LOCAL RENIN-ANGIOTENSIN SYSTEM IN THE PINEAL-GLAND

Besides the classical endocrine renin-angiotensin system (RAS), a loca l RAS has been described also in the brain. We attempted to clarify th e existence of a local RAS in the pineal gland. Through the use of a r ibonuclease protection assay, it proved possible to detect the mRNA fo r angiotensinogen (AOGEN), for the angiotensin receptor type 1A (AT(1a )) and 1B (AT(1b)) and for the angiotensin-converting enzyme (ACE) in pineal glands from rats. Renin mRNA, however, could not be found by th is method. By in situ hybridization and immunocytochemistry, AOGEN mRN A was co-localized with the astrocyte marker glial fibrillary acidic p rotein. AT(1b) mRNA expression exceeded the expression of AT(1a) mRNA and was co-localized with the pinealocyte-specific tryptophan hydroxyl ase. Thus, in the mammalian pineal gland there is a local formation of the components of the RAS. The presence of angiotensin II receptors f urther substantiates a role for angiotensins and the pineal RAS in the physiology of this gland. (C) 1998 Elsevier Science B.V.