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April 29 (Reuters) - Managed care company HealthSpring Inc (HS.N: Quote, Profile, Research) posted a 50 percent rise in quarterly profit helped by strong growth in Medicare premium revenue, and raised its 2008 earnings view, sending its shares up 13 percent.

The company, which provides Medicare-related health plans, posted net income of $21.1 million, or 37 cents per share, for the first quarter, compared with $14.1 million, or 25 cents per share, a year earlier.

Total revenue rose 55 percent to $552.6 million. Medicare premium revenue increased 62 percent to $538.6 million. Medicare is the U.S. government's health insurance program for people who are 65 years of age or older.

Analysts were expecting the company to earn 24 cents a share, before special items, on revenue of $513 million, according to Reuters Estimates.

The first-quarter results included the operations of HealthSpring's Leon Medical Center Health Plans unit, which it acquired last October.

For 2008, Healthspring expects to earn $1.85 to $2.00 a share. In March, the company had said it expects earnings of $1.75 to $1.90 a share.

The company still expects 2008 total revenue of $2 billion to $2.2 billion, with almost all of the total revenue for the year coming from the Medicare business.

Analysts were expecting 2008 earnings of $1.78 a share on revenue of $2.09 billion.

Shares of the Franklin, Tennessee-based company were up $2 in trading after the bell. They closed at $15.36 Tuesday on the New York Stock Exchange. (Reporting by Esha Dey in Bangalore; Editing by Pratish Narayanan)