Max Voltage of Electrical Stimulator for Cardiac Tissue Bioreactor
Your stimulator is a constant-current device, which means it will vary voltage automatically in order to keep the current at a set value. The maximal voltage it can achieve depends entirely on the internal design -- if it really claims 105 milliamps into 1000 ohm load, this means it can output up 100 volts, which means it must have some sort of voltage step-up circuit inside.

If your resistance will be constant, then you set the current using Ohm's law: current = voltage / resistance, for example for 12 volts and 1900 ohms, you set 6.3 milliamperes. The only problem is that if resistance changes (for example due to changed concentration of ions), so will voltage. For the previous case, if your media has less ions and resistance is now 950 ohms, the stimulator will now output 24 volts to try and maintain the same 6.3 milliamperes current. Thus, if you really care about fixed voltage, get a stimulator where you can set the voltage directly.