But companies with lower credit ratings, which make up a significant share of all big companies and include household names like Ford and Macy’s, could find the public markets more expensive. Yum Brands, which has a relatively low, or “junk,” credit rating, set its interest rate at 7.75 percent on the corporate bonds it sold Monday, nearly twice what it was paying a month ago.

Yum, which owns KFC and Taco Bell, expanded its offering to $600 million from the originally planned $500 million based on strong investor demand, but it may be among the lucky ones. Lower-rated companies play a huge role in the economy. Half of the 1,148 companies in the Russell 3000 stock index that have ratings are below investment grade, according to calculations based on data from CapitalIQ. Last year, these companies employed more than six million people and had revenue of $2.7 trillion.

To shore up their cash flow, hundreds of companies have chosen to draw from credit lines that banks agreed years ago to make available. Ford, which is still paying back a loan from the federal government made over a decade ago, last week tapped a $15 billion credit line; General Motors has said it would draw down $16 billion. Both have halted North American car production but are repurposing plants and workers to manufacture emergency batches of ventilators to undersupplied hospitals. Macy’s, which said it would furlough most employees, drew down a $1.5 billion credit line in March.

Even as Mr. Hernandez and other longtime Wall Street executives predict a seismic shift in the way corporations handle financing, their banks — which reduced their own dependency on borrowed money and bolstered their access to cash as a result of new regulations enacted after the financial crisis — continue to lend.

Between March 11 and March 18, bank lending surged by $243 billion to a total of $4.1 trillion, according to Mr. Foran, the analyst, who added that the increase occurred as companies tapped the credit they were already entitled to receive from banks as part of prior agreements. Consumer discretionary companies — coffee shop chains, shoemakers, car companies and other nonessential service providers — constituted by far the single-largest proportion of businesses borrowing money from banks, Autonomous noted in a recent report, a direct consequence of the sudden slide in their revenue from virus containment efforts. Industrial companies and real-estate firms, the firm reported, were the second- and third-largest users.

During the week ending March 18, the most recent week for which data is available, JPMorgan was the most active provider of financing, playing a leading role in an estimated $78 billion worth of credit facilities that were drawn down, according to figures tracked by Standard & Poor’s and Autonomous. Bank of America lent from an estimated $31 billion pool of credit. The companies appear to be putting the cash they draw down back in the banks.