Pro-contractile role of chloride in arterial smooth muscle: Postnatal decline potentially governed by sympathetic nerves

Acidosis enhances contribution of Ca2+-activated chloride channels to vascular tone regulation in early postnatal period

Introduction

Acidosis often occurs during clinical complications in newborns and can lead to changes in the mechanisms of arterial tone regulation. However, it is unknown how acidosis affects the activity of Ca2+-activated chloride channels (CaCC) in arteries during early ontogenesis. We hypothesized that their activity may increase during acidosis.

Methods

We studied isometric contractions of saphenous arteries isolated from adult and 10-13-day-old rats. Intracellular pH was measured using a fluorescent indicator BCECF-AM simultaneously with recording the contractile activity of the arterial preparation in isometric mode.

Results

Metabolic acidosis with pH = 6.8 caused a significant decrease in the arterial contractile responses of adult and 10-13-day-old rats. The functional contribution of CaCC was absent in the adult rat arteries both at pH = 7.4 and pH = 6.8. However, in 10-13-day-old rat pups, the functional contribution of CaCC was higher at pH = 6.8 compared to pH = 7.4.

Conclusion

Acidosis augments the functional role of CaCC in arteries during early postnatal ontogenesis, but not in adulthood.

Trophic sympathetic influence weakens pro-contractile role of Cl- channels in rat arteries during postnatal maturation

Membrane transporters and their functional contribution in vasculature change during early postnatal development. Here we tested the hypothesis that the contribution of Cl⁻ channels to arterial contraction declines during early postnatal development and this decline is associated with the trophic sympathetic influence. Endothelium‐denuded saphenous arteries from 1- to 2-week-old and 2- to 3-month-old male rats were used. Arterial contraction was assessed in the isometric myograph, in some experiments combined with measurements of membrane potential. mRNA and protein levels were determined by qPCR and Western blot. Sympathectomy was performed by treatment with guanethidine from the first postnatal day until 8–9-week age. Cl⁻ substitution in the solution as well as Cl⁻-channel blockers (MONNA, DIDS) had larger suppressive effect on the methoxamine-induced arterial contraction and methoxamine-induced depolarization of smooth muscle cells in 1- to 2-week-old compared to 2- to 3-month-old rats. Vasculature of younger group demonstrated elevated expression levels of TMEM16A and bestrophin 3. Chronic sympathectomy increased Cl⁻ contribution to arterial contraction in 2-month-old rats that was associated with an increased TMEM16A expression level. Our study demonstrates that contribution of Cl⁻ channels to agonist-induced arterial contraction and depolarization decreases during postnatal development. This postnatal decline is associated with sympathetic nerves development.