Vessel Injury, Thrombosis And Platelet Survival

In vascular disease it is unclear whether shortened platelet survival (PS) primarily reflects vessel injury or thrombosis. In rabbits and rats (4-6 animals per group) we examined the relations among experimental thrombosis, vessel wall injury and platelet survival and turnover. In rabbits preinjected with autologous 51Cr-platelets, a 20 cm intra-aortic-catheter in situ for 4 days resulted in a thrombus (mean wt. 23.4 mg). A significant amount of 51Cr was associated with the aorta (0.53 ± 0.13% of total 51cr circulating before surgery). PS was reduced (no catheter 62.4 ± 8.8; catheter 37.0 ± 5.6 hr, p<0.05). With a 10 cm catheter, thrombus wt. was similar (mean 24.0 mg). 51cr associated with the aorta was 0.25% ± 0.06% but PS was unaffected (no catheter 55.4 ± 6.8; catheter 53.8 ± 3.6 hr). In other experiments, sham-operated controls were compared with rabbits with 20 cm catheters. Mean thrombus wt. was 30.2 mg and 0.53 ± 0.11% of the 51cr was associated with the aorta. PS was significantly shorter in the catheter rabbits (36.7 ± 2.8 hr) vs sham-operated controls (68.0 ± 10.4 hr, pp<0.02); platelet turnover was significantly increased (14,500 ± 970 vs 9,950 ± 1,020 per mm3/hr, pp<0.01). Three groups of rats preinjected with homologous 51Icr- platelets were studied: a) sham-operated, b) aortic catheter 7.5 cm, c) aortic catheter 12.5 cm. No macroscopic thrombi were observed at any time during the 4 days that catheters were in situ. Mean PS was: a) 97.7 ± 2.4, b) 88.5 ± 2.6 and c) 63.7 ± 5.1 hr (pp<0.001, a vs c). Platelet turnover was a) 8,400 ± 720, b) 8,900 ± 870 and c) 11,000 ± 1,150 per mm3/hr. 51Cr associated with the aortae was a) 0.004 ± 0.001, b) 0.013 ± 0.006 and c) 0.027 ± 0.011% of total (pp<0.05, a vs c). Thus in rats, catheters shorten PS without thrombosis. Therefore, with catheter-induced vessel injury PS appears directly related to length of catheter and extent of injury. Shortened PS can occur without thrombus formation and thrombus formation can occur without changing PS or platelet turnover.