AGING IS ASSOCIATED WITH REDUCED BASAL AND STIMULATED RELEASE OF NITRIC-OXIDE BY THE CORONARY ENDOTHELIUM

The ageing process is known to be associated with biochemical and func tional changes in the heart. In an attempt to determine whether the ab ility of the coronary endothelium to secrete nitric oxide (NO) both at rest and in response to pharmacological stimulation is age dependent, we studied lour groups of rats of different ages (1.5. 15 and 26 mont hs, respectively). Basal release of NO by endothelium as assessed by r esponse of coronary flow to L-monomethylarginine, an inhibitor of NO s ynthase. was higher in the younger age groups. Similarly. the response of coronary flow to 5-hydroxytryptamine, a selective probe of endothe lial capacity to secrete NO. was diminished in the older animals. This was confirmed by direct measurement of NO by chemiluminescence in the coronary effluent. In contrast, the response to glyceryl trinitrate a ppeared to be unaltered by age. It is concluded that in rats, basal an d stimulated release of nitric oxide by the coronary endothelium deter iorates with age.