Renovascular hypertension is characterized by
stenosis of the renal artery and high plasma
renin levels. The renal phenotype is characterized by high levels of
renin in the hypoperfused kidney due to the recruitment of
renin-producing cells along the afferent arterioles. This increase in myoepithelioïd cells is due mainly to the differentiation of existing smooth muscle cells with acquisition of a secretory phenotype. To understand the molecular mechanisms involved in this recruitment, we used the established rat model of
renovascular hypertension known as the two-kidney, one-
clip model in the Lewis rat. Renal arterioles were isolated using magnetized
iron suspension. Differential proteomic analysis was performed using 2-D
polyacrylamide gel electrophoresis followed by mass spectrometry. Comparative analysis of soluble
proteins extracted from afferent arterioles of clipped and contralateral kidneys showed 14
proteins significantly differentially expressed by at least
a factor of 2. These
proteins were identified by mass spectrometry. The most striking
protein revealed by proteomics is
troponin T, which is down-regulated in the afferent arterioles of the clipped kidney. Confocal microscopy showed that
troponin T is specific of the smooth muscle phenotype and absent in the myoepithelioïd phenotype. Our data suggest that
troponin T is only present in renal smooth muscle cells.