Eastman Kodak has been struggling to reinvent itself for decades. So when Antonio M. Perez, the chief executive, announced in July that he was confident that Kodak could transform itself into a profitable and sustainable digital company by 2012, many investors were skeptical.

Kodak’s unexpected decision to tap its credit line for $160 million last Friday reinforced concerns about the viability of the company’s turnaround strategy, which relies on selling inkjet printers, commercial printing and company patents, and on Monday, its shares lost a quarter of their value, closing at $1.74.

Kodak’s stock price has declined nearly 70 percent since the start of the year.

“We didn’t anticipate them having to use it in the third quarter going into the fourth quarter,” said Shannon Cross, of Cross Research in Livingston, N.J. “It just shows that the core business continues to burn cash.”

Image Kodak film headed for packaging at the factory. The company invented the digital camera, but rivals overtook that market. Credit... David Duprey/Associated Press

Chris Whitmore, an analyst at Deutsche Bank Securities, said that Kodak had $957 million in cash at the end of its most recent quarter, and it announced that it would have as much as $1.7 billion by the end of the year. As a result, he said, investors were expecting Kodak to be selling assets to generate cash, not borrowing.