Constitutive TPO gene expression in the human fetus. No correlations were found between the total TPO mRNA amount expressed in liver, kidney, and spleen (in fmol per individual) and (A) blood platelet count (in cells per microliter); (B) serum TPO concentration (in pg/mL); (C) gestational age (in weeks). Total TPO mRNA was calculated from the TPO mRNA concentration per gram tissue and the organ weight as the sum of the TPO mRNA amount of liver, kidneys, and spleen. TPO mRNA produced in lung and bone marrow was not included because the organ weights could not be determined.