Health insurer Aetna Inc. said late Tuesday its second-quarter profit rose 42 percent, as the percentage of premiums the company spent on medical care fell versus a year ago. The insurer said it earned $491 million, or $1.14 a share, in the three months ended June 30. That compares with net income of $346.6 million, or 77 cents a share, in the same period last year. Aetna earned $450.2 million, or $1.05 a share, excluding one-time items. The company also raised its forecast for its 2010 operating earnings. Total second-quarter revenue fell to $8.54 billion from $8.67 billion, in part due to a drop in premium revenue from lower commercial insured membership.