Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the nature of electrophysiological changes in adult cat cardiac ventricular myocytes that may occur when cells are maintained in primary culture for 1-2 wk, the electrophysiology of cells freshly isolated from collagenase-perfused hearts (day 0 controls) was compared with that of cells maintained in primary culture for up to 14 days 1) on a two-dimensional (2D) surface (laminin-coated coverslips), which allowed for changes in cellular morphology, or 2) in a three-dimensional (3D) alginate matrix, which minimized changes in cell shape. Action potentials and whole cell ionic currents were recorded using a conventional whole cell patch technique. Whereas cellular resting potential and the depth of the "notch" terminating phase 1 were diminished relative to controls in 2D- and 3D-cultured cells, the action potential duration and the incidence of early afterdepolarizations (EADs) were increased relative to controls in 2D- but not in 3D-cultured cells. Corresponding alterations in whole cell ionic currents included a 40% reduction in inwardly rectifying K current (IK1) conductance (GK1) and a 90% reduction in transient outward K current (Ito) conductance (Gto) in 2D- and 3D-cultured cells relative to day 0 controls and a 50% increase in L-type Ca current (ICa-L) conductance (GCa-L) in 2D-cultured cells relative to 3D-cultured cells and day 0 controls. The reduction in Gto in long-term culture was half-maximal by days 7 and 8 and could not be attributed to reduced Ito availability, involvement of a noninactivating Ito, the cell culture procedure itself, or the presence of serum in the culture media. Gto was larger in day 0 cells from a heart with right ventricular hypertrophy than in day 0 normal control cells and was reduced subsequent to placement of cells in 3D culture for 19 days. The results suggest that long-term culture and change in cellular morphology can affect the electrophysiology of cardiac ventricular myocytes.
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PMID:Electrophysiology of adult cat cardiac ventricular myocytes: changes during primary culture. 773 21

Cardiomyocytes differentiated in vitro from pluripotent embryonic stem (ES) cells of line D3 via embryo-like aggregates (embryoid bodies) were characterized by the whole-cell patch-clamp technique during the entire differentiation period. Spontaneously contracting cardiomyocytes were enzymatically isolated by collagenase from embryoid body outgrowths of early, intermediate, and terminal differentiation stages. The early differentiated cardiomyocytes exhibited an outwardly rectifying, transient K+ current sensitive to 4-aminopyridine and an inward Ca2+ current but no Na+ current. The Ca2+ current showed all features of L-type Ca2+ current, being highly sensitive to 1,4-dihydropyridines but not to omega-conotoxin. Cardiomyocytes of intermediate stage were characterized by the additional expression of cardiac-specific Na+ current, the delayed K+ current, and If current. Terminally differentiated cardiomyocytes expressed a Ca2+ channel density about three times higher than that of early stage. In addition, two types of inwardly rectifying K+ currents (IK1 and IK,Ach) and the ATP-modulated K+ current were found. During cardiomyocyte differentiation, several distinct cell populations could be distinguished by their sets of ionic channels and typical action potentials presumably representing cardiac tissues with properties of sinus node, atrium, and ventricle. Reverse transcription polymerase chain reaction revealed the transcription of alpha- and beta-cardiac myosin heavy chain (MHC) genes synchronously with the first spontaneous contractions. Transcription of embryonic skeletal MHC gene at intermediate and terminal differentiation stages correlated with the expression of Na+ channels. The selective expression of alpha-cardiac MHC gene in ES cell-derived cardiomyocytes was demonstrated after ES cell transfection of the LacZ construct driven by the alpha-cardiac MHC promoter region followed by ES cell differentiation and beta-galactosidase staining. In conclusion, our data demonstrate that ES cell-derived cardiomyocytes represent a unique model to investigate the early cardiac development and permit pharmacological/toxicological studies in vitro.
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PMID:Cardiomyocytes differentiated in vitro from embryonic stem cells developmentally express cardiac-specific genes and ionic currents. 803 37

Endothelins have been reported to exert a wide range of electrophysiological effects in mammalian cardiac cells. These results are controversial and human data are not available. Our aim was to study the effects of endothelin-1 (ET-1, 8 nmol/l) on the L-type calcium current (ICa-L) and various potassium currents (rapid component of the delayed rectifier, IKr; transient outward current, Ito; and the inward rectifier K current, IK1) in isolated human ventricular cardiomyocytes. Cells were obtained from undiseased donor hearts using collagenase digestion via the segment perfusion technique. The whole-cell configuration of the patch-clamp technique was applied to measure ionic currents at 37 degrees C. ET-1 significantly decreased peak ICa-L from 10.2+/-0.6 to 6.8+/-0.8 pA/pF at +5 mV (66.7% of control, P<0.05, n=5). This reduction of peak current was accompanied by a lengthening of inactivation. The voltage dependence of steady-state activation and inactivation was not altered by ET- 1. IKr, measured as tail current amplitudes at 40 mV, decreased from 0.31+/-0.02 to 0.06+/-0.02 pA/pF (20.3% of control, P<0.05, n=4) after exposure to ET-1. ET-1 failed to change the peak amplitude of Ito, measured at +50 mV (9.3+/-4.6 and 9.0+/-4.4 pA/pF before and after ET-1, respectively), or steady-state IK1 amplitude, measured at the end of a 400-ms hyperpolarization to -100 mV (3.6+/-1.4 and 3.7+/-1.4 pA/pF, n=4). The present results indicate that in undiseased human ventricular myocytes ET-1 inhibits both ICa-L and IKr; however, the degree of suppression of the two currents is different.
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PMID:Effects of endothelin-1 on calcium and potassium currents in undiseased human ventricular myocytes. 1120 54

The ductal system of the exocrine pancreas produces HCO(3)(-)-rich fluid in response to secretin and other stimuli. HCO(3)(-) efflux across the luminal membrane is mediated by a Cl(-)-HCO(3)(-) exchanger operating in parallel with the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. Basolateral K(+) channels provide an exit pathway for K(+) and play a vital role in maintaining the membrane potential, which is a crucial component of the driving force for anion secretion. Measurements of membrane potential with intracellular microelectrodes suggested that Ba(2+)-sensitive K(+) conductance accounts for more than 60% of the total basolateral ionic conductance in resting ducts (1). To identify the Ba(2+)-sensitive K(+) channels, we isolated ducts from normal rat pancreas by collagenase digestion. We first demonstrated that the ducts did not express a vascular endothelial marker PECAM-1 (platelet/endothelial cell adhesion molecule-1), but expressed cytokeratin 20, a marker of duct cells (2), using immunofluorescent staining. In addition, monoclonal anti-CFTR antibody was detected near the luminal membrane of these cells. In cell-attached single-channel recordings, we observed three types of K(+) channels on basolateral membrane in unstimulated duct cells. The 40 pS K(+) channels are likely to mediate whole-cell inwardly rectifying K(+) (Kir) currents, which were blocked by extracellular Ba(2+) in a voltage-dependent manner. The properties of 90 pS and 170 pS K(+) channels are similar to those of Ca(2+)-activated K(+) channels. We then identified Kir2.0 and SK4/IK1 (intermediate conductance Ca(2+)-activated K(+) channel) subunits as molecular candidates of the K(+) channels using RT-PCR analysis. The present results suggest that these subunits may mediate native K(+) currents in resting duct cells. Further functional studies with specific blockers are required to evaluate which of these K(+) channels contribute to the resting membrane potential and might be involved in HCO(3)(-) secretion.
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PMID:K+ channels on resting duct cells from rat pancreas. 2022 23