Does not show neutral amino acid transporter activity. Abundantly expressed in kidney, but not in intestine. Genetic variation in SLC6A18 is not a significant predictor for elevated systolic or diastolic blood pressure and is not associated with hypertension in the Japanese population (PubMed:16340170). Genetic variations in SLC6A18 might contribute to the disease phentotype in some individuals with iminoglycinuria or hyperglycinuria, that carry variants in SLC36A2, SLC6A19 or SLC6A20 (PubMed:19033659). Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A18 subfamily. The mouse ortholog protein is an active neutral amino acid transporter.