抄録
Using spontaneously hypertensive rats with different degrees of hypertension, the influence of the duration of hypertension on platelets was examined through changes in platelet serotonin contents. Their blood pressure was in the order of m-SHRSP>SHRSP>SHR>WKY. Serotonin content in normotensive WKY platelets was maintained in the range of 0.715±0.048 (17) n mole/108 cells through ages (5-50 weeks) in both sexes. In contrast, a significant decrease has begun to be observed in male m-SHRSP at 18 weeks of age, in female m-SHRSP and male SHRSP at 22 weeks, and in female SHRSP at 32 weeks respectively, compared with age-and sex-matched WKY. The content in SHR of both sexes was unaltered upto 36 weeks of age. Time of the appearance of these exhausted platelets coincided with the reported time of scan electron microscopic observation of vascular injuries in each strain of rats.
Then, stroke was induced in SHRSP by 1% NaCl loading starting at 10 weeks of age. About 2/3 of them showed stroke signs with concomitant decrease in body weight, and increase in urinary volume and protein within 2-3 weeks. They were killed in 3 weeks and cerebral lesion was confirmed by autopsy. Platelet counts in stroke group was reduced to 36%, and thrombin-induced aggregation to 66% of those of healthy group. ADP and serotonin contents in platelets diminished by 45 and by 65% respectively due to stroke while plasma TBARS in stroke group was two fold of healthy group. There was a singificant inverse correlation between platelet serotonin content and plasma TBARS.
It is concluded that long duration of hypertension causes platelets degranulated and exhausted due to in vivo activation of platelets at injured arteries, thus the changes of platelet contents could be prediction of vascular injuries.
