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BACKGROUND. To date, the mechanisms of small stone elimination by lithokinetic therapy (LCT) have not been elucidated.   THE AIM of this investigation was to estimate the activity of receptors controlling the contraction and relaxation of smooth muscle cells (SMC) against the background of α1A-adrenoreceptor blockade during LCT in patients with small stones localization in the middle third of ureter.   PATIENTS AND METHODS. The study was prospective and included 40 patients in whom standard LCT was done for localization of small concrements (≤6 mm) in the middle third of ureter. The functional activity of receptors modulating ureteric peristalsis was analyzed in vitro using platelet suspension. The agonists used were ATP, ADP, adenosine, epinephrine, angiotensin-2 (Sigma-Aldrich Chemie GmbH, Germany) at EC50 concentrations causing aggregation at 50 % in healthy subjects. Platelet aggregation was assessed by turbidimetric method on ChronoLog analyzer (USA).   RESULTS. No differences in the rate of small concrements elimination from the middle third of ureter was found in presence and absence of α1A-adrenoreceptor blocker in LCT. Before LCT, α2-adrenoreceptor hyperresponsiveness, normoreponsiveness of purine P2X1- and P2Y-receptors, adenosine A2-receptor and angiotensin AT1-receptor were found. After 9 days of LCT with verified elimination of concrements, an increase in P2X1-receptor and AT1-receptor activity (p < 0.001) was found regardless of the administration of α1A-adrenoceptor blocker. P2Y-receptor hyperresponsiveness was seen in the presence and normoreponsiveness in the absence of α1A-adrenoreceptor blocker in LCT.   CONCLUSION. At the lithokinetic therapy irrespective of α1A-adrenoreceptor blocker prescription, compensatory mechanisms, aimed at enhancement of contractile activity and preservation of smooth muscle cell relaxation take part in the traffics of small concrements from the middle third of ureter.

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