Figure 30

Figure 30 Deleterious effects of low oxygen (O₂ ) levels on intracorporeal smooth muscle. Low O₂ tension promotes the release oftransforming growth factor β₁ (TGF-β₁ ), which acts on TGF-β₁ receptors to stimulate the production of collagen-inducing fibrosis. In contrast, high O₂ tension, as occurs during nocturnal erections, stimulates the production of prostaglandin E₁ (PGE₁ ) which, in turn with forskolin, stimulates adenylate cyclase to produce cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). cAMP induces and maintains healthy smooth muscle activity. PDE, phosphodiesterase; PGS, prostaglandin synthase