This document discusses renal hormones and their functions. It describes the juxta-glomerular apparatus, which contains specialized cells that regulate renin secretion and the renin-angiotensin system. It also discusses how hormones like vitamin D and erythropoietin are synthesized and activated in the kidneys to regulate calcium homeostasis, red blood cell production, and other endocrine functions. The kidneys play a key role in endocrine and paracrine signaling through the production of hormones and local factors.

1. DR. POOJA PRIYADARSINI
SENIOR RESIDENT
DEPARTMENT OF BIOCHEMISTRY
AIIMS, BHUBANESWAR
RENAL
HORMONES.

2. OBJECTIVES.
❖ INTRODUCTION
❖ COMPONENTS OF RAS
❖ PATHOPHYSIOLOGY OF RAS
❖ KALLIKREIN-KININ SYSTEM
❖ VITAMIN D
❖ ERYTHROPOIETIN

3. INTRODUCTION
■ The kidney -- Essential role in the
maintenance of life in higher organisms
■ Regulation of the blood pressure and
body fluid homeostasis
■ Removal of wastes
■ As a major Endocrine organ.

4. ENDOCRINE FUNCTIONS
■ Renin
■ kallikreins
■ 1,25- (OH)2 vitamin D3,
■ Erythropoietin

5. TARGET ORGAN
■ The kidney serves as an
important endocrine target
organ for a number of
hormones
■ Controls the
 extracellular fluid volume,
 electrolyte balance
 Acid-base balance
 blood pressure.
■Angiotensin
■Aldosterone
■PTH
■ADH

6. “Local hormones,”
■ The kidney
is also a major organ
for the production
and action of various
“local hormones,” or
autocrine/paracrine
regulators
■ such as
 Prostaglandins
(PGs),
 Adrenomedullin
(AM)
 Endothelins (ETs).

7. Renin Angiotensin System
(RAS)
■ Major component
of RAS is:
“Juxta-glomerular
Apparatus"
■ Collection of
specialised cells
located near to
glomerulus.

8. JUXT-GLOMERULAR
APPARTUS.
■ TYPES OF CELLS in
JG Apparatus
 Juxta-
glomerular cells
 Macula densa
cells
 Mesangial
cells/Lacis cells

9. JUXTA-GLOMERULAR CELLS
■ Specialised
myoepithelial cells
■ Location – Tunica
Media of afferent
arteriole

10. CHARACTERISTIC FEATURES
• They have well developed
Golgi appartus,
Endoplasmic reticulum,
abundunt mitochondria &
Ribosomes.
• Renin is stored in the secretory
granules of JG cells and, therefore,
these are also called Granular cells

11. TYPE OF RECEPTOR
■ Baroreceptors
(tension receptors)
■ Respond to changes in
the transmural
pressure gradient
between the afferent
arterioles and the
interstitium.

12. RESPONSE
■ Densely innervated by the sympathetic
nerve fibers and release their renin
content in response to the
Sympathetic discharge.
■ Vascular volume receptors(monitor renal
perfusion pressure)are stimulated by
hypovolaemia or decreased renal
perfusion pressure.

13. MACULA DENSA CELLS
■ Specialised renal
tubular epithelial cells
of a short segment of
the distal convoluted
tubule which passes
between the afferent
and efferent
arterioles.

15. Characteristic features
■ They are not well adapted for reabsorption.
■ They are not innervated.
■ These cells are in direct contact with the
mesangial cells
■ and in close contact with the JG cells.
■ They act as chemoreceptors
■ Stimulated by decreased NaCl concentration

16. Mesangial cells.
■
■
■
■
Interstitial cells of the JG apparatus.
They are in contact with both the macula densa cells (on
one side) and JG cells (on the other side).
Relay the signals from
macula densa to the granular cells after modulating the
signals.
In this way, a decreased intraluminal Na+ load, Cl– load, or
both in the region of macula densa stimulates the JG cells
to secrete renin

17. REGULATION OF GFR
■Auto regulation
■Hormonal regulation
■Nervous regulation

18. GFR DEPENDS ON DIAMETERS OF
AFFERENT AND EFFERENT ARTERIOLES
↑GFR ↓GFR
Glomerulus
Afferent arteriole Efferent arteriole
Glomerular filtrate
Aff. Art. dilatation
Eff. Art. dilatation
Eff. Art.
constriction
Aff. Art.
constriction
Prostaglandins,
Kinins, Dopamine
(low dose), ANP,
NO
Angiotensin II
(low dose)
Angiotensin II
blockade
Ang II (high dose),
Noradrenaline (Symp
nerves), Endothelin,
ADH, Prost. Blockade)

19. AUTO REGULATION
■ Mechanism of Auto-regulation
1 Myogenic mechanism ( Respond to
change in arterial pressure).
2 Tubuloglomerular feedback
mechanism ( Respond to change in NaCl
concentration of tubular fluid.

20. HORMONAL REGULATION
■HORMONES
VASOCONSTRIC
TORS
1 NE
2 Angiotensin II
3Endothelin
VASODIALATORS
1 PG
4 NO
5 ANP
6 Bradykinin
■ STIMULUS GFR
ECV
ECV
ECV
ECV, stretch NC
stretch, Ach, histamine
ECV
PG, ACE

21. NERVOUS REGULATION
■ Afferent & efferent arterioles– innervated by
sympathetic nerves from T4-L2 through
splanchnic nerves.
■ Normally sympathetic tone minimum.
■ Mild to moderate stimulation – mild effect.
■ Strong acute stimulation – Fall in RBF due to
constriction of both afferent & efferent arterioles.

22. KALLIKREINS – KININ SYSTEM
■ The kallikrein-kinin system consists of four
major components: kininogen,
■ kallikreins,
■ bradykinin
■ kininases

24. 1,25- (OH)2 vitamin D3,
■ Final activation of vitamin D to the active
hormone calcitriol takes place in
the kidneys – 1-hydroxylation of
25- hydroxycholecalciferol
1,25- dihydroxycholecalciferol.

26. Active vitamin D
■ Stimulates the small intestine for
protein synthesis allowing absorption
of Ca2+and phosphates.
■ Promotes renal reabsorption of Calcium
and Phosphorous.
■ This ensures the availability of
Ca2+and phosphate for bone growth.
Calcitriol simultaneously activates
osteoblasts to synthesize collagen.

28. ERYTHROPOIETIN
■ Erythropoietin is a peptide hormone
which regulates Erythropoiesis.
■ Erythropoietin is
a Glycoprotein contai ning 165 amino
acids.

29. Actions
■ Receptors are present on the membranes
of red blood cell precursors.
■ Binding of the EPO reduces Apoptosis
of these cells – multiple cells survive
and can therefore complete their
development into mature erythrocytes.

31. Synthesis and inactivation
■ In adults, approximately 90
erythropoietin synthesized
% of
in the
kidneys (interstitial cells)
Remaining amount in the liver (perivenous
hepatocytes) .

32. Synthesis and inactivation
■ The liver plays a key role in the production
of erythropoietin during the fetal period.
■ But in adulthood, the liver is no longer able
to compensate for a potential decrease in
production in the kidneys.

33. CLINICAL CORRELATIONS:
■ For most people in end-stage renal
failure, anemia with erythropoietin
deficiency occurs.
■ Doctors can administer recombinant
erythropoietin to these patients.

34. DOPING DRUG
■ Erythropoietin is also
abused as doping
substance – especially
in endurance athletics
(cycling) .

35. STIMULUS FOR
PRODUCTION.
■ Decrease in partial pressure of oxygen in
blood flowing through the organs.
■ Also supported by androgens &
catecholamines.