encourages the antibiotic to cross the opposite way.
B) Stimulation from nerves causes the efferent arteriole to constrict and force the antibiotic through the glomerular capillary into the filtrate.
C) The antibiotic is actively transported into the proximal tubule during tubular secretion.
D) Sodium ions crossing into the blood of the peritubular capillary increases osmotic pressure and forces the antibiotic into the proximal tubule.

Question

Quizplus · Accepted Answer

The antibiotic is actively transported into the proximal tubule during tubular secretion, which explains how it can be almost completely excreted despite a minuscule amount passing from the glomerular capillary into the glomerular filtrate initially.

An Antibiotic Circulating in the Blood Passes Through the Kidneys