Chloroquine-induced alterations in phasic muscles: II. Sarcoplasmic reticulum

Chloroquine administration (2.5 mg/100 g for 1 to 7 days) caused swelling of specific regions of the sarcoplasmic reticulum in the phasic posterior latissimus dorsi (PLD) muscle of the chicken. These included the portion of the sarcoplasmic reticulum adjacent to the A and I bands and the region of the sarcoplasmic reticulum (adjacent to the I band) that was acid phosphatase positive in control chicken muscles. The lateral cisternae of sarcoplasmic reticulum and T tubules were unaltered from controls. This swelling may be due to either chloroquine accumulation in the acid phosphatase-positive sarcoplasmic reticulum or a reduced calcium content of the sarcoplasmic reticulum resulting from an inhibition of calcium transport by chloroquine.