Answer
The tight junctions between epithelial cells of kidney tubules, prevent the diffusion of pump, transporter and channel proteins between apical, and basolateral membranes of the tubules.
Work Step by Step
The tight junctions of the cells in the epithelial membrane of kidney tubules face the tubular fluid; the basolateral membrane is in contact with the ISF. Tight junctions dictate that transport of substances from tubule to ISF space must be by the transcellular process. However, tight junctions in PCTs are leaky, and some fluid is resorbed by leaking around tight junctions --by paracellular resorption.
