ciclosporin also binds to the cyclophilin d protein that constitutes part of the mitochondrial permeability transition pore (mptp). the mptp is found in the mitochondrial membrane of cardiac muscle cells and moves calcium ions () into the mitochondria. when open, enters the mitochondria and causes the muscle cells (and thus the heart) to contract. if unregulated, the influx of can contribute to mitochondrial swelling and dysfunction.