ENHANCED PHOSPHOLIPASE-D ACTIVITY IN VASCULAR SMOOTH-MUSCLE CELLS DERIVED FROM SPONTANEOUSLY HYPERTENSIVE RATS

When cultured in the presence of fetal calf serum, aortic vascular smo oth muscle cells (VSMC) derived from spontaneously hypertensive rats ( SHR) grow faster than those from normotensive control Wistar-Kyoto (WK Y) rats. In order to investigate the mechanism underlying this growth abnormality, we measured phospholipase D (PLD) activity in VSMC taken from both SHR and WKY rats. Upon stimulation with serum, platelet-deri ved growth factor (PDGF) and porbol 12-myristate 13-acetate (TPA), pho sphatidylethanol (PEt) was produced in the presence of ethanol. The re sponses of the VSMC from SHR (SHR-cells) to all stimuli were significa ntly greater than those of the VSMC from WKY rats (WKY-cells), which s uggests an enhanced PLD activity in the SHR-cells. Since PLD is regard ed as an enzyme involved in signal transduction leading to cell prolif eration, this PLD hyper-reactivity in the SHR-cells may account at lea st partially for the growth abnormality in the SHR-cells.