Silica attenuates hypertension in Lyon hypertensive rats.
OBJECTIVE
Evidence has been provided suggesting an association between hypertension and immune dysfunction in Lyon hypertensive (LH) rats. In the present study, we investigated the possible role played by macrophages in LH rats by examining the blood pressure consequences of the chronic administration of silica, a selective toxin to macrophages in vivo.


METHODS
LH and Lyon low blood pressure (LL) male rats were treated with silica at a dose of 200 mg/kg per week intraperitoneally from age 4-10 weeks. Controls received saline. Blood pressure was measured by plethysmography from age 6-10 weeks and an intra-arterial recording was performed in 11-week-old, freely moving rats.


RESULTS
Treatment with silica did not modify blood pressure in LL rats at any age. In contrast, 1 week after the beginning of the treatment, the blood pressure of silica-treated LH rats was lower than that of untreated LH rats. As shown by intra-arterial recording, the effect persisted 1 week after cessation of the treatment. In addition, silica decreased the left ventricle weight in LH but not in LL rats.


CONCLUSIONS
The present results show that weekly administration of silica in young LH rats attenuates the development of hypertension and of left ventricular hypertrophy, a finding which suggests that macrophage-mediated immune reactions may play a pathogenic role in LH rats.
Department of Physiology and Clinical Pharmacology, Lyon, France.
A
A
Bataillard
C
C
Renaudin
J
J
Sassard
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006973:Hypertension / Q000188:drug therapy* / Q000276:immunology / Q000503:physiopathology; D017379:Hypertrophy, Left Ventricular / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D007274:Injections, Intraperitoneal; D008264:Macrophages / Q000187:drug effects*; D008297:Male; D009929:Organ Size; D010991:Plethysmography; D051381:Rats; D012822:Silicon Dioxide / Q000633:toxicity*
D012822:Silicon Dioxide