Age-related attenuation in the elements in monkey sino-atrial node

Changes in trace elements of the sino-atrial (SA) node with aging was investigated using 24 hearts of the Japanese and rhesus monkeys of ages ranging from 27 d to 30 yr. With aging, sympathetic activity decreases and SA nodal function deterionates. The SA nodal tissue was removed from the anatomical position and was confirmed by means of histological observation. The elements, such as Ca, P, S, Mg, Na, Fe, and Zn, were analyzed using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Advancing age never increased the contents of the trace elements, but decreased them. The correlation coefficients for the age-dependent attenuations were −0.561 (n=24, p<0.01) in Ca and −0.482 (n=24, p<0.05) in P. The correlations for the attenuations induced by other trace elements were not significant. Furthermore, close relationships of the elements between Ca and P, S, Zn, or Na contents, between P and Zn or Na contents, and between Zn and Na contents were observed. These results indicate that the elements in the monkey SA node are attenuated with an increase in age, presumably suggesting the age-related suppression of cardiac functions as a result of the histological alterations of the SA nodal cells.