The effect of oestrogen on the development of arteriovenous fistulae induced by venous hypertension in rats.

Abstract

Dural arteriovenous fistulae (AVF) represent abnormal communication between the meningeal arteries and the dural sinuses. Clinically, this condition appears more frequently in post-menopausal and pregnant 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 by surgically creating a carotid-jugular shunt in male rats, which then induces venous hypertension, spontaneous arteriovenous fistulae can result. To examine the specific role that oestrogen may have in the development of AVF induced by venous hypertension, we performed the following experimental procedure. Ninety-four Sprague-Dawley female rats (250-300 grams in weight) were randomly assigned to four different groups. Group 1 (n = 20): control (bilateral ovariectomy only). Group 2 (n = 19): bilateral ovariectomy and implantation of the oestrogen pellet (17-beta oestradiol 0.75 mg/pellet, 60 days release). Group 3 (n = 17): bilateral ovariectomy and venous hypertension (left carotid-jugular shunt with proximal jugular vein occlusion). Group 4 (n = 38): bilateral ovariectomy and oestrogen pellet implantation and 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 shunt to examine for any newly developed AVF. No newly developed 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%) venous 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 hypertensive rats. In this experimental study, ovariectomy with or without oestrogen did not affect the development of spontaneous AVF induced by venous hypertension.