Studies on Human Myoglobin II. Fetal Myoglobin: Its Identification and Its Replacement by Adult Myoglobin During Infancy

By KARL SINGER, BASIL ANGELOPOULOS AND BRACHA RAMOT I T IS N(.)W well established that the erythrocytes of normal newborns contain about 50 to 90 per cent of fetal (type F) hemoglobin, the remainder being supplied by the normal adult (type A) pigment. As a rule, the fetal hemoglobin is rapidly replaced by the adult compound and after 7 to 12 months the embryonic pigment is no longer demonstrable with the alkali denaturation techmiic.’ However, in some normal infants, small amounts (3 to 5 per cent) of fetal hemoglobin may persist for a period of several years.2 ‘ Furthermore, it is now known that the production of F hemoglobin never ceases in some hereditary hemolytic disorders,4 and that it may be resumed in some acquired hematologic conditions.5 Several investigators have also searched for a fetal type of myoglobin.69 Although some data are available suggesting the existence of such a type of muscle pigment, a sharp characterization of this protein has not been accompushed. Iii this commumcation, experiments are reported which show that fetal human myoglohimi (Mb F) differs distinctly from adult myoglobin (Mb A) whets exammed by spectroscopic and electrophoretic technics. Mb F was identified as the sole type of myoglobin present in premature infants and in normal newborns. Replacement of Mb F by Mb A takes place during the first six months of life.