Nuclear pores in ventricular muscle cells from adult hypertrophied hearts

Abstract

Nuclear pores were observed in myocardial cells in both spontaneous and experimentally induced hypertrophy. The ultrastructure of these pores was studied in cross sections and tangential sections of hypertrophied rabbit, hamster and guinea pig heart cells. The morphology was similar to that previously seen in normal cardiac cells and in other cell types. Clusters of nuclear pores were frequently seen, and the closest center-to-center spacing between pores was 1400 Å. Annular granules with associated fibrils were observed on both the cytoplasmic and nucleoplasmic sides of the nuclear envelope. Many of the pores contained granules ∼ 300 Å in diameter which sometimes appeared hollow. The presence of large numbers of nuclear pores in hypertrophied cardiac cells supports the hypothesis that transport of material necessary for RNA-mediated protein synthesis may occur through the pores. Furthermore the mature cardiocyte provides an opportunity to study nuclear pore function in nuclei that do not synthesize DNA or divide.