TGFB1 and pulmonary hypertension, primary, 1: The mRNA expression of TGF-β1 and the protein level of active TGF-β1 homodimers (25kda) in the livers of PHT rats were significantly increased, while the protein levels of inactive TGF-β1 monodimers (12kda) and precursor (44kda) were significantly decreased (Figures 3B, C).