Merck

Functional properties of submucosal venules in the rat stomach.

Pflugers Archiv : European journal of physiology (2014-07-30)
Retsu Mitsui, Hikaru Hashitani
ABSTRACT

Venules in the stomach may have intrinsic properties for maintaining active microcirculation drainage even during gastric filling. Properties of spontaneous and nerve-mediated activity of submucosal venules in the rat stomach were investigated. Changes in vasodiameter and intracellular Ca(2+) in venular smooth muscle cells (SMCs) were monitored by video tracking and Fluo-8 Ca(2+) imaging, respectively. Venular SMCs developed synchronous spontaneous Ca(2+) transients and corresponding rhythmic constrictions of the venules. Nominally Ca(2+)-free solution or an L-type Ca(2+) channel blocker (1 μM nifedipine) disrupted the Ca(2+) transient synchrony and abolished spontaneous constrictions. Spontaneous constrictions were also prevented by inhibitors of sarcoplasmic reticulum Ca(2+)-ATPase (10 μM cyclopiazonic acid (CPA)), IP3 receptors (100 μM 2-APB) or Ca(2+)-activated Cl(-) channels (100 μM niflumic acid). Transmural nerve stimulation (TNS) induced a long-lasting venular constriction that was abolished by α-adrenoceptor antagonist (1 μM phentolamine), while TNS evoked a sympathetic transient constriction of arterioles that was abolished by a combination of phentolamine and a P2 purinoceptor antagonist (10 μM pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS)). Consistently, P2X1 purinoceptor immunoreactivity was detected in arteriolar but not venular SMCs. Primary afferent nerve stimulation (300 nM capsaicin) caused a venular dilatation by releasing calcitonin gene-related peptide. Thus, Ca(2+) release from the sarcoplasmic reticulum may play a fundamental role in the generation of spontaneous Ca(2+) transients, while electrical coupling amongst venular SMCs via L-type Ca(2+) channel activation appears to be critical for Ca(2+) transient synchrony as well as spontaneous contractions. Sympathetic venular constrictions appear to be exclusively mediated by noradrenaline due to the lack of P2X1 receptor in venular SMCs.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Caffeine, SAJ special grade, ≥98.5%
Sigma-Aldrich
DL-Tyrosine, 99%
Sigma-Aldrich
Caffeine, meets USP testing specifications, anhydrous
Sigma-Aldrich
Caffeine, Sigma Reference Standard, vial of 250 mg
Sigma-Aldrich
Caffeine, BioXtra
Sigma-Aldrich
Caffeine, powder, ReagentPlus®
Sigma-Aldrich
4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid disodium salt hydrate, ≥80% (elemental analysis), powder
Sigma-Aldrich
N6-Cyclopentyladenosine, solid
Sigma-Aldrich
Niflumic acid
Sigma-Aldrich
2-Aminoethyl diphenylborinate, 97%
Sigma-Aldrich
Caffeine, anhydrous, 99%, FCC, FG
Sigma-Aldrich
Tetracaine, meets USP testing specifications
Sigma-Aldrich
Tetracaine, ≥98% (TLC)
Sigma-Aldrich
Nifedipine, ≥98% (HPLC), powder
Sigma-Aldrich
Cyclopiazonic acid from Penicillium cyclopium, ≥98% (HPLC), powder
Sigma-Aldrich
Capsaicin, ≥95%, from Capsicum sp.
Sigma-Aldrich
Capsaicin, natural
Sigma-Aldrich
Capsaicin, from Capsicum sp., ≥50% (HPLC)