WASHINGTON — House Republicans summoned a half-dozen health insurance executives to a hearing Wednesday envisioned as another forum for criticism of the Affordable Care Act. But insurers refused to go along with the plan, and surprised Republican critics of the law by undercutting some of their arguments against it.

Insurers, appearing before a panel of the Energy and Commerce Committee, testified that the law had not led to a government takeover of their industry, as some Republicans had predicted. Indeed, several insurers said their stock prices had increased in the last few years.

The executives also declined to endorse Republican predictions of a sharp increase in insurance premiums next year, saying they did not have enough data or experience to forecast prices. And they said they were already receiving federal subsidy payments intended to make insurance more affordable for low- and middle-income people.

Representative Michael C. Burgess, Republican of Texas, sounded a bit disappointed at the end of the hearing. He marveled at the subdued testimony and complained that no one at the witness table “wanted to be forthcoming.”