DaVita Inc. the nation’s largest operator of dialysis clinics, on Monday said it would buy HealthCare Partners, Los Angeles County’s largest operator of physician practices, in a deal valued at more than $4.4 billion.

The purchase price includes of $3.66 billion in cash and about 9.38 million shares of DaVita stock, in addition to performance bonuses. Privately held HealthCare Partners is based in Torrance and operates physician practices and networks in Southern California, Central Florida and Southern Nevada. Its revenues were about $2.4 billion last year.

DaVita, which moved its corporate headquarters from El Segundo to Denver in 2009, said the deal expands its business model, enables it to cut costs and be more competitive under national health care reform. Government reimbursement will increasingly favor providers that are part of accountable care organizations offering better integration among physician practices, hospitals and other care facilities.

“This combination will create a unique patient- and physician-focused organization,” said DaVita Chief Executive Kent Thiry in a statement. “We believe our combined enterprise will offer new and exciting levels of clinical quality, service, and consumer/taxpayer savings.”

The acquisition is subject to regulatory review and the approval of HealthCare Partners’ owners. HealthCare Partners will operate as a separate subsidiary of DaVita. The current HealthCare Partners senior management team has committed to stay, the companies said, with Chief Executive Robert Margolis joining DaVita’s board of directors and serving as co-chairman with Thiry.

DaVita shares were up $3.75, or 4.6 percent, to $84.56 in midday trading on the New York Stock Exchange.