Induction of immunoreactive prostaglandin H synthases 1 and 2 and fos in response to cerebral hypoperfusion in late-gestation fetal sheep.

OBJECTIVE: The goal of the present study was to localize and quantify immunoreactive prostaglandin H synthase 1 (PGHS-1), PGHS-2, and Fos expression by immunohistochemistry in the fetal brain 30 minutes and 2 hours after the onset of a 10-minute period of cerebral hypoperfusion in barodenervated and chemodenervated fetal sheep.

METHODS: Fetal sheep of known gestational age were studied intact or sinoaortic denervated. Fetuses were sacrificed and tissues recovered for immunohistochemistry or real-time polymerase chain reaction measurements of protein and mRNA, respectively. Some fetuses were subjected to brachiocephalic occlusion, produced by inflation of an extravascular balloon occluder around the brachiocephalic artery. Immunohistochemistry results were quantified using image analysis, and mRNA was quantified by estimation of cycle threshold in generation of PGHS-1 or PGHS-2 amplicons.

RESULTS: Sinoaortic denervation by itself did not alter the abundance of PGHS-1 or PGHS-2 protein in any brain region, although the denervation did reduce the abundance of PGHS-1 mRNA in hypothalamus. We assessed PGHS-1, PGHS-2, and Fos immunoreactive protein abundance by image analysis of histologic sections stained for the respective proteins using immunohistochemistry. Cerebral hypoperfusion increased the intensity of staining of immunoreactive PGHS-1, PGHS-2, and Fos in the anterior pituitary, hippocampus, and cerebellum. In the cerebral microvasculature, the intensity of PGHS-1 and Fos was significantly greater, and in the cerebral cortex, the intensity of PGHS-2 was significantly greater. Changes in the amount of immunostaining in the nucleus of tractus solitarius and paraventricular nucleus were not statistically significant.

CONCLUSION: Cerebral hypoperfusion altered the expression and distribution of prostaglandin biosynthetic enzymes in ovine fetal brain by a mechanism that is independent of baroreceptor and chemoreceptor afferent activity.