October - December 2006, Volume 2, Issue 4

Badiu C, Moller M, Coculescu M

Morphological evidence for a intrinsic angiotensin system in the bovine pineal gland

Acta Endo (Buc) 2006, 2 (4): 389-401
doi: 10.4183/aeb.2006.389

accepted. Such an intrinsec system of the pineal gland was revealed by Rumanian scientists, which found a high renin like biological activity in the rat pineal, after nephrectomy, and also de novo production of isorenin by the monolayer cultured pineal cells; angiotensin I (A I) - immunoreactivity -was also found in the rat pineal at much higher concentration than in the brain structures. In this paper we add morphological evidences regarding components of the RAS in the bovine pineal gland. Bovine pineals were processed by immunohistochemistry for angiotensinogen, angiotensins I and II, as well as for renin. Frozen pineals were processed by "in situ" hybridization for angiotensinogen and renin mRNAs. Angiotensin converting enzyme(ACE), aminopeptidase A and angiotensin III (AIII) were not investigated. Our data showed that a number of pinealocytes stains for angiotensins (AI and AII), but the renin staining was negative. No nerve fibres were stained with AI or AII. The angiotensins-positive cells were dispersed in the pineal parenchyma, without a particular distribution in relation to the blood vessels. The angiotensinogen immunohistochemistry showed sparse positive cells. The "in situ" hybridization data showed the signal for angiotensinogen mRNA located over pinealocytes, while the renin mRNA was absent. The local synthesis of angiotensinogen in the bovine pineal cells, as a substrate for generation of AI and AII are supported by our data. However, at least the first enzyme involved in this cascade is different from the typical renin. The presence of an angiotensin system without renin in the pineal gland is an additional argument to the evidence that angiotensin II and related peptides can be formed by renin- and ACE- independent protease pathways.

Keywords: pineal cells, renin-angiotensin system, angiotensinogen, in situ hybridization, paracrine regulation

Correspondence: Mihail Gr. Coculescu, Department of Endocrinology, “Carol Davila” University of Medicine and Pharmacy, 34-36 Bd. Aviatorilor, Code 011863, Bucharest, Tel/Fax: + 4021 3198718, e-mail: m.coculescu@uni-davila.ro