The incidence of vasculitis is increased in female stroke-prone hypertensive rats compared to males

Abstract

Background: Vascular changes in hypertension share common characteristics with inflammatory wall injury. Since it is known that chronic inflammatory diseases are frequently more prevalent in females, this study tested the hypothesis that vasculitis would be more evident in female stroke-prone spontaneously hypertensive rats (SHRSP) than in males.

Methods: Arterial lesions were characterized in the gastrointestinal tract of necropsied SHRSP and normotensive Wistar-Kyoto rats (WKY). Systolic blood pressure was measured using the tail cuff method.

Results: Vasculitis was present in 54% of SHRSP (n=357). None of the WKY rats had the vascular disease (n=373). Arterial lesions were not evident in young SHRSP (1-1.5 months of age) before the development of high blood pressure. The earliest appearance of vasculitis in SHRSP was at ~8 months of age after full establishment of elevated arterial pressure. Systolic blood pressures during the maintained phase were greater than 200mmHg for SHRSP and less than 130mmHg for WKY rats (ages: 8-18 months). Within SHRSP, lesions were more common in females, in spite of higher mean systolic pressure found in males (both p<0.05). Of the female SHRSP, 70% (n=234) had severe micronodular vasculitis whereas 24% of male SHRSP showed lesions (age matched).

Conclusion: These observations indicate that in SHRSP: 1) inflammatory responses in arteries occur with greater incidence compared to WKY rats; 2) there is a relationship between incidence of vascular lesions and age, but not elevated arterial pressure; and 3) there is a higher incidence of vasculitic lesions in females compared to males.

Keywords: Vasculitis, Stroke-prone, SHR, WKY, Blood pressure, Hypertension