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PubMed2005

Chloride-sensitive MEQ fluorescence in chick embryo motoneurons following manipulations of chloride and during spontaneous network activity.

Intracellular Cl(-) ([Cl(-)](in)) homeostasis is thought to be an important regulator of spontaneous activity in the spinal cord of the chick embryo. We investigated this idea by visualizing the variations of [Cl(-)](in) in motoneurons retrogradely labeled with the Cl-sensitive dye 6-methoxy-N-ethylquinolinium iodide (MEQ) applied to cut muscle nerves in the isolated E10-E12 spinal cord. This labeling procedure obviated the need for synthesizing the reduced, cell-permeable dihydro-MEQ (DiH-MEQ). The specificity of motoneuron labeling was confirmed using retrograde co-labeling with Texas Red Dextran and immunocytochemistry for choline acetyltransferase (ChAT). In MEQ-labeled motoneurons, the GABA(A) receptor agonist isoguvacine (100 muM) increased somatic and dendritic fluorescence by 7.4 and 16.7%, respectively. The time course of this fluorescence change mirrored that of the depolarization recorded from the axons of the labeled motoneurons. Blockade of the inward Na(+)/K(-)/2Cl(-) co-transporter (NKCC1) with bumetanide (20 microM) or with a low-Na(+) bath solution (12 mM), increased MEQ fluorescence by 5.3 and 11.4%, respectively, consistent with a decrease of [Cl(-)](in). After spontaneous episodes of activity, MEQ fluorescence increased and then declined to the pre-episode level during the interepisode interval. The largest fluorescence changes occurred over motoneuron dendrites (19.7%) with significantly smaller changes (5.2%) over somata. Collectively, these results show that retrogradely loaded MEQ can be used to detect [Cl(-)](in) in motoneurons, that the bumetanide-sensitive NKCC1 co-transporter is at least partially responsible for the elevated [Cl(-)](in) of developing motoneurons, and that dendritic [Cl(-)](in) decreases during spontaneous episodes and recovers during the inter-episode interval, presumably due to the action of NKCC1.

Action Potentials↗
PubMed1984

Energetics of chloride secretion in canine tracheal epithelium. Comparison of the metabolic cost of chloride transport with the metabolic cost of sodium transport.

Canine tracheal epithelium secretes Cl and absorbs Na; the energy for both is derived from the activity of the basolateral membrane Na-K-ATPase. These properties allowed us to examine the energetics of Cl secretion by directly comparing the metabolic cost of Cl transport with the metabolic cost of Na transport. We measured the change in short-circuit current and O2 consumption rate that was produced by a variety of maneuvers that alter Na and/or Cl transport rate. The experimental interventions included the use of the secretagogue epinephrine, the Cl transport inhibitor bumetanide, the Na transport inhibitor amiloride, the Na-K-ATPase inhibitor ouabain, and ion substitutions. The O2 consumption rates required for Na and Cl transport were compared in each individual tissue. The results indicate that the oxygen cost of Cl transport is significantly less than the oxygen cost of Na transport: two to four Cl ions are transported for the same metabolic cost that is required to transport one Na ion. These findings suggest that the basolateral membrane Na-dependent Cl entry step couples the entry of more than one Cl ion to each Na ion.

Amiloride↗
PubMed1989

Differential effects of methylmercuric chloride and mercuric chloride on the histochemistry of rat thyroid peroxidase and the thyroid peroxidase activity of isolated pig thyroid cells.

This study was designed to characterize the interaction of CH3HgCl or HgCl2 with thyroid peroxidase (TPO). Two types of experiments were performed. First, the thyroids from rats that were given 5.6 mg/kg/day of either CH3HgCl or HgCl2 for 2 weeks by intubation were subjected to histochemical treatment and then to electron microscopy. TPO activities in all cell compartments were inhibited by HgCl2 but not by CH3HgCl. Morphological observation showed that taller epithelia were induced by HgCl2, whereas flattened epithelia forming large follicles were induced by CH3HgCl. The serum thyrotropin level was substantially lowered by CH3HgCl but was unchanged by HgCl2. Second, the guaiacol oxidation by TPO in isolated and ruptured pig thyroid cells was spectrophotometrically monitored in the presence of either CH3HgCl or HgCl2. The TPO was not inhibited by CH3HgCl but was inhibited by HgCl2. These results indicated that CH3HgCl induced a hypothyroid state without affecting TPO, whereas HgCl2 inhibited TPO and induced a hypertropic state owing to compensation for loss of enzyme activity, and that the lack of inhibitory activity of CH3HgCl was not due to the inability to penetrate the cells. Therefore, there appeared to be a differential interaction of organic and inorganic forms of mercurials with the thyroid.

3,3'-Diaminobenzidine↗
PubMed1986

Subacute toxicity of methylmercuric chloride and mercuric chloride on mouse thyroid.

Intoxication effect on mouse thyroid by prolonged administration of either CH3HgCl or HgCl2 was studied. It was found by giving CH3 203HgCl and 203HgCl2 through stomach intubation at either a single or a 30 d treatment that thyroid is a moderately susceptible organ to both mercurials. Animals were given 50, 100 and 150 micrograms/d of either mercurial in drinking water for a month. At the lowest amount of HgCl2, body weight was increased, whereas at the highest dose, there was a transient delay in growth. With lower amounts of CH3HgCl, no change in growth was observed. However, at the highest amount, a severe growth inhibition occurred. The thyroid weight was unaffected by lower amounts, but was significantly reduced by 150 micrograms/d of either mercurial. The 24 h radioiodide uptake in the thyroid, expressed by cpm/mg organ weight, was reduced by lower levels of mercurials. CH3HgCl and HgCl2 suppressed the rate of radioiodide incorporation into the iodothyronine fraction, but not into the iodotyrosine fractions, indicating that mercurials do not interfere with organification of iodide but do inhibit the coupling process. Serum thyroxine (T4) level was affected by mercurials, but serum triiodothyronine (T3) was not. This result suggested that even thyroidal secretion of T4 was inhibited by mercurials, but the peripheral conversion of T4 to T3 may not be affected in the maintenance of an active hormone level.

Animals↗
PubMedDate not supplied

Effect of magnesium chloride and guanidinium chloride on the extraction of components of extracellular matrix from chicken cartilage.

In order to evaluate the effect of chaotropic agents on proteoglycan and non-collagenous proteins, chicken xiphoid cartilage was treated with guanidine-HCl and MgCl2 in different concentrations (1M to 5M), and different periods of time (12, 24, 48 and 72 hr). The maximum yield of uronic acid was obtained with 3M MgCl2 (73.3%). Concentrations of 4M and 5M of MgCl2 showed that much less uronic acid was removed, 55.3% and 38.1% respectively. Extraction with 3M MgCl2 and 3M guanidine-HCl resulted better efficiency when performed for 48 hr. Analysis by SDS-PAGE of the extracts obtained with guanidine-HCl and MgCl2 in different concentrations pointed out that most components are equally removed with the two solvents, showing that the extraction with MgCl2 is an alternative assay to remove non-collagenous proteins from extracellular matrix.

Animals↗