Development of AT(1) and AT(2) receptors in the ovine fetal brain.

This study determined the development of AT(1) and AT(2) receptors in the ovine fetal brain from preterm to term by utilizing Western blot for the receptor expression at the protein level, RT-PCR for the receptor mRNA, and immunostaining for the specific receptor immunoreactivity. The results demonstrated that AT(1) and AT(2) receptors developed in an increasing pattern from preterm to term gestational periods in the fetal sheep brain. Both AT(1) and AT(2) receptors have appeared in the major structures in the angiotensin-related central cardiovascular and body fluid controlling pathways at the 0.7 of the gestational age. Importantly, AT(1) receptors have been discovered in the supraoptic nuclei in the fetal hypothalamus, and in the lateral parabrachial nuclei and the ventrolateral medulla in the fetal hindbrain. This provides evidence of the anatomical existence of the angiotensin receptors in the brain areas that are critical for cardiovascular and fluid regulatory functions in utero. In addition, although the results demonstrated the predominance of AT(2) receptors in several regions such as the cerebellum in the ovine fetal brain, dominant occupation of AT(1) receptors in the hypothalamus have appeared early in the life of sheep animals before birth. Together, the data support the hypothesis that the central angiotensin receptors are well developed and established in the last third trimester of gestation. The brain receptors provide a pharmacological basis for the action of angiotensin in the maintenance of in utero fetal physiological functions, including cardiovascular and body fluid balance.