These cells have a contractile property similar to vascular smooth muscles and thus play a role in “regulating GFR” by altering the vessel diameter.

At this location, in the wall of the last portion of distal straight tubule, there is a modified region of tubular epithelium called the macula densa.(Fig.

5 in Kumaran and Hanukoglu 2020)[5] Cells in the macula densa respond to changes in the sodium chloride levels in the distal tubule of the nephron via the tubuloglomerular feedback (TGF) loop.

[2][3] The macula densa's detection of elevated sodium chloride, which leads to a decrease in GFR, is based on the concept of purinergic signaling.

[6][7] An increase in the salt concentration causes several cell signals (e.g. adenosine release) that leads to constriction of the adjacent afferent arteriole.