The JGA plays a complex regulatory role A fall in glomerular blood flow/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II activates the adrenal cortex to release aldosterone. Aldosterone causes reabsorption of Na+and H2O from the distal parts of the tubule. This leads to an increase in blood pressure and GFR.
