Here’s what’s hot in the stock market today:  HCA Holdings (NYSE:HCA)and Silicon Laboratories (NASDAQ:SLAB) fell after reporting second quarter earnings, while Six Flags (NYSE:SIX) got a slight boost after reporting its own quarterly earnings. Raptor Pharmaceuticals (NASDAQ: RPTP) took a blow following clinical trials of a new drug for treating infant kidney development. Atrinsic (NASDAQ: ATRN), a lesser known Internet music company, saw increased interest after receiving good press over the weekend.

Here are the details on these high volume stocks:

HCA Holdings (NYSE:HCA) fell more than 15% after reporting second quarter earnings on Monday morning. Nearly 12 million shares were exchanged, more than 5 times the normal average of more than 2 million shares. The private hospital and health care facility operator reported net income of $229 million, EPS of 43-cents, which was a marked fall from the same period in 2010 when the holding company reported $293 million in income, or EPS of 67-cents per share. Shares were trading below $30 as of this writing.

Atrinsic (NASDAQ: ATRN), the parent company of Internet music website and former file-sharing service Kazaa, was up more than 80% on trading more than 10 times normal volume. Close to 2 million shares were exchanged by midday, when shares were trading just below $6. The boost came after a number of outlets spotlighted Atrinsic’s strong performance in recent months.

Silicon Laboratories (NASDAQ:SLAB) fell almost 12% after lowering expectations for its third quarter. The analog chip and integrated circuit manufacturer will report earnings at market close on Monday when it will report second quarter EPS of 48-cents per share. Analysts were predicting EPS of 46-cents for the company. Unfortunately the company expects revenue to fall between 5 and 10% in the third quarter due to low demand for its TV tuner products. More than 2 million shares were exchanged, compared to the average of close to 500,000. Shares were trading around $37 by midday.

Six Flags (NYSE:SIX), the amusement park operator, rose more than 1% on close to double normal trading volume. Nearly 1 million shares were exchanged by midday. Shares took a significant dip in early trading before recovering after the company reported its second quarter earnings. Revenue totaled $339 million, a 5% increase over the same period in 2010. Shares were trading just below $40 as of this writing.

Raptor Pharmaceuticals (NASDAQ:RPTP) fell 22% on four-times normal trading volume. The early development drug company announced on Monday that it met the primary endpoint in its Phase 3 clinical trial for a new drug for treating nephropathic cystinosis, a condition where infants’ kidneys fail to grow properly. Almost 3 million shares in the company were exchanged by midday. Shares were trading above $5.

As of this writing, Anthony John Agnello did not own a position in any of the stocks named here. Follow him on Twitter at @ajohnagnello and become a fan of InvestorPlace on Facebook.