By Kimberly Leonard | Staff Writer Sept. 8, 2016, at 3:26 p.m. | USNEWS.com

Five Democratic Senators sent a letter to Aetna’s chairman and CEO Thursday saying that they were troubled by the possibility that the company was pulling its participation from health insurance exchanges in retaliation for a Department of Justice lawsuit blocking its proposed multibillion-dollar merger.

Senators including Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt., urged Aetna CEO Mark Bertolini to “answer both to your shareholders and to the thousands of Americans who trusted Aetna with their health coverage.” Among their questions: how much money the company would lose if its proposed $37 merger with another health insurance giant, Humana, doesn’t go forward.

In August, Aetna announced it would be significantly reducing its participation in exchanges created by the Affordable Care Act, President Barack Obama’s signature health care law, which allow some Americans to shop and buy health coverage at a tax-subsized rate. More than 11 million Americans receive coverage this way, and moves like Aetna’s mean fewer insurance options for patients, resulting in higher costs and limiting access to providers. In some areas, Aetna’s decision means patients will have only one health insurance option on their exchanges.

At the time, the company said it made its decision to scale back based on steep financial losses, but Warren soon accused Aetna of having other motives.

An Aetna letter to the Justice Department was made public soon after, and its contents suggested Warren’s assertions – that Aetna was responding to the blocked merger – were correct. In an email to U.S. News, however, Aetna attached a letter sent to the company by the Justice Department, which specifically prompted the company to explain the effect that a lawsuit would have on its business and on its exchange participation in particular.

Aetna noted in an email that several health insurance companies had left the exchanges.

“Singling Aetna out may be politically convenient during election season, but this letter ignores realities and takes the focus away from needed reforms,” an Aetna spokesperson said in an email. “The ACA is not sustainable without bipartisan action that improves access, affordability and quality of care for consumers.”

The senators – who included Sherrod Brown, D-Ohio, Ed Markey, D-Mass., and Bill Nelson, D-Fl. – noted Thursday that Aetna initially appeared to support Obamacare’s exchanges, and had even talked about expanding to more states for 2017.

They also pointed out a statement during an earnings call in April in which the company stated that the exchanges were a “good investment” and that Aetna was dedicated to “working constructively with the administration and lawmakers.”

The Senators gave Aetna until Sept. 15 to respond to their questions so they could “better understand Aetna’s questionable decisions.” They asked how Aetna determined which states to withdraw from and why its deal included a $1 billion fee that would be incurred if the merger didn’t move forward.

“Because the risks of the merger were obvious from the beginning, these actions are both inexplicable and irresponsible,” the senators wrote.