Effects of hypertension and aging on platelet-derived growth factor and platelet-derived growth factor receptor expression in rat aorta and heart

Abstract

Previous investigations have demonstrated certain similarities in the cellular changes occurring in the arterial wall in response to hypertension and aging. We undertook the current studies to examine the expression of platelet-derived growth factor (PDGF) receptors and ligands and transforming growth factor-beta 1 (TGF-beta 1) in aorta and heart of spontaneously hypertensive rats (SHRs), Wistar-Kyoto (WKY) controls, and Wistar rats studied at ages ranging from 5 to 40 weeks. A progressive increase with age in aortic steady-state messenger RNA (mRNA) levels of the receptor for the B chain of PDGF (PDGF-r beta) was present in all three strains but was greatest in the SHR. The aortic expression of PDGF A or B ligands as well as of the PDGF-r alpha-receptor was not significantly influenced by age or blood pressure. In contrast, in the heart of the SHR and WKY rat, there was an age-related decrease in expression of both PDGF receptors and of the PDGF B chain. Hypertension and aging were associated with increases in steady-state mRNA for TGF-beta 1 in aorta, but in the heart, reductions again were observed. These studies indicate that both hypertension and aging increase the in vivo expression of PDGF-r beta and TGF-beta 1 in aortic tissue. Such changes might be functionally significant and provide autocrine or paracrine mechanisms for regulation of cellular growth in the arterial wall in response to these conditions. The findings also provide further support for the concept that hypertension accelerates the arterial changes associated with aging.