(Corrects second bullet to clarify that rising asset prices may hurt growth, not profits. Also drops reference to tepid 2012 from headline as the mean forecast calls for a 24 percent year-over-year growth. The error in the headline first appeared in Update 1)

- Leasing company GATX Corp posted market-beating quarterly results on higher demand and pricing for its railcars, and expects continued improvement in its rail segment's results this year.

However, growth beyond its existing committed railcar orders will become more challenging as asset prices rise, the company said in a post-earnings call. Backlog in tank car market is still over 12 to 15 months, it said.

GATX, valued at about $2 billion, forecast a 2012 profit of $2.40 to $2.60 a share. Analysts, on average, were expecting earnings of $2.55 a share, according to Thomson Reuters

I/B/E/S.

The company -- which also leases out equipment to marine and other industrial customers -- expects to raise rates on the 20,000 railcars that are scheduled for renewal in North America this year, Chief Executive Brian Kenney said in a statement.

The rail segment, which handles tank, freight car, and locomotive leasing, contributed about 71 percent to Chicago-based GATX's revenue in the fourth quarter.

For the quarter ended December 31., GATX's net profit rose to $31.6 million, or 67 cents a share, from $19.5 million, or 42 cents a share, last year.

Analysts had expected earnings of 55 cents a share.

Revenue rose 14 percent to $350.4 million, higher than the $328.3 million anticipated by analysts.

Shares of the company rose about a percent to a more-than-three-year high of $45.50 Thursday morning on the New York Stock Exchange, but were down about a percent at $44.47.

The stock has gained about 25 percent since GATX reported third-quarter results last October.

(Reporting by Ritika Rai in Bangalore; Editing by Sreejiraj Eluvangal, Unnikrishnan Nair)