Obstructive sleep apnoea patients have increased platelet activity (Sanner et al. 2000). Acute (Li & Guo, 1996) and chronic continuous hypoxia (Nakanishi et al. 1997) are known to affect platelet function and number but the effects of chronic intermittent asphyxia (CIA), as occurs in obstructive sleep apnoea, are not known. In this study, we test the hypothesis that CIA causes changes in platelet function and number.
Wistar rats (CIA, n = 13) were exposed to alternating periods of normoxia and asphyxia twice a minute, 8 hours per day for 3 weeks. Controls (C, n = 16) were given air at the same flow rates as the CIA group. After 3 weeks, rats were anaesthetized (pentobarbitone, 60 mg kg-1 I.P.), artificially ventilated and thoracotomized. Blood was withdrawn from the left ventricle and analysed for platelet count, platelet activation (CD62p expression), response to low dose ADP (loss of single platelets) and closure time in the PFA 100 test, a test of blood coagulation. Animals were killed by anaesthetic overdose. All procedures were performed in accordance with national legislation under the Cruelty to Animals Act, 1876 and EU Directive 86/609/EC. Values are expressed as means ± S.D. and compared using ANOVA or the Mann-Whitney U test, (P < 0.05 taken as significant) where appropriate.
After the 3-week treatment, there was a significant difference in body weight between the two groups. There was no difference in platelet count between the two groups (C: 880.4 ± 80.3; CIA: 914.1 ± 127.1 X 103 µl-1) or in the reduction in count in response to ADP (reduced to 212.5 ± 193.5 vs. 190.7 ± 129.3 X 103 µl-1, C vs. CIA). There was no difference in the PFA closure time (C: 86.2 ± 27.4; CIA: 81.7 ± 20.1 s) or in the % of platelets positive for CD62 (C: 7.4 ± 9.2; CIA: 5.7 ± 3.1 %).
In conclusion, unlike chronic continuous hypoxia (Nakanishi et al. 1997), CIA did not cause a reduction in platelet number and had no effect on platelet activation. These results do not support a role for CIA in the changes in platelet function observed in obstructive sleep apnoea.
This work was supported by the Royal College of Surgeons in Ireland.