28. Vasopressin

Question 1

How does vasopressin exert its action in the body

Answer 1

GPCR
seven transmembrane spanning domains

V1 V2 V3
OTR P2R

Question 2

V1 receptors

Answer 2

V1 receptors
Vascular smooth muscle
heart
kidney
Hepatocytes
Bladder
spleen
platelets
adipocytes

Gq coupled actiation Phospholipase C
- release intracellular Ca++
mediates vascular vasoconstriction
(exacerbated in hypovol to maintain perfusion)

Vasodilation of pulmonary and cerebral vessel
NO mediated action

Question 3

V2 receptors

Answer 3

Found on DCT
CD kidney

Essential osmolality and plasma volume control

GPRC activate of AC
- ↑cAMP

Activation aquaporin channels

↑H2O reabsorption
Antidiuretic effect

Also on endothelial cells
stimulates release vWF
important role in platelet aggregation + binding where bleeding occurs

Question 4

V3 rec

Answer 4

Gq protein coupled activation
↑ intracell Ca

CNS action vasopressin
Neurotransmitter modulating control 
memory
BP 
Core temp
Release Pit hormone

Question 5

OTR

Answer 5

Endothelial cells reproductive organs
vascular endothelium
heart

Actions include uterine vasoconstriction
NO mediated vasodilation
ANP release

Question 6

P2R

Answer 6

Cardiac endothelium + myocardium

Stim causes selective coronary vdil
↑ Contractility

Question 7

Clinical Uses

Answer 7

1, Diabetes insipidus

2. Oesophageal varices
3. Bleeding and Coagulopathy
4. Shock
5. Neuroendocrine tumour resection

Question 8

Diabetes insipidus

Answer 8

• Intranasal or I desmopressin use to Rx cranial DI
  2nd to TBI
  SAH
  Neoplasm

Reduce Polyuria

Question 9

Oesophageal varices

Answer 9

Terlipressin
- synthetic long acting vasopressin analogue

decreases

1) Portal flow
2) hepatic venous pressure gradient
3) variceal pressure during haemorrhage

Question 10

Bleeding and Coagulopathy

Answer 10

Desmopressin
Synthetic analogue of vaso
Mild forms haemophilia A. vWD.
Conditions impair platelet function 2nd to renal failure
drugs to increase efficiency of plt activation and coag

Question 11

Shock

Answer 11

Beneficial HD effects in septic shock
unresponsive to conventional vsopressors

Refractory Haemorrhage + anaphylactic shock
response to 
fluid / blood / catecol poor
?acidosis
?receptor down reg
?NO induced vdil

Question 12

Neuroendocrine tumour resection

Answer 12

Rx of catecholamine resistant hypotension

post phae removal

Question 13

Organ donation

Answer 13

Helps preserve organ function
less likely cause met acidosis
P.HTN
Reduces inotropes in post Brainstem death
before surgery
Rx DI