Nucleosynthesis reaction networks leading to p-nuclei involve a combination of different types of photodisintegration and capture reactions, as well as β+ decays or electron captures. Photodisintegration reactions involving α particles present a particular interest as they serve as branching points of the reaction networks. The cross sections of these reactions depend crucially on the α-nucleus interaction. The α optical model potential (AOMP) is determined mostly by means of experimental differential elastic scattering distributions. Several previous studies have focused on the case of 144Sm, an intriguing p-nucleus that is semi-magic with 82 neutrons. This work presents new experimental data on α elastic and inelastic scattering on 148Sm, its closest stable isotope. Isotopic effects on the description of the AOMP are studied, as well as their consequences on the prediction of α-induced reaction cross sections at astrophysical energies. It is shown that the isotopic ratio for (α, γ) cross sections can be multiplied up to a factor of two when these effects are included.