Progesterone directly upregulated endothelial nitric oxide synthase (eNOS) expression in human endothelial cells. Progesterone augmented eNOS promoter activity through a progesterone receptor A- and specificity protein-1-dependent manner. Antagonism of the progesterone receptor reduced eNOS expression and impaired vasodilation in rats.

Progesterone promotes endothelial nitric oxide synthase expression through enhancing nuclear progesterone receptor-SP-1 formation | American Journal of Physiology-Heart and Circulatory Physiology