Hypertension-induced changes of platelet-derived growth factor receptor expression in rat aorta and heart

Hypertension-associated growth of vascular smooth muscle cells might be mediated in vivo by platelet-derived growth factor (PDGF). Our previous investigations in hypertensive rats failed to demonstrate changes in aortic steady-state mRNA levels of PDGF A or B chains. The current studies were performed to determine whether hypertension might affect the expression of PDGF receptors. We studied PDGF α- and β-receptor gene expression by Northern analysis using human and rat cDNA probes. Studies of tissue distribution revealed that PDGF α-receptor mRNA was most abundant in total aorta and aortic media, whereas the PDGF α-receptor mRNA was most abundant in the lung and was expressed at low levels in aortic tissue. Deoxycorticosterone acetate (DOCA)-salt hypertension induced a threefold increase in aortic steady-state PDGF β-receptor mRNA levels. Aortic PDGF β-receptor expression also was higher in spontaneously hypertensive rats (SHRs) when compared with age-matched normotensive Wistar-Kyoto (WKY) controls. Aortic PDGF α-receptor steady-state mRNA levels were unchanged in DOCA-salt hypertension and were expressed at similar levels in WKY rats and SHRs. Unlike the findings with aorta, cardiac PDGF β- and α-receptor and PDGF B-chain expressions were unchanged in the DOCA-salt model and were decreased in SHRs. These findings indicate that hypertension can increase aortic steady-state mRNA levels for PDGF β-receptor. They also indicate that tissue-specific expression of the genes of the PDGF ligand/receptor system are differentially regulated in hypertension.