We have tested the hypothesis that growth factor signaling pathways are augmented in hypertension, a disease associated with vascular smooth muscle cell growth. Thoracic aorta was dissected from deoxycorticosterone acetate-salt (DOCA-salt) and one kidney, one clip (1K, 1C) hypertensive rats and from sham normotensive rats for use in isolated tissue bath experiments. Systolic blood pressure was significantly higher in DOCA-salt and 1K, 1C than in normotensive sham rats: 192 ± 7, 185 ± 10, and 117 ± 4 mmHg, respectively. Although virtually no contraction to epidermal growth factor (EGF) was observed in endothelium-denuded sham rat aorta [1 ± 1% phenylephrine (PE) (10 µmol/l)-induced contraction], the maximal EGF-induced contraction was 45 ± 7% in endothelium-denuded aorta from DOCA-salt hypertensive rats and 39 ± 7% in aorta from 1K, 1C rats. Although slightly attenuated, a contraction to EGF was still observed in endothelium-intact aortic strips from 28-day DOCA-salt hypertensive rats. We also conducted concentration-response curves to EGF on days 1, 3, 5, 7, 14, and 21 of DOCA-salt therapy. A significant contraction to EGF in aorta from DOCA-salt rats was observed on day 14, when DOCA-salt rats had significantly higher blood pressure than sham rats: 188 ± 6 and 122 ± 3 mmHg, respectively. Transforming growth factor-, an agonist of the EGF receptor, contracted DOCA-salt rat aorta (30 ± 7% PE-induced contraction) but not sham aorta (3 ± 3%). The EGF receptor tyrosine kinase inhibitor 4,5-dianilinophthalimide (10 µmol/l), the mitogen-activated protein kinase kinase inhibitor PD-098059 (10 µmol/l), and the L-type voltage-gated calcium channel inhibitor diltiazem (1 mol/l), but not the cyclooxygenase inhibitor indomethacin (10 µmol/l), virtually abolished EGF-induced contraction (85, 98, and 99% reduction, respectively). These data support a striking difference in EGF signaling between normotensive and hypertensive animals. Furthermore, they provide evidence that growth factors should be considered vasoconstrictors as well as growth modulators in hypertension.

deoxycorticosterone acetate-salt hypertension; vascular smooth muscle; tyrosine kinases; contraction; mitogen-activated protein kinase kinase

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