ИСТИНА

Basilar artery (BA, cerebral) and saphenous artery (SA, hindlimb cutaneous) of C57BL/6 mice demonstrated qualitatively different alterations after 30-day-long spaceflight on the Bion-M №1 biosatellite, so that the endothelium-dependent relaxation (EDR) to acetylcholine was suppressed in BA but moderately augmented in SA. In this study, we tested the hypothesis that, apart from the location in the mouse body, such diverse post-flight alterations are associated with the differences in EDR mechanisms in these arteries. We mounted arterial segments in wire myograph (DMT) and studied the components of EDR by pharmacological inhibition. Indomethacin, L-NNA and the combination of IKCa/SKCa blockers (TRAM-34+UCL-1684) were used as inhibitors for cyclooxygenase and NO-synthase and endothelium-derived hyperpolarizing factor (EDHF), respectively. Application of all blockers together eliminated EDR response in both arteries. Indomethacin alone did not affect EDR of either artery indicating a negligible contribution of prostanoids to the response. L-NNA halved EDR in BA as well as SA, pointing to the prominent and comparable NO-components in two arteries. Along with that, removal of the EDHF effects provided much smaller inhibition of EDR in SA compared to BA. However, EHDF-component in SA was high when studied after combined NO-synthase and cyclooxygenase blockade, indicating a paradoxical redistribution of EDR components in this artery. We suggest, that such redistribution of EDR components may be important for adaptation of vascular endothelium to spaceflight conditions. Cerebral artery lack the possibility of EDR mechanisms redistribution and its EDR response is reduced. Hindlimb cutaneous artery on the contrary shows vigorous redistribution of EDR mechanisms, that can underlie the unchanged or even elevated EDR response after spaceflight in this vascular bed.