Expression of peroxisome proliferator-activated receptors γ changes with age in vascular smooth muscle cells of spontaneously hypertensive rat

Objective: In order to elucidate the relationship between PPAR-γ and the development of hypertension, we detected the expression of peroxisome proliferator-activated receptors γ(PPAR-γ) in the vascular smooth muscle cells (VSMCs)and the VSMC proliferation of spontaneously hypertensive rats (SHR) at different ages. Methods: The expression of PPAR-γ in the intact vascular tissues of rats at different ages were detected by immunohistochemistry. Aortic VSMCs were cultured. PPAR-γ mRNA in primary and low-passage cultured VSMCs of various ages were determined by RT-PCR, and proteins were evaluated by immunohistochemistry and age matched Western Blot. Age matched Wistar-Kyoto rats (WKY) were used as control. Results: This experiment demonstrated that the expression of PPAR-γ increased with age in the intact aorta tissues of SHR. The expression of PPAR-γ did not continuously increase in 24w-old SHR when compared with that in 16w-old SHR. No difference between 4w-, 24w-old SHR and age matched WKY was observed, but the expression of PPAR-γ was greater in 8w- and 16w old SHR than in age matched WKY. In primary and low-passage cultured VSMCs, the expression of PPAR-γ mRNA and protein increased with age both in SHR VSMCs and WKY VSMCs of 4w, 8w and 16w old, and no difference between 4w- and 24w-old SHR and WKY was noted, but the expression of PPAR-γ was higher in 8w- and 16w-old SHR than in age matched WKY. PPAR-γ expression in 24w-old SHR did not increase and it was equal to 16w-old SHR and 24w-old WKY. Conclusion: These datas on SHR suggest that the expression of PPAR-γ changes with age and the development of high blood pressure. PPAR-γ expression may play a compensatory role in hypertension, but this compensatory action is limited.