CTL1s and CTL2s are not associated with the acetylcholine production, but transport choline together via the blood–brain barrier. Only CTL2s occur on the brain side of the barrier. They also remove excess choline from the neurons back to blood. CTL1s occur only on the blood side of the barrier, but also on the membranes of astrocytes and neurons.OCT1s and OCT2s are not associated with the acetylcholine production. They transport choline with low affinity. OCT1s transport choline primarily in the liver and kidneys; OCT2s in kidneys and the brain. Storage
Choline is stored in the cell membranes and organelles as phospholipids, and inside cells as phosphatidylcholines and glycerophosphocholines. Excretion
Even at choline doses of 2–8 g, little choline is excreted into urine in humans. Excretion happens via transporters that occur within kidneys (see transport). Trimethylglycine is demethylated in the liver and kidneys to dimethylglycine (tetrahydrofolate receives one of the methyl groups). Methylglycine forms, is excreted into urine, or is demethylated to glycine. Function
Choline and its derivatives have many functions in humans and in other organisms. The most notable function is that choline serves as a synthetic precursor for other essential cell components and signalling molecules, such as phospholipids that form cell membranes, the neurotransmitter acetylcholine, and the osmoregulator trimethylglycine (betaine). Trimethylglycine in turn serves as a source of methyl groups by participating in the biosynthesis of S-adenosylmethionine. Phospholipid precursor
Choline is transformed to different phospholipids, like phosphatidylcholines and sphingomyelins. These are found in all cell membranes and the membranes of most cell organelles.
Capillariasis is a disease caused by nematodes in the genus Capillaria. The two principal forms of the disease are:

Intestinal capillariasis, caused by Capillaria philippinensis
Hepatic capillariasis, caused by Capillaria hepatica


== References ==