Sex differences in mitochondrial Ca handling in mouse fast-twitch skeletal muscle in vivo.

We investigated sex differences in mitochondrial Ca handling properties in mouse fast-twitch skeletal muscle. Changes in cytoplasmic Ca concentration ([Ca]) were measured in vivo using tibialis anterior muscles from male and female mice. The muscles were exposed to increasing concentrations of cyclopiazonic acid [CPA; sarcoplasmic reticulum (SR) Ca-ATPase inhibitor] (from 10 to 30 to 50 μM at 10 min intervals).

Improved skeletal muscle Ca regulation in vivo following contractions in mice overexpressing PGC-1α.

In skeletal muscle, resting intracellular Ca concentration ([Ca]) homeostasis is exquisitely regulated by Ca transport across the sarcolemmal, mitochondrial, and sarcoplasmic reticulum (SR) membranes. Of these three systems, the relative importance of the mitochondria in [Ca] regulation remains poorly understood in in vivo skeletal muscle. We tested the hypothesis that the capacity for Ca uptake by mitochondria is a primary factor in determining [Ca] regulation in muscle at rest and following contractions.