  Oxygen isotope effects on the transport properties have been studied in
high-quality epitaxial thin films of La_{0.75}Ca_{0.25}MnO_{3} and
Nd_{0.7}Sr_{0.3}MnO_{3}. In the paramagnetic state, the resistivity can be well
fitted by \rho (T) = (A/\sqrt{T})\exp(E_{\rho}/k_{B}T) with the parameters A
and E_{a} depending strongly on the oxygen isotope mass. The resistivity below
80 K almost perfectly follows \rho = \rho_{o}+
B\omega_{s}/\sinh^{2}(\hbar\omega_{s}/2k_{B}T) with \hbar\omega_{s}/k_{B} \sim
100 K. Both \rho_{o} and B increase by about 15(3)% upon raplacing $^{16}$O by
$^{18}$O. The results provide quantitative constraints on the basic physics of
manganites.
