THE EFFECT OF ESTROGEN ON THE DEVELOPMENT OF ARTERIOVENOUS-FISTULAS INDUCED BY VENOUS HYPERTENSION IN RATS

Purpose: Dural arteriovenous fistulae (AVF) represent abnormal communi cation between the meningeal arteries and the dural sinuses. Clinicall y, this condition appears more frequently in postmenopausal and pregna nt women than in the general population. Oestrogen is believed to play an important role in the development of dural AVF; however, its exact role has not been clearly defined. We have previously reported that b y surgically creating a carotid-jugular shunt in male rats, which then induces venous hypertension, spontaneous arteriovenous fistulae can r esult. To examine the specific role that oestrogen may have in the dev elopment of AVF induced by venous hypertension, we performed the follo wing experimental procedure. Materials and methods: Ninety-four Spragu e-Dawley female rats (250-300 grams in weight) were randomly assigned to four different groups. Group 1 (n = 20): control (bilateral ovariec tomy only). Group 2 (n = 19): bilateral ovariectomy and implantation o f the oestrogen pellet (17-B oestradiol 0.75 mg/pellet, 60 days releas e). Group 3 (n = 17): bilateral ovariectomy and venous hypertension (l eft carotid-jugular shunt with proximal jugular vein occlusion). Group 4 (n = 38): bilateral ovariectomy and oestrogen pellet implantation a nd venous hypertension. All of the groups were examined by angiography 60 days after treatment. In Groups 1 and 2, bilateral common carotid angiography was performed via a transfemoral route. In Groups 3 and 4, angiography was done after surgical ligation of the carotid-jugular s hunt to examine for any newly developed AVF. Results: No newly develop ed AVF were found in either Groups 1, 2, or 3. In Group 4, 2 rats (5.3 %) developed newly formed AVF which occurred in the nose and neck. Our previous study demonstrated that AVF appeared in 3 of 22 (13.6%) veno us hypertensive male rats. Therefore, no statistical difference in the appearance rate of newly formed AVF was found among groups 1, 2, 3 or 4 and between our previously reported group of male venous hypertensi ve rats. Conclusion: In this experimental study, ovariectomy with or w ithout oestrogen did not affect the development of spontaneous AVF ind uced by venous hypertension.