Basal AC influx of cAMP (r1):

υ_{1} = k_{11};

Basal GC influx of cGMP (r2):

Υ_{2} = k_{12};

cAMP turnover via PDE2 (r3):

${\upsilon}_{3}={k}_{1}\cdot {{x}_{1}}^{{k}_{19}}\cdot {x}_{3}/\left({k}_{2}+{{x}_{1}}^{{k}_{19}}\right);$

cAMP turnover via PDE3 (r4):

υ_{4} = k_{3}·x_{4}·x_{1}/(k_{4}+x_{1});

cGMP turnover via PDE2 (r5):

υ_{5} = k_{5}·x_{3}·x_{2}/(k_{6}+x_{2});

cGMP turnover via PDE3 (r6):

υ_{6} = k_{7}·x_{4}·x_{2}/(k_{8}+x_{2});

cGMP turnover via PDE5 (r7):

υ_{7} = k_{9}·x_{5}·x_{2}/(k_{10}+x_{2});

(De)activation of PDE (r8 r13):

υ_{8} = k_{14}·x_{6};


υ_{9} = k_{13}·x_{3};


υ_{10} = k_{16}·x_{7};


υ_{11} = k_{15}·x_{4};


υ_{12} = k_{18}·x_{8};


υ_{13} = k_{17}·x_{5};
