PDE isozyme (and subtype)

Substrate

Specificity

Tissue Distribution

PDE1

(A, B)

cAMP < cGMP

Heart, skeletal muscle, brain, liver, vascular smooth muscle

PDE2

(A)

cAMP = cGMP

Heart, brain, skeletal muscle, adrenal cortex, corpus caverrnosum

PDE3

(A, B)

cAMP > cGMP

Heart, brain, corpus cavernosum, vascular and visceral muscle, platelets, liver, kidney

PDE4

(A, B, C, D)

cAMP > cGMP

Brain, testes, skeletal, visceral and vascular muscle, heart, leukocytes

PDE5

(A)

cGMP > cAMP

Corpus cavernosum, platelets, visceral and vascular muscle, pancreas, brain, liver, lung