DC9 First Officer reports a high speed rejected takeoff due to tire failure. The failed tires may have been under inflated prior to departure.

Narrative

Rejected takeoff at approx 110-120 KTS because of blown left side tires. Aircraft weight was 112;000 LBS with V1 speed of 144 KTS. After aircraft was stopped we cleared the runway and requested ARFF equipment to inspect the landing gear; brakes; wheels and tires for potential damage and or fire. It seemed to take much too long for the ARFF equipment to reach the aircraft. We had no initial indication from the flight deck of a fire and the flight attendants confirmed nothing abnormal in the cabin. When the fire trucks arrived they told us both left tires were gone and the right tires had just deflated. We came to the conclusion that the right tires deflated because of the fuse plugs melting from brakes overheating. After pushback the aircraft taxied; turned; and we used normal thrust to get to the runway. Initial takeoff roll up to 100 KTS was also normal with no yaw either left or right. During the exterior inspection all indications with the wheels; tires and brakes looked normal. The tug driver mentioned the tires looked low. we attributed this to the heavy weight of the aircraft because everything looked normal during the preflight. The Captain made the decision to continue based on the following; normal indications during exterior inspection; normal taxi; normal turning.