We propose a treatment of relaxation of nuclear polarization in electronically poor systems, such as heterostructures, based on the consideration of electrons as provisional spin holders but not as the spin bath. In this case the rate T1(-1) of decay of polarized states of nuclei is determined by the spin-orbital electron-phonon interaction and the conductivity of the electron gas (in open systems). The developed theory can be applied to experiments on nuclear magnetic relaxation in the quantum Hall effect regime.