We perform a systematic investigation on the effects of Ba and La doping on the lattice and transport properties of Sr2IrO4, which is theoretically predicted to be a host compound of high-temperature superconductivity. We observe a drastic straightening of the Ir-O-Ir bond angle in the Ba-doped samples. The straightening of the bond angle is much weaker in the La-doped samples. It is found that the La doping leads to the introduction of electron-type charge carriers, while the charge carrier concentration does not change too much in the Ba-doped samples. As a result, both the resistivity and the magnetic moments decrease much faster in the La-doped samples, compared to those in the Ba-doped samples. The present results suggest that it is the charge carrier density rather than the Ir-O-Ir bond angle that dominates the magnetic and transport properties of the Sr2IrO4 system.