IMMUNOHISTOCHEMISTRY: MYOGLOBIN

MYOGLOBIN (MB) IS AN IRON & OXYGEN BINDING PROTEIN FOUND IN THE SKELETAL MUSCLE TISSUE OF VERTEBRATES IN GENERAL AND IN ALMOST ALL MAMMALS. COMPARED TO HEMOGLOBIN, MYOGLOBIN HAS A HIGHER AFFINITY FOR OXYGEN. MYOGLOBIN IS ONLY FOUND IN THE BLOODSTREAM AFTER MUSCLE INJURY. MYOGLOBIN IS FOUND IN TYPE I, TYPE II A, AND TYPE II B SKELETAL MUSCLES. ALTHOUGH ITS HEME GROUP IS IDENTICAL TO THAT IN HB, MB HAS A HIGHER AFFINITY FOR OXYGEN THAN HEMOGLOBIN. MYOGLOBIN IS RELEASED FROM DAMAGED MUSCLE TISSUE (RHABDOMYOLYSIS). THE RELEASED MYOGLOBIN IS FILTERED BY THE KIDNEYS BUT IS TOXIC TO THE RENAL TUBULAR EPITHELIUM AND MAY CAUSE ACUTE KIDNEY INJURY, CHARACTERIZED BY PRESENCE OF COARSE GRANULAR/ STRINGY CASTS IN TUBULAR LUMINA, WHICH STAIN POSITIVELY FOR ANTIBODIES AGAINST MYOGLOBIN M(MYOGLOBIN CAST NEPHROPATHY). THE FERRIHEMATE PORTION THAT IS DISSOCIATED FROM MYOGLOBIN IN ACIDIC ENVIRONMENTS (E.G., ACIDIC URINE, LYSOSOMES) IS RESPONSIBLE FOR RENAL TOXICITY.