Influence of excessive salt consumption on the functional state of microvascular vessels of the skin of rats with renal dysfunction

Abstract

Background. Cardiovascular complications are common in chronic kidney disease (CKD). The relationship between the cardiovascular system and the kidneys is complex and diverse, but the question of the mechanisms of the influence of excess NaCl consumption on the functional state of blood vessels during renal dysfunction remains relevant.The aim: to evaluate the effect of a high-salt diet on the functional state of microcirculatory vessels (MCR) of the skin in rats at an early stage of renal dysfunction.Material and Methods. The study was conducted on Wistar rats. The first SO group included animals subjected to sham surgery (SO) and receiving a standard diet (0.34% NaCl); in the second, HS group – animals that also underwent a sham operation, but received a high-salt diet (4% NaCl); in the third, NE group – rats subjected to ¾ nephrectomy (NE) and receiving a standard diet; the fourth, HS+ NE group included rats subjected to ¾ NE and fed a high-salt diet (4% NaCl). Blood pressure (BP) was measured in the tail using the cuff method (Sistola, Russia), MCR was assessed using laser Doppler flowmetry (LDF). The reactivity of skin microvessels was assessed by changes in the MCR index before and after iontophoresis of acetylcholine (ACh) and sodium nitroprusside (NP). Based on the assessment of the spectral characteristics of fluctuations in the MCR index obtained using Wavelet analysis, the value of endothelial, neurogenic and myogenic microvascular tone was calculated.Results. 4 months after ¾ NE, rats showed a decrease in the excretory function of the kidneys. In rats on a highsalt diet, an increase in blood urea levels was noted. The blood pressure in rats of the SO+HS group did not significantly differ from the control animals of the SO group (131 ± 8 and 125 ± 4 mmHg, respectively, NS), NE led to a significant increase in blood pressure (135 ± 5 mmHg in rats of the NE group, and 145 ± 7 mmHg – in the NE+HS group). The average MCR was higher in rats receiving a high-salt diet (SO+HS and NE+HS groups), compared with animals of the corresponding group receiving a standard diet. The combination of NE and high-salt load has an inhibitory effect on the amplitude of fluctuations in the intensity of perfusion in all studied ranges: endothelial, neurogenic and myogenic, while the calculated value of skin microvascular tone in three ranges was the highest in NE+HS group rats. In all experimental groups, the reactivity to AH was reduced compared with the SO group, and after NP iontophoresis, the average perfusion rate significantly decreased only in groups of animals receiving a high-salt diet: SO+HS and NE+HS.Conclusion. A high-salt diet in rats with an initial stage of renal dysfunction contributes to an increase in blood pressure and a decrease in natriuresis compared with animals with NE who received a standard diet. With excessive consumption of table salt in rats after NE, the intensity of cutaneous MCR increases, while reducing the variability of the MCR index. A high-salt diet in rats with NE modifies the characteristics of the spectral components of fluctuations in the MCR index, indicating an increase in tonic effects on skin microvessels in the endothelial, neurogenic and myogenic ranges. With hypernatrial load, animals with ¾ NE have a decrease in the reactivity of cutaneous microvessels to AH and NP, which is mediated by both a decrease in endothelial NO production and a decrease in MMC sensitivity to NO.