Table 2:

Description of model variables

	model	symbol	description
ligand receptor binding	(5)	$p$	PGE2 concentration
		$r_{1/2}$	inactive EP2/EP4 concentration
		$r_{1/2}^{\mathrm{*}}$	activated EP2/EP4 concentration
$G$ protein activation cycles	(7),(10)	${\alpha }_{s/i}$	$G_{{\alpha }_{s/i}^{GDP}}$ concentration
		${\alpha }_{s/i}^{\mathrm{*}}$	$G_{{\alpha }_{s/i}^{GTP}}$ concentration
		$\beta$	$G_{\beta \gamma }$ concentration
		${\beta }_{s/i}$	$G_{{\alpha }_{s/i}^{GDP}\beta \gamma }$ concentration
cAMP production	(11)	$w$	cAMP concentration