Biology of Disease

MECHANISMS OF HORMONAL ACTION

CZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY &+(

Figure 7.7 Examples of hormone secondary messengers. (A) cAMP, (B) cGMP, (C) a hydrated
Ca2+, (D) inositol triphosphate (IP 3 ) and (E) a diacylglycerol (DAG).

Figure 7.8 Mechanism of action of a hormone

that acts through the second messenger, cAMP.

Note the conformational changes that are shown

schematically as (A) the hormone binds to its

receptor, (B) and (C) to the trimeric G protein as GDP

and GTP are exchanged and to the (D) adenylate

cyclase (AC) as it is activated by the GA-GTP complex.

Adenine

O

O

O

O

O

P OH

O

O

P

Guanine

O

O

OOH

Ca^2 +

OH 2

OH 2

OH 2

OH 2

H 2 O

H 2 O

H 2 O

P

P

P

OH

OH

OH

H

OH

O

O

O

O

D)

A)

B)

C)

E)

• 
  


• 
  

  GDP

  
  

GTP

ATPcAMP

AC

AC

AC

AC

GDP

GTP

H

H

H

H

GTP

GDP

A)

B)

C)

D)