MOSCOW — American and European sanctions rattled Russia’s economy on Friday, with Moscow’s stock indexes opening sharply lower, rating agencies threatening to reduce the country’s creditworthiness, and hints of trepidation coming from Russia’s tycoons as they concluded an annual conference here.

But if the aim of the sanctions is to put economic pressure on the wealthy allies crucial to President Vladimir V. Putin’s continued grip on power, there were few signs they would succeed, largely because those targeted were among the new generations of oligarchs who owe their fortunes and loyalties to Mr. Putin.

And even though Russia has become more integrated in the global economy, those who were not targeted — other billionaires and millionaires who have prospered in the Russia that emerged under Mr. Putin’s rule — have not shown signs of breaking ranks, either, since the prospects of sanctions first arose.

One of those facing sanctions, Vladimir I. Yakunin, a close adviser and the head of Russian Railways, said in an interview before President Obama’s announcement of expanded penalties on Thursday that Mr. Putin was “a very difficult person” when he felt under pressure to bend to the demands of others and would not yield to international condemnation.