Table 4:

Parameter values for the G protein activation cycles

symb.	parameter	value	reference
$k_s$	$G_{{\alpha }_s}$ activation rate	1–5s−1 (5s−1)	[9] (${\alpha }_{2a}$-adrenergic recept.)
$k_i$	$G_{{\alpha }_i}$ activation rate	5s−1	[9] (${\alpha }_{2a}$ adreno recept.)
$d_s$	$G_{{\alpha }_S^{GTP}}$ hydrolysis rate	0.04, 0.07s−1(0.07s−1)	[9]
$d_i$	$G_{{\alpha }_i^{GTP}}$ hydrolysis rate	0.03s−1	[9]
$k_{\beta s}$	$G_{{\alpha }_s^{GDP}}-\beta \gamma$ assoc. rate	0.7μM−1s−1	[9] (estimate)
$k_{\beta i}$	$G_{{\alpha }_i^{GDP}}-\beta \gamma$ assoc. rate	0.7μM−1s−1	[9] (rat, bovine)
$d_{\beta s}$	${\mathrm{G}}_{{\alpha }_s^{GDP}\beta \gamma }$ dissoc. rate	18.9 · 10−3s−1	[9] (estimate)
$d_{\beta i}$	${\mathrm{G}}_{{\alpha }_i^{GDP}\beta \gamma }$ dissoc. rate	0.14 · 10−3s−1	[9] (estimate)
$K_{r_{1}s}$	EP2-${\mathrm{G}}_{{\alpha }_s^{GTP}\beta \gamma }$ dissoc. const.	0.8μM	[9] ($\beta$-adrenergic recept.)
$K_{r_{2}s}$	EP4-${\mathrm{G}}_{{\alpha }_s^{GTP}\beta \gamma }$ dissoc. const.	0.088μM	[38] (human)
$K_{r_{2}i}$	EP4-${\mathrm{G}}_{{\alpha }_i^{GTP}\beta \gamma }$ dissoc. const.	50, 175, 214nM (214nM)	[38] (human)
$a_s$	total $G_{{\alpha }_s}$ concentration	2.3μM	[9] (myocyte)
$a_i$	total $G_{{\alpha }_i}$ concentration	8μM	[9] (neutrophils)
$b_1$	total $G_{\beta \gamma }$ concentr. EP2	0.005μM	[9] (neutrophils, estim.)
$b_2$	total $G_{\beta \gamma }$ concentr. EP4	1.8μM	[9] (estimate)
${\sigma }_0$	binding ratio for crosstalk	0.5/0.7	assumed