Stocks briefly broke into positive territory this afternoon after spending most of the trading day in the red. Yet they sold off into the close to end the session slightly lower. The S&P 500 (SNPINDEX:^GSPC) lost 0.04% while the Dow Jones Industrial Average (DJINDICES:^DJI) lost 0.14%.

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In economic news, the government announced this morning that GDP growth slowed significantly, rising by 1.5% in the third quarter, according to a preliminary estimate, compared to the second quarter's 3.9% gain. Consumer spending, state and local government spending, and real estate investment all contributed to the positive result. Rising inventory levels and higher imports detracted from growth.

Meanwhile, Pfizer (NYSE: PFE) pulled the Dow lower today on rumors of a massive merger in the drug industry and Sherwin Williams' (NYSE: SHW) stock made a big move after the company demonstrated just how profitable the paint business can be.

Pfizer looks to change addresses
Pfizer was the second largest percentage loser on the Dow today, falling 2% on news that it was considering acquiring rival Allergan. With a market capitalization of over $100 billion, this would easily be the biggest M&A deal of the year if it goes through. Coupled with Pfizer's $220 billion market cap, an Allergan merger would create a truly massive global drug giant.

Among the possible benefits for Pfizer here would be a stronger patent-protected drug portfolio, as it would bring hit products like wrinkle-reducer Botox under its control. Any deal would also have important tax implications, since Allergan is headquartered in Ireland, which has a lower corporate tax rate than the United States does. While not commenting on the rumored deal itself, Pfizer CEO Ian Read told The Wall Street Journal today that his company was operating at a "tremendous disadvantage" against foreign companies with lower tax burdens . Merging with one of those foreign companies might help change that dynamic.

Officially, Pfizer has only confirmed that it is "in preliminary friendly discussions" with Allergan over a potential transaction. "No agreement has been reached, and there can be no certainty that these discussions will lead to a transaction," the company warned investors in a press release. Until any details are announced, shareholders can only speculate about what's going on behind the scenes in Pfizer's and Allergen's boardrooms right now .

Sherwin Williams posts record profitability
Paint specialist Sherwin Williams saw its stock jump 4% higher today after the company posted surprisingly strong third-quarter results. The $3.97 per share of profit it announced this morning easily beat Wall Street estimates as quarterly revenue held flat at $3.15 billion. Adjusted for currency swings, Sherwin Williams' sales growth was a healthy 4 %.

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Image source: Sherwin Williams.

The paint retailer's improving profitability was the star of this quarterly report. Gross profit spiked higher by over three percentage points, to 49.9% of sales. Its army of paint stores produced 17% higher earnings on just a 4% sales improvement. As a result, net income reached 11.9% of sales, which set a new all-time high for the 149-year-old company. "it is gratifying to report another quarter of sales increases and earnings-per-share growth," CEO Christopher Conner said in a press release.

Management expects the positive profit trend to continue into next quarter. Sherwin Williams raised its earnings guidance and now targets producing as much as $11 per share of earnings for the full year, up 25% over last year's $8.78 per share result.

That leaves the stock valued at roughly 23 times this year's earnings, which is still below the 26 P/E it has attracted through most of 2015.

Demitrios Kalogeropoulos owns shares of Sherwin-Williams. The Motley Fool recommends Sherwin-Williams. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.