[56] Regulation of parvalbumin concentration in mammalian muscle

Parvalbumin (PA), an acidic Ca2+- and Mg2+-binding protein of approximately 12,000 Mr, is thought to act in skeletal muscle as a cytosolic Ca2+- and Mg2+-buffering compound. In mammalian muscle, it has been detected exclusively in fast-twitch fibers. Several studies have shown that the PA concentration in skeletal muscle is subject to regulation by exogenous factors and may be altered experimentally by changes in contractile and/or motoneuron activity. It has also been shown that PA is reduced in hereditary mammalian muscle diseases. The influence of neural activity upon PA expression is clearly shown by denervation, cross-reinnervation, and nerve-stimulation experiments. Denervation of neonatal and adult fast-twitch muscles suppresses PA synthesis. Its concentration remains low in denervated, presumptive fast-twitch muscles of the newborn rabbit. PA synthesis is suppressed in fast-twitch muscle after cross-reinnervation with a nerve that normally supplies a slow-twitch muscle. In view of the different activity patterns of fast and slow motoneurons, it seems likely that PA expression is under the positive control of phasic, high-frequency activity as delivered by fast motoneurons.