Table 2.

The following considerations exist with regard to the basolateral monoamine organic cation transporters of the proximal convoluted renal tubule cells^*

	Phase 1	Phase 2	Phase 3
Serotonin or dopamine transporter entrance gates	Partially closed	Open	Open
Transporter lumen saturation	Unsaturated	Unsaturated	Saturated

Note:

^*In Phase 1, the serotonin and dopamine gates are partially closed, restricting access to the transporter. In Phases 2 and 3, the gates are open, allowing full access to the transporter by serotonin and dopamine. In Phases 1 and 2, the lumen of the transporter is not saturated with serotonin and dopamine. In Phase 3, the lumen of the transporter is saturated with serotonin or dopamine.5