The postnatal decline of hemoglobin F synthesis in normal full-term infants

Area of Science:

• Biochemistry
• Hematology
• Pediatrics

Background:

• Hemoglobin F (Hb F) is the primary oxygen-carrying protein in fetal red blood cells.
• Hemoglobin A (Hb A) gradually replaces Hb F after birth, a process known as the switchover.
• Understanding this transition is crucial for diagnosing and managing certain blood disorders.

Purpose of the Study:

• To quantify the synthesis rates of Hb F and Hb A in normal infants during the first year of life.
• To delineate the complete switchover process from Hb F to Hb A synthesis in relation to postnatal and postconceptional age.

Main Methods:

• Blood samples from 37 infants were analyzed using [14C]leucine incorporation to measure protein synthesis.
• Hemoglobin fractions (Hb F and Hb A) were separated using DEAE-Sephadex chromatography.
• Globin chain chromatography on carboxylmethyl cellulose confirmed the purity of separated hemoglobin fractions.

Main Results:

• Hb F synthesis demonstrated a rapid postnatal decline, reaching 3.2% ± 2.1% by 16-20 weeks of age.
• Combining current data with previous studies, the Hb F to Hb A switchover follows a sigmoid curve.
• The steepest part of the curve occurs between 30 and 52 postconceptional weeks, with preceding and succeeding plateaus of Hb F synthesis.

Conclusions:

• The switchover from fetal hemoglobin (Hb F) to adult hemoglobin (Hb A) synthesis is a well-defined process in human infants.
• Postconceptional age is a key factor in describing the timing and completion of this hemoglobin transition.
• This research provides a quantitative framework for the normal hemoglobin switchover, aiding in the understanding of related physiological and pathological conditions.