Angiotensin receptors in the eyes of arterial hypertensive rats.
OBJECTIVE
The aim of the present study was to determine whether the eye tissues of arterial hypertensive rats evince expression of angiotensin receptors (AT(1) and AT(2)) as well as the novel Mas receptor, whose endogenous ligand is vasorelaxing Angiotensin (1-7) [Ang (1-7)].


METHODS
Enucleated eyes from spontaneously hypertensive rats (SHR) and double transgenic rats harbouring human renin and angiotensinogen genes (dTGR) and their normotensive controls were used. Half of the rats were pretreated orally with an Angiotensin II (Ang II) type 1 receptor blocker (ARB). The eyes were snap-frozen in isopentane at -40 degrees and stored at -70 degrees for subsequent reverse transcriptase polymerase chain reaction (RT-PCR) analysis or in vitro autoradiography.


RESULTS
The mRNA expression of AT(1a) and AT(2) as well as the novel Mas receptor was detected in all rat groups, being markedly higher in the retina than in the ciliary body. dTGR had significantly more receptors than SHR, but no direct relation to blood pressure level was seen. According to the autoradiography, treatment with ARB blocked a part of AT(1) receptors but had no clear effect on AT(2) receptors.


CONCLUSIONS
The novel Mas receptor was found by RT-PCR in eye tissue for the first time. Its specific ligand, Ang (1-7), may be involved in the regulation of intraocular pressure--as recently demonstrated by us--and in the pathogenesis of retinal diseases as a counter-regulatory component for the vascular and proliferative actions of Ang II. The results suggest that the density of AT(1) receptors in the eye is independent of the blood pressure level of the animal.
Vaajanen
Anu
A
Department of Pharmacology, Institute of Biomedicine, University of Helsinki, Finland.
Lakkisto
Päivi
P
Virtanen
Ismo
I
Kankuri
Esko
E
Oksala
Olli
O
Vapaatalo
Heikki
H
Tikkanen
Ilkka
I
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000808:Angiotensinogen / Q000235:genetics; D000818:Animals; D030801:Animals, Genetically Modified; D001345:Autoradiography; D001794:Blood Pressure; D002924:Ciliary Body / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006973:Hypertension / Q000235:genetics*; D007429:Intraocular Pressure; D008297:Male; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics*; D044139:Receptor, Angiotensin, Type 2 / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics; D012083:Renin / Q000235:genetics; D012160:Retina / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D047228:Angiotensin II Type 1 Receptor Blockers; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D043562:Receptors, G-Protein-Coupled; D000808:Angiotensinogen; D012083:Renin