What effect does prostaglandin E2 (PGE2) have on smooth muscle cells?

Prostaglandin E2 (PGE2) primarily functions through its various receptor subtypes, including EP2 and EP4, which are Gs protein-coupled receptors. When PGE2 binds to these receptors, it leads to an increase in intracellular cyclic AMP (cAMP) levels. This rise in cAMP activates protein kinase A (PKA), which ultimately results in the relaxation of smooth muscle cells.

The relaxation effect is mediated through several mechanisms, including the inhibition of calcium release from the sarcoplasmic reticulum and the promotion of myosin light chain phosphatase activity, which dephosphorylates myosin light chains, leading to a decrease in contraction. As a result, PGE2 causes smooth muscle relaxation, particularly in vascular smooth muscle, where it plays a role in the regulation of blood flow and blood pressure.

In contrast to this, other options suggest different mechanisms or effects of PGE2 that do not align with its primary function in smooth muscle physiology. For example, while PGE2 does activate certain phospholipases in other contexts, the primary action in smooth muscle relaxation is through cAMP signaling and not through activation of phospholipase A2. Additionally, PGE2 does