FEATURES OF L-ARGININE-CITRULLINE CYCLE FUNCTIONING IN PATIENTS WITH MULTIPLE MYELOMA WITH CONCOMITANT CORONARY HEART DISEASE.

Background: Disorders of the L-arginine-citrulline cycle affect the functioning of the cardiovascular system. Cancerinduced augmentation of arginase activity stimulates the biotransformation of L-arginine to form polyamines, which causes NO deficiency and increases the risk of endothelial dysfunction in the category of high-risk patients for developing cytostatic-induced cardiotoxicity. The aim was to investigate features of L-arginine-citrulline cycle functioning in patients with multiple myeloma (MM) and concomitant coronary artery disease (CAD) during chemotherapy (CT).

Materials and methods: 42 patients with MM progression were examined and divided into 2 groups: group І (n = 20) - patients without CAD and group II (n = 22) - patients with CAD. The concentrations of L-arginine and citrulline and the activity of arginase in the blood serum of the patients were measured before and after the 1st and 5th courses of chemotherapy.

Results: Before chemotherapy, in patients of both groups, the blood serum level of L-arginine decreased, while the activity of arginase and the level of citrulline increased compared to healthy individuals. In patients of group II, the level of citrulline was higher than in patients of group I. After the 5th course of chemotherapy, L-arginine content in patients of both groups increased and citrulline levels decreased compared to the initial examination.

Conclusions: The progression of MM was accompanied by a decrease in the blood serum content of L-arginine along with an increase in the arginase activity in the blood serum compared to practically healthy individuals. An increase in the cumulative dose of cytostatics during CT in the MM patients with concomitant CAD led to a decrease in the content of L-arginine in the blood serum with a simultaneous increase in the content of citrulline compared to corresponding levels in MM patients without concomitant CAD.