The level of cGMP in myocytes of uterus of rats at an action active metabolities of nitrogen and oxygen (NO, NO2- and H2O2) in the conditions of influence of progesteron on myocytes was studied. Cell suspension was selected with the use of collagenase and soy-bean inhibitor of tripsin. Determining the amount of cGMP was conducted with the use of standard kit produced by "Amersham" (Great Britain). The basal level of cGMP in unactivated myocytes made 1.5 +/- 0.17 pmol cGMP/mg of protein (n = 5). It is shown that incubation of myocytes with 0.1 mM acetylcholin during 1 hour resulted in 2 times growth of cGMP content in suspension approximately, this increase is fully supressed in the presenced 0.1 mM methilene blue, that specifies activity of soluble cGMP in myocytes. Treatment of cells with 10 nM progesteron during 1 hour did not cause substantial changes in the level of cGMP. At the same time addition of 0.1 mM sodium nitroprussid or 10 nM H2O2 to suspension resulted in such conditions in the increase of level of cGMP to 3.1 +/- 0.6 and 6.8 +/- 0.4 pmol cGMP/mg of protein. Poor penetration of NO2- (10 nM) to the cells did not cause changes in the level of cGMP. The results got by us testify that the long-term influence of active metabolities of nitrogen and oxygen, instead of progesteron, provides the increase of the level of cGMP in the myometrium.