Effect of male sex and obesity on platelet arachidonic acid in spontaneous hypertensive heart failure rats.

Sexual dimorphism is observed in the progression to congestive heart failure and, ultimately, in longevity in spontaneously hypertensive heart failure (SHHF) rats. As platelet activation may impact development of cardiovascular diseases, we studied the effects of obesity and sex on platelet polyunsaturated fatty acid (PUFA) profile and its relationship to platelet aggregation in 6-month-old SHHF rats. After a 24-hr fast, blood was obtained for measurement of platelet phospholipid omega-6 (n-6) and omega-3 (n-3) PUFA. Collagen-induced platelet aggregation was measured by whole-blood impedance aggregometry. Obese male (OM) SHHF had significantly more platelet arachidonic acid (AA) and total n-6 PUFA than lean males (LMs), lean females (LFs), or obese females (OFs). Platelet aggregation was enhanced in males compared to females, with OMs by 45% compared to OFs and with LMs by 28% compared to LFs. Though no difference was found between OFs and LFs, platelet aggregation was increased in OMs by 20% compared to LMs. Though not significantly different, lag time to initiate platelet aggregation tended to be shortest in OMs and then, in increasing duration, LMs, LFs, and OFs, suggesting that platelets from male rats were quicker to aggregate than those from females. Platelet aggregation was correlated with platelet AA and total n-6 PUFA content. There was no relationship between n-3 PUFA and platelet aggregation. In SHHF rats, elevated AA and n-6 PUFA levels in platelets are associated with enhanced platelet aggregation. This relationship is potentiated by obesity and male sex.