Importing a po file in hook update

mymodule.install

<?php

/**
 * Add pt translations
 */
function hook_update_7001() {
  $path = drupal_get_path('module', 'mymodule');
  $poFile = $path . '/translations/pt-pt-mymodule-7.x-1.0.po';
  $file = new stdClass;
  $file->uri = $poFile;
  $file->filename = basename($poFile); 
  _locale_import_po($file, 'pt-pt', LOCALE_IMPORT_OVERWRITE, 'default');
}