Resting Load and Modulation of the Myofilament Ca2+Sensitivity in Rabbit Cerebral Arteries

Abstract

The effect of preload on myofilament Ca2+sensitivity was examined using α-toxin permeabilization and fura-2 fluorometry in rabbit cerebral arteries. The [Ca2+]i-force curves shifted leftward at a high preload, with a decrease in median effective concentration of Ca2+in the permeabilized artery. In the fura-2-loaded artery, the preload modulated the force without affecting [Ca2+]i levels during K+depolarization, and a high preload moved the [Ca2+]i-force curve upward and to the left. It is thus concluded that the preload regulates the Ca2+sensitivity of the myofilament and, therefore, may play a role in the regulation of cerebral arterial tonus and blood flow.