We present results on spin-polarized electron transport from a ferromagnet to a two-dimensional electron gas system (2DEG). The investigated device consists of an injector and a collector contact made from ferromagnetic permalloy thin films with different coercive fields. That allows parallel or antiparallel magnetization of the contacts in different applied magnetic fields. The conducting medium is a 2DEG formed in an AlSb/InAs quantum well. Data from this device suggest that its resistance is controlled by two different types of spin-valve effect: the first is due to the ferromagnet-semiconductor contact resistance, determined by the zero-field spin-splitting in InAs, and the second is due to the propagation of electrons with a spin imbalance through the 2DEG without spin-scattering.