1. Intracellular calmodulin levels were measured by direct radioimmunoassay in spontaneously hypertensive rats (SHR) and Wistar—Kyoto rats (WKY).
2. Decreased calmodulin levels were demonstrated in the brain, heart, aorta and kidney of spontaneously hypertensive rats compared with those in Wistar—Kyoto rats.
3. Calmodulin levels in the brain were also decreased in deoxycorticosterone acetate (DOCA)-salt rats, but not changed significantly in the heart, aorta and kidney compared with those in Wistar—Kyoto rats.
4. These findings suggest that intracellular calcium-dependent regulatory systems are genetically disrupted in spontaneously hypertensive rats, but this is probably not an important factor in the development of hypertension.