STRESS, ADAPTATION, AND NITRIC-OXIDE

The biological role of nitric oxide (NO) has been studied for more tha n ten years. Nevertheless, the number of investigations in this field continues to increase. It is now suggested that NO is a previously unr ecognized, very important regulator of physiological functions and cel l metabolism in the body. Through the application of the methods of mo lecular biology, more and more data are being accumulated on the regul atory role of NO in the mechanism of gene expression and protein biosy nthesis. The data presented in this review show an important role of N O in stress and adaptive responses of organisms and thereby expand exi sting notions on the biological role of this unique molecule. This rev iew substantiates the idea that the system of NO generation is a newly discovered stress-limiting system. The action of this NO-ergic system is based on the capability of NO to limit key links of the stress rea ction and to enhance the potency of endogenous defense systems of the organism. The role of NO is considered at the major stages of adaptati on: 1) at the urgent stage related with the stress reaction; 2) at the stage of the transition from urgent to longterm adaptation; and 3) at the stage of long-term adaptation characterized by the formation of s table protective effects. It is demonstrated that pharmacological ''im itation'' of the activated NO-ergic system by administration of NO don ors to the organism provides in many instances an efficient protection against stress damage and enhances the adaptive capacity of the organ ism.