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Growth factors downregulate vascular smooth muscle thromboxane receptors independent of cell growth

G W Dorn1, M W Becker

  • 1Department of Medicine/Cardiology, University of Cincinnati College of Medicine, Ohio 45267.

The American Journal of Physiology
|April 1, 1992
PubMed

Insights

Growth factors, including serum, downregulate thromboxane A2 (TxA2) receptors in vascular smooth muscle cells. This effect on TxA2 receptors is independent of cell proliferation or DNA synthesis.

Area of Science:

  • Vascular Biology
  • Cell Signaling
  • Smooth Muscle Physiology

Background:

  • Growth factors influence vascular smooth muscle cell (VSMC) differentiation and function.
  • Thromboxane A2 (TxA2) is a potent vasoconstrictor that acts via specific receptors on VSMCs.

Purpose of the Study:

  • To investigate the regulatory effects of serum and defined growth factors on TxA2 receptors in cultured rabbit aorta smooth muscle cells.
  • To determine if growth factor-induced modulation of TxA2 receptors is linked to mitogenic activity.

Main Methods:

  • Cultured rabbit aorta smooth muscle cells were treated with fetal bovine serum (FBS) or specific growth factors.
  • Thromboxane A2 receptor density was measured using radioligand binding assays.
  • TxA2-stimulated phosphatidylinositol hydrolysis was assessed.
  • Cell proliferation and DNA synthesis were monitored.

Main Results:

  • 10% FBS significantly decreased TxA2 receptor density (41%) and attenuated TxA2-stimulated phosphatidylinositol hydrolysis.
  • FBS-induced downregulation of TxA2 receptors was reversible upon serum withdrawal.
  • Heparin inhibited cell proliferation but not serum-induced receptor downregulation.
  • Platelet-derived growth factor and basic fibroblast growth factor reduced TxA2 receptors without affecting cell proliferation or DNA synthesis.

Conclusions:

  • Growth factors, independent of their mitogenic effects, can downregulate TxA2 receptors in vascular smooth muscle cells.
  • This represents a novel regulatory mechanism for vasoconstrictor receptors in the vasculature.
  • These findings have implications for understanding vascular tone regulation and disease pathogenesis.

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