Aortic smooth muscle cell phenotypic modulation and fibrillar collagen deposition in angiotensin II-dependent hypertension.
BACKGROUND
We investigated the effect of nifedipine, AT-1 and ET-1 receptor blockade on arterial smooth muscle cell phenotypes and collagen deposition in TGRen2 transgenic rat (TGR).


METHODS
Four-week-old TGR were blood pressure (BP)-matched and allocated to receive a placebo (n=8), the calcium antagonist nifedipine (n=6), the AT-1 specific receptor antagonist irbesartan (n=6), the ET(A)/ET(B) antagonist bosentan (n=6) or the ET(A)-selective antagonist BMS-182874 (n=5). Sprague-Dawley normotensive rats served as controls (n=6). After 4 weeks of treatment animals were euthanized and the left ventricle (LV) and the structural changes in intracardiac arterioles and aorta were assessed histomorphometrically. Smooth muscle cell phenotypes and fibrillar collagen content of the aortic wall were evaluated by immunostaining, using differentiation markers-specific antibodies and Syrius red staining, respectively. The changes in ET(A) and ET(B) receptor density were also assessed with quantitative autoradiography.


RESULTS
Compared to placebo, only irbesartan lowered BP (P<0.001) and prevented LV and small resistance artery hypertrophy. The aorta of placebo-treated TGR showed an increase in foetal-type smooth muscle cell content and fibrillar collagen staining, compared to controls. These changes were blunted by irbesartan, which increased ET(A) receptors in the arterial wall, enhanced by BMS-182874 and unaffected by bosentan. Nifedipine also blunted both the VSMC and collagen changes despite having no effect on BP and ET(A) receptors.


CONCLUSIONS
In TGRen2, vascular hypertrophy entails both smooth muscle cell phenotypic modulation and collagen deposition. These alterations do not follow closely the BP changes and seem to imply the dihydropyridine-sensitive calcium channels.
Rossi
Gian Paolo
GP
Department of Clinical and Experimental Medicine, Clinica Medica 4, University of Padua, via Giustiniani 2, Italy. gianpaolo.rossi@unipd.it
Cavallin
Martina
M
Belloni
Anna S
AS
Mazzocchi
Giuseppina
G
Nussdorfer
Gastone G
GG
Pessina
Achille C
AC
Sartore
Saverio
S
D000704:Analysis of Variance; D000804:Angiotensin II; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D030801:Animals, Genetically Modified; D000959:Antihypertensive Agents / Q000494:pharmacology; D001011:Aorta; D001713:Biphenyl Compounds / Q000494:pharmacology; D000077300:Bosentan; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003094:Collagen / Q000378:metabolism*; D003619:Dansyl Compounds / Q000494:pharmacology; D004195:Disease Models, Animal; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D006973:Hypertension / Q000378:metabolism* / Q000473:pathology*; D007150:Immunohistochemistry; D000077405:Irbesartan; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000473:pathology*; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology; D013777:Tetrazoles / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D000959:Antihypertensive Agents; D001713:Biphenyl Compounds; D002121:Calcium Channel Blockers; D003619:Dansyl Compounds; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D013449:Sulfonamides; D013777:Tetrazoles; D000804:Angiotensin II; C085754:5-(dimethylamino)-N-(3,4-dimethyl-5-isoxazolyl)-1-naphthalenesulfonamide; D003094:Collagen; D009543:Nifedipine; D000077405:Irbesartan; D000077300:Bosentan