Tissues—Rodents
Concentration Range	Comments	Reference
	Review	[347]
32 nM increases to → 135 mM after dosing	Gerbil brain	[360]
1–16 mM	Rat ileum	[361]
~40 nM in plasma	Trebled after dosing at 5 mg/kg	[210]
Tissues—human
Concentration range	Comments	Reference
	Review	[305]
0.2–0.7 pmol/mg	Brain; 3× increase in Down syndrome	[362]
2–3 pmol/mg	Brain	[353]
Up to 1.58 pmol/mg	Brain	[363] and review [347]
1.6 mM	Colon	[359]
10.2 ng/mL	Fetal membrane	[364]
7.6 g/mL	Umbilical Cord	[364]
1 ng/mL	Placenta	[364]