A tight-binding model comprising a hopping and an attractive interaction term was considered for high temperature superconductors. Explicit calculations on the effects of isotopic substitution of atoms and application of pressure on the transition temperatures were made in this work. Exact analytical expressions for the isotope-shift exponent (α) and pressure coefficient (γ_P) of transition temperature (T_C) considering the isotopic mass and pressure dependence of the hopping and attractive interaction strengths from a minimal model describing superconductivity were obtained. Theoretical predictions for α and γ_P with proper choice of parameters are found to be qualitatively consistent with the results of the experiments of high T_C oxides. The results depend on the band dispersion chosen.
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