Reduction of blood pressure and vascular collagen in the spontaneously hypertensive rat by elastase.

The effects of elastase on collagen biosynthesis and deposition in the aorta, heart and liver were investigated in spontaneously hypertensive rats (SHR). Prolyl hydroxylase activity (EC 1.14. 11.2; proline, 2-oxoglutarate dioxygenase) was significantly increased in the aorta of SHR compared with that of control. When elastase (10 mg/kg, i.p.) was given daily to the SHR for 9-weeks, the blood pressure was 175 +/- 6.0 mm Hg (n = 6), whereas the blood pressure of the untreated SHR was increased to 209 +/- 6.4 mm Hg (n = 6). In contrast, elastase did not influence changes in the blood pressure of normotensive rats (WKY). Prolyl hydroxylase activity and hydroxyproline content in the aorta were significantly smaller than those in non-treated SHR. Urinary excretion of hydroxyproline in SHR was increased by treatment with elastase. However, markers of collagen biosynthesis and deposition in the heart and liver in either SHR or WKY were not modified by treatment with elastase. These results suggest that the lowering of blood pressure in SHR treated with elastase may be related to the decrease of vascular collagen biosynthesis and deposition.