Abstract: Disclosed are pharmaceutical composition of a sterile, injectable physiologically acceptable solution containing nitric oxide (NO), processes for preparing the compositions and a process for detecting physiologically present NO. With these NO solutions, NO in high doses can trigger locally in vessels, e.g. coronary vessels, specific local biological effects such as relaxation of the smooth vascular musculature, inhibition of thee adhesion of thrombocytes, etc., without producing systemic side-effects, such as for example, a critical drop in blood pressure, in spite of the high does. The detection process enables the presence of an endothelial dysfunction to be established from the whole blood of humans and other mammals.