A new method for the histological study of aging changes in the sinoatrial node.

In the autopsied heart, histological observation of specialized conducting cells, especially in the sinoatrial node, is very difficult. Conducting cells were investigated and classified in electron microscopic studies which were not adapted to the examination of the autopsied heart. In this study, we aimed to obtain a clear understanding of the microenvironment in the sinoatrial node of autopsied hearts. For this purpose, we prepared 1 mu thick sections using epon embedding methods for electron microscopy. Thus, we were able to isolate human SA nodal cells from the background collagen fiber, and morphological classification of conducting cells was enhanced. We examined histologically SA nodal cells from various age groups (20-86 years of age), and calculated the mean diameter and number of nodal cells in 4 age groups. SA nodal cells increased in diameter and decreased in number with aging.