Things appear to be heating up between the lagest health system and the second largest health system in the Pittsburgh health care market.  West Penn Allegheny Health System Inc. has filed and anti-trust lawsuit against the University of Pittsburgh Medical Center and Highmark Inc., the region’s largest insurer, claiming UPMC and Highmark have conspired to create a monopoly. Specifically, the lawsuit which was filed on April 21, 2009 U.S. District Court in Pittsburgh alleges that UPMC has refused to contract with smaller health insurance companies at reasonable rates and in exchange, highmark has agreed to pay UPMC at inflated rates.