Morgan Stanley's profit beat Wall Street estimates in the second quarter as its traders cashed in on volatile markets, but shares fell since the market opening as its investment banking revenue shrank.

Shares of Goldman Sachs and Morgan Stanley fell Wednesday despite stronger-than-expected profit from the two big banks, as investors saw little reason to bid up equity prices further after gains in recent weeks.

Morgan Stanley's quarterly earnings of $2.13 a share on revenue of $16.8 billion exceeded analysts' estimates. Wall Street had forecast earnings per share of $1.98 and revenue of $16.1 billion. For the same period a year ago,