Facilitated hyperpolarization signaling in vascular smooth muscle-overexpressing TRIC-A channels.

The TRIC channel subtypes, namely TRIC-A and TRIC-B, are intracellular monovalent cation-specific channels and likely mediate counterion movements to support efficient Ca(2+) release from the sarco/endoplasmic reticulum. Vascular smooth muscle cells (VSMCs) contain both TRIC subtypes and two Ca(2+) release mechanisms; incidental opening of ryanodine receptors (RyRs) generates local Ca(2+) sparks to induce hyperpolarization and relaxation, whereas agonist-induced activation of inositol trisphosphate receptors produces global Ca(2+) transients causing contraction. Tric-a knock-out mice develop hypertension due to insufficient RyR-mediated Ca(2+) sparks in VSMCs. Here we describe transgenic mice overexpressing TRIC-A channels under the control of a smooth muscle cell-specific promoter. The transgenic mice developed congenital hypotension. In Tric-a-overexpressing VSMCs from the transgenic mice, the resting membrane potential decreased because RyR-mediated Ca(2+) sparks were facilitated and cell surface Ca(2+)-dependent K(+) channels were hyperactivated. Under such hyperpolarized conditions, L-type Ca(2+) channels were inactivated, and thus, the resting intracellular Ca(2+) levels were reduced in Tric-a-overexpressing VSMCs. Moreover, Tric-a overexpression impaired inositol trisphosphate-sensitive stores to diminish agonist-induced Ca(2+) signaling in VSMCs. These altered features likely reduced vascular tonus leading to the hypotensive phenotype. Our Tric-a-transgenic mice together with Tric-a knock-out mice indicate that TRIC-A channel density in VSMCs is responsible for controlling basal blood pressure at the whole-animal level.

[TRIC channel and hypertension].

TRIC channel subtypes form bullet-shaped homo-trimeric assemblies and behave as K (+) channels in intracellular membrane systems. The pathophysiological defects observed in knockout mice suggest that TRIC channels mediate counter-K (+) movements to facilitate Ca(2 +) release from intracellular stores in various cell types. In vascular smooth muscle cells (VSMCs) , Ca(2 +) release mediated by ryanodine receptors (RyRs) generates local Ca(2 +) sparks, which activate cell-surface Ca(2 +) -dependent K (+) channels and induce hyperpolarization. Tric-a-knockout mice develop hypertension due to elevated resting tonus in the mutant VSMCs. In Tric-a-knockout VSMCs, RyR-mediated Ca(2 +) sparks are compromised and the hyperpolarization signaling is thus impaired. Under such depolarized conditions, voltage-dependent L-type Ca(2 +) channels are hyper-activated to enhance resting tonus in Tric-a-knockout VSMCs. Therefore, the expression level of TRIC-A channels in VSMCs seems to set resting blood pressure at whole animal level. Moreover, our association study identified several single nucleotide polymorphisms (SNPs) around the TRIC-A gene that increase a hypertension risk and restrict the efficiency of antihypertensive drugs. The observations suggest that the TRIC-A SNPs can provide biomarkers for the diagnosis and personalized medical treatment of essential hypertension.

Selective determination of diphenhydramine in compound pharmaceutical containing ephedrine by flow-injection electrochemiluminescence.

On the basis of the structural interactions between diphenhydramine (DPH) and ephedrine (EPH) to enhance electrochemiluminescence (ECL) intensity, a flow-injection ECL analysis of DPH in the present of EPH by utilizing tris(2,2'-bipyridine)ruthenium(II), (Ru(bpy)(3)2+) has been reported. In the optimized experimental conditions, the linear ECL response to concentrations of DPH is from 2.00 to 40.0 microg/L with a correlation coefficient of 0.9995 and a detection limit of 1.20 microg/L. The relative standard deviation (RSD) was less than 4.6% (n=5) and the recovery was in the range of 98-106% for the determination of DPH in pharmaceutical samples. The method avoids any interference of coexistent EPH in the compounding drug without prior separation. The method has advantages over HPLC method in terms of speed and convenience, economics and safe procedure, and could be an alternative for places where HPLC equipment is not available.