Spin-lattice relaxation of quadrupole nuclei in ideal pure nonconducting solids is known to be realized due to modulation of crystalline electric field gradients by thermal phonons [1]. This “lattice” quadrupole relaxation has a specific temperature dependence of its velocity [2]. Another contribution to spin-lattice relaxation can occur in real solids owing to paramagnetic impurities. However, even in pure materials, which do not comprise paramagnetic impurities, there can be an additional relaxation channel associated with intrinsic structural point defects, such as electron centers. Nuclear spin relaxation in semi-insulator undopped gallium arsenide crystals is an example of such a case [3]. Electron centers, which are strongly coupled to the phonon system, are also linked to neighbor nuclei via hyperfine magnetic and electric quadrupole interactions [4]. It leads to fast nuclear spin relaxation near the electron centers, which extends over the whole crystal volume due to spin diffusion. The contribution of electron centers to nuclear spin-lattice relaxation can be found using a method of measuring the spin-lattice relaxation rate under continuous magnetic saturation of the nuclear spin system [5]. The magnitude of the contribution caused by electron centers and its variation with temperature is mainly driven by the nature of the interaction between nuclei and electron centers. Recently, it was shown [3] for the ⁷¹Ga and ⁶⁹Ga isotopes in a semi-insulator GaAs crystal that the contribution to spin relaxation due to electron centers is dominated by quadrupole interaction while the impact of the hyperfine magnetic interaction is not noticeable. Another scenario can be expected for the ⁷⁵As nuclear spin system since the magnetic hyperfine interaction of electron centers with arsenic nuclei is more effective than with gallium isotopes as was demonstrated for most numerous EL2 centers [6]. Here we present NMR studies of different contributions to ⁷⁵As spin-lattice relaxation in the same semi-insulator GaAs crystal, which was used in [3]. The results for gallium and arsenic nuclei will be compared.