Serum Components Stimulate Pericardial Tissue Contraction
Douglas C. Marchion MS, Josh J. Sticka BS, Tian Hao Han, Patricia A. Weber DrPH, David T. Cheung PhD, Albert C. Grobe MS, Carlos M. G. Duran MD

A partial characterization of the component(s) of serum that stimulate pericardial tissue contraction in vitro was carried out. The molecular weight range and stability of the serum component(s) are described. The requirement of protein synthesis during the process of tissue contraction is also reported. Pericardial sections were incubated with fractionated, heat-treated, or protease-treated serum. SDS-PAGE protein profiles were also generated using tissues incubated with cycloheximide for up to 12 days. Tissue contraction was observed in all serum fractions >5 kDa, as well as in samples incubated with heat and protease-treated serum. SDS-PAGE showed the appearance of a protein band after day 4 that was absent in samples incubated with cycloheximide. In conclusion, fractions of serum >5 kDa stimulated protein synthesis and pericardial tissue contraction. The active component(s) was shown to be heat stable but partially sensitive to protease. The addition of cycloheximide to the culture medium inhibited de-novo synthesis of a protein that appeared during the process of tissue contraction.