Hello,
You can program a 2450 SMU to sink current and measure voltage. See attached PNG for reference to the power envelope for this unit. If sinking up to 1A, you will be limited up to 20V, and if sinking up to 100mA, you will be limited up to 200V.
If you need to maintain a steady 1uOhm load resistance, your V and I will need to stay fixed. If your voltage changes for example, you will need to adjust the current appropriately. This can be done via custom programming but there will be a delay before establishing a dedicated constant current/voltage again as the unit sources and measures and adjusts to what you need.
I would recommend using a dedicated electronic load unit capable of performing what you need, as these units are designed specifically for this application. See link below for an example unit that we at Keithley offer:
DC Electronic Loads | Tektronix