Regulation of Kidney Function
(i) Control by Antidiuretic Hormone (ADH) :- Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis. An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release to complet the feedback. ADH can also affect the kidney function, by its constrictory effects on blood vessels. This causes an increase in blood pressure. An increase in blood pressure can increase the glomerular blood flow and thereby the GFR. In this situation, the osmoreceptor cells also promote thirst. Drinking reduces the osmolarity of the blood, which inhibits the secretion
of ADH, thereby completing the feedback circuit.
(ii) Control by Juxtaglomerular Apparatus (JGA) :- JGA operates a multi-hormonal Renin Angiotensin-
Aldosterone System (RAAS). Whenever there is a fall in Glomerular blood flow/ Glomerular blood pressure/ GFR can activate J.G. cells to release an enzyme called renin, into the blood stream. In the blood, renin initiates chemical reactions that convert a plasma protein, called
angiotensinogen to a peptide, called angiotension II, which works as a hormone. Angiotensin II being
a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. It also increases
blood volume in two ways.
(1) Firstly, by signaling the proximal convoluted tubules to reabsorb more NaCl and water.
(2) Secondly, by stimulating the adrenal gland to release aldosterone, a hormone that induces the
distal convoluted tubule to reabsorb moreNa+ and water. This leads to an increase in blood volume
and pressure, completing the feedback circuit by supporting the release of renin.
(iii) Atrial Natruretic Factor (ANF):
� When BP or blood volume rise, then the wall of atria of the heart release ANF.
� This ANF cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure.
� ANF also inhibits the release of renin from the kidney and check on the renin angiotensin mechanism.
of ADH, thereby completing the feedback circuit.
(ii) Control by Juxtaglomerular Apparatus (JGA) :- JGA operates a multi-hormonal Renin Angiotensin-
Aldosterone System (RAAS). Whenever there is a fall in Glomerular blood flow/ Glomerular blood pressure/ GFR can activate J.G. cells to release an enzyme called renin, into the blood stream. In the blood, renin initiates chemical reactions that convert a plasma protein, called
angiotensinogen to a peptide, called angiotension II, which works as a hormone. Angiotensin II being
a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. It also increases
blood volume in two ways.
(1) Firstly, by signaling the proximal convoluted tubules to reabsorb more NaCl and water.
(2) Secondly, by stimulating the adrenal gland to release aldosterone, a hormone that induces the
distal convoluted tubule to reabsorb moreNa+ and water. This leads to an increase in blood volume
and pressure, completing the feedback circuit by supporting the release of renin.
(iii) Atrial Natruretic Factor (ANF):
� When BP or blood volume rise, then the wall of atria of the heart release ANF.
� This ANF cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure.
� ANF also inhibits the release of renin from the kidney and check on the renin angiotensin mechanism.