Paying the piper: the cost of Ca2+ pumping during the mating call of toadfish

摘要

Non-technical summaryThe fastest contracting vertebrate muscle known is found in toadfish. This muscle surrounds the gas-filled swimbladder of males and contracts and relaxes at 100–200 times per second, producing a mating call. Because calcium ions, the trigger for muscle contraction, must be released and taken up (‘pumped’) on each contraction, this muscle would seem to require a prodigious rate of Ca²⁺ pumping. Previous work, however, indicates that (1) the pumping proteins in toadfish are not particularly fast, and (2) the mating calls are short (400 ms), interleaved with long (5–15 s) intercall intervals. The present study shows that the Ca²⁺ pumping paradox is solved in two ways: (1) the amount of Ca²⁺ released per stimulus is reduced (which also avoids running out of Ca²⁺), and (2) the muscle's high concentration of the protein parvalbumin binds released Ca²⁺ during a call, thereby allowing most pumping to occur during the intercall interval.