Na+/Ca2+ Exchanger 1/2 Double-Heterozygote Knockout Mice Display Increased Nitric Oxide Component and Altered Colonic Motility

Abstract

Abstract. The Na + /Ca 2+ exchanger (NCX) is a plasma membrane transporter involved in regulating intracellular Ca 2+ concentrations. NCX is critical for Ca 2+ regulation in cardiac muscle, vascular smooth muscle, and nerve fibers. To determine the role of NCX1 and NCX2 in gastrointestinal tissues, we examined electric field stimulation (EFS)-induced responses in the longitudinal smooth muscle of the distal colon in NCX1 and NCX2 double-heterozygote knockout mice (Double HET). We found that the amplitudes of EFS-induced relaxation that persisted during EFS were greater in Double HET than in wild-type mice (WT). Under the non-adrenergic, noncholinergic (NANC) condition, EFS-induced relaxation in Double HET was similar in amplitude to that of WT. In the experiments in which l-NNA was added under NANC conditions following the EFS, the magnitudes of EFS-induced relaxation were smaller in Double HET than those in WT. In addition, an NCX inhibitor, SN-6, enhanced EFS-induced relaxation but did not affect EFS-induced relaxation under NANC condition, as in Double HET. Moreover, the magnitudes of relaxation induced by NOR-1, which generates NO, were greater in Double HET compared with WT. Similarly, SN-6 potentiated the magnitudes of NOR-1-induced relaxation. In this study, we demonstrate that NCX regulate colonic motility by altering the sensitivity of the inhibitory component.

Evidence that Nitric Oxide Is a Non-Adrenergic Non-Cholinergic Inhibitory Neurotransmitter in the Circular Muscle of the Mouse Distal Colon: A Study on the Mechanism of Nitric Oxide-Induced Relaxation

“…Following this equilibration period, the strips were exposed to EFS with trains of 100 pulses of 0.5 ms, 30 V, and 10 Hz for 10 s to evoke smooth muscle contraction and relaxation. When the NANC responses were recorded, atropine (1 μmol/l) and guanethidine (5 μmol/l) were used to block the cholinergic responses and exclude the adrenergic responses, respectively [21,22]. Preparations of L-NNA, SnPP-IX, MRS2179, α-chymotrypsin, ODQ, ryanodine, thapsigargin, apamin, ChTX, and iberiotoxin were directly added to the bath at least 10 min prior to each experiment for testing.…”

Na+/Ca2+ exchanger‐heterozygote knockout mice display increased relaxation in gastric fundus and accelerated gastric transit in vivo

“…Immunofluorescent staining for whole-mount preparations was performed as described previously with some modifications. 20,21 Briefly, the fundus obtained from WT was washed in Tyrode's solution. The segments were fixed with 4% paraformaldehyde for 2 h at 4°C.…”

Roles of Na+/Ca2+ exchanger isoforms NCX1 and NCX2 in motility in mouse ileum

“…Immunofluorescent staining Nishiyama K. et al | 8 Immunofluorescent staining on frozen sections was performed as previously described (Azuma et al, 2008) with some modifications (Nishiyama et al, 2013). Immunoreactivity of NCX1 and NCX2 was detected using an Alexa Fluor 488 -labeled goat anti-rabbit IgG antibody.…”