One-hour lead treatment enhances hyperthermia-induced thrombosis in pial microvessels of the mouse

Thrombosis in pial microvessels was studied in adult male mice treated with lead (Pb) 60-min prior to applying local hyperthermia. Lead acetate was dissolved in a 5% glucose solution, vehicle. Four groups were used (10 mice each), 3 received Pb at levels of 0.1, 0.5 and 1 mg/kg (i.p.) and the control received vehicle. Microsurgery was performed on anesthetized animals (urethane, 1-2 mg/g, i.p.) and microvessels (30-50 μm) were monitored by intravital video-microscopy. A glass well was affixed on the head, where artificial cerebrospinal fluid (ACSF) was delivered and drained. A temp-controlled system was used in raising ACSF temp first to 37°C for a 30-min stabilization period, then to 45°C for 25 min, while core body temp remained constant at 37°C. Both passing emboli and visible thrombi were observed when ACSF temp reached 45°C. Compared to control, the 3 levels of Pb-treatment accelerated thrombo-embolism (3.1±1.5, 4.9±3.3 and 2.9±1.5, respectively vs 17.9±7.6 min; P<0.01). Arteriolar constriction was evident in all groups, but venular diameter was not changed. Patent arterioles (out of 10) at end of procedure for Pb-treated groups were: 7, 6 and 8 vs 9 for control. Thus, 1-h exposure to Pb could expedite thrombo-embolism in mouse pial microvessels under the applied local hyperthermic condition.