When scientists put the human creatine transporter into frog cells, they found it needs sodium and chloride to move creatine into the cells, and it works best when there's about 20 millionths of a gram of creatine per milliliter of fluid.

Scientists found that for the creatine transporter to move creatine into frog cells, it needs at least two sodium ions and one chloride ion for each creatine molecule, based on how the uptake rate changed with different sodium and chloride concentrations.

A chemical called gamma-aminobutyric acid can block the creatine transporter in frog cells, but it takes about 6.5 thousandths of a gram per milliliter to block half of the transporter's activity, which is much less potent than other inhibitors tested.

When scientists changed one amino acid in the creatine transporter (from alanine to proline at position 285), it didn't change how well beta-guanidinopropionic acid, cyclocreatine, or gamma-guanidinobutyric acid could block the transporter in frog cells.

Another chemical called cyclocreatine also blocks the creatine transporter in frog cells, but it takes about 370 millionths of a gram per milliliter to block half of the transporter's activity, which is less potent than beta-guanidinopropionic acid.

A chemical called beta-guanidinopropionic acid blocks the creatine transporter in frog cells, and it takes about 44 millionths of a gram per milliliter to block half of the transporter's activity.