We have reported that
norepinephrine (NE) and
angiotensin II (Ang II) increase
CaM kinase II activity, which, in turn, activates cytosolic
phospholipase A(2) (PLA(2)) and releases
arachidonic acid. The products of
arachidonic acid generated via
cytochrome P-450 and
lipoxygenase contribute to the development of
hypertension and vascular smooth muscle cell (VSMC)
hyperplasia. The purpose of this study was to investigate whether
CaM kinase II contributes to VSMC proliferation elicited by NE and Ang II and to
hypertension induced by Ang II. NE (1 micromol/L) and Ang II (1 micromol/L) increased proliferation of rabbit aortic VSMC as measured by increased [(3)H]-
thymidine incorporation; this effect of NE and Ang II was attenuated 88 +/- 10% and 64 +/- 11% by the
CaM kinase II inhibitor
KN-93, respectively. Infusion of Ang II with miniosmotic pumps (350 ng/min for 6 days) in rats elevated mean arterial pressure (MABP), which was reduced by simultaneous infusion of
KN-93 (578 ng/min, for 6 days) (Ang II alone: MABP =174 +/- 3 mm Hg, n=12 versus Ang II +
KN-93: MABP 123 +/- 5 mm Hg, n=4, P<0.05). Administration of
KN-93 as a single bolus injection (16 mg/Kg), but not its vehicle, in Ang II--infused hypertensive animals also decreased MABP from 179 +/- 9 mm Hg to 109 +/- 6 mm Hg (n=5, P<0.05).
CaM kinase II activity was increased in the kidney of Ang II--infused hypertensive animals compared with normotensive controls. Treatment with
KN-93 reduced
CaM kinase II activity and ameliorated the intravascular injury in the kidneys of Ang II--infused hypertensive rats. Our data indicate that CaM
kinase activation represents an important component of the mechanism(s) initiating VSMC proliferation and the development and maintenance of Ang II--induced
hypertension in rat.