Biomedical subjects

M R Carson

Publications and source records attributed to M R Carson.

4 recordsLinked to original sources

PubMed1992

Histamine, actin-gelsolin binding, and polyphosphoinositides in human umbilical vein endothelial cells.

Histamine activates inositol phospholipid metabolism, increases calcium, and causes a change in shape of human umbilical vein endothelial (HUVE) cells. Changes in endothelial cell shape are determined, in part, by changes in the actin cytoskeleton. Gelsolin is an actin-binding protein with the potential to alter the actin cytoskeleton in response to changes in cell calcium and/or changes in polyphosphoinositides. Therefore, we examined the interactions of actin and gelsolin in HUVE cells in which inositol phospholipid metabolism was activated with histamine. In HUVE cells exposed to histamine we estimated actin-gelsolin binding by quantitating actin and gelsolin, immunoprecipitated with anti-gelsolin Sepharose. We estimated the relative amount of filamentous actin in the histamine-exposed HUVE cells by quantitating the amount of actin that was Triton soluble. We also measured the amount of phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) in the HUVE cells before and after exposure to histamine. We found that histamine decreased the amount of actin that was immunoprecipitated with gelsolin, decreased the fraction of cell actin that was Triton soluble, and increased PIP and PIP2. These results demonstrate that histamine promotes actin filament formation in HUVE cells and that histamine-mediated changes in actin-gelsolin binding in these cells are better predicted by changes in polyphosphoinositides than by increases in cell calcium.

Actins↗

PubMed1992

Mastoparan activates apical chloride and potassium conductances, decreases cell volume, and increases permeability of cultured epithelial cell monolayers.

Mastoparan is a tetradecapeptide. Mastoparan added to the apical surface of monolayers of Madin-Darby canine kidney (MDCK) epithelial cells, cultured on micropore filters, activated ion transport and increased the permeability of the paracellular pathway across the monolayers. In monolayers of similar MDCK cells in which the basolateral membrane was permeabilized with Staphylococcus aureus alpha toxin (Staph. alpha toxin), the effects of mastoparan on apical membrane ion conductances were dependent on the presence of guanosine triphosphate (GTP). Mastoparan and GTP increased apical membrane chloride conductance more than potassium conductance, with very little change in sodium conductance. In intact monolayers, addition of barium to the apical bath prevented mastoparan activation of ion transport and the increase in paracellular permeability. Increasing bath potassium to 130 mM also reduced ion transport and prevented the increase in paracellular permeability. We hypothesized that these observations could be linked by mastoparan activation of apical chloride and potassium conductances, with consequent decreases in cell volume and resultant increases in paracellular permeability. Addition of 270 mM mannitol to isosmotic media to decrease cell volume decreased MDCK monolayer transepithelial resistance. Addition of mastoparan to monolayers of MDCK cells grown on micropore filters decreased cell volume to the same extent as addition of 270 mM mannitol to isosmotic media. Addition of the potassium channel inhibitor, barium, prevented the decrease in cell volume in response to mastoparan. Mastoparan activates apical membrane chloride and potassium conductances in MDCK cells. The loss of these ions from the cells decreases cell volume, and the decrease in cell volume increases the permeability of the paracellular pathway.

Animals↗

PubMed1989

Histamine and inositol phosphate accumulation in endothelium: cAMP and a G protein.

Histamine increases microvascular permeability through a calcium-dependent process, and histamine occupancy of the H1-receptor increases calcium in cultured endothelial cells. Agents that increase adenosine 3',5'-cyclic monophosphate (cAMP) in endothelial cells prevent the in vivo increase in microvascular permeability that follows histamine exposure. In the current experiments, histamine occupancy of the H1-receptor increased the flux of albumin across monolayers of cultured human umbilical vein endothelial cells (HUVEC). This was prevented by pretreating the cells with theophylline, forskolin, and 8-bromo-cAMP (BrcAMP), which also decreased the flux of albumin across control monolayers. Exposing the cells to histamine increased inositol phosphate accumulation in the cells, and this was prevented by the H1-antagonist pyrilamine but not by theophylline, forskolin, and BrcAMP. Exposing the cells to histamine increased intracellular calcium measured with fura-2. The increase in cell calcium was prevented by pyrilamine but not by pretreatment with theophylline, forskolin, and BrcAMP. When endogenous cell GTP was depleted by permeabilizing the membranes of the endothelial cells with Staphylococcus aureus alpha-toxin, histamine-stimulated inositol phosphate accumulation was enhanced with addition of GTP but not with addition of GDP to the buffer. Addition of GTP alone to the buffer did not increase inositol phosphate accumulation in alpha-toxin-treated cells. Histamine stimulates inositol phosphate accumulation in HUVEC via a G protein. Inhibition of the edemagenic effects of histamine by cAMP does not occur by interrupting this signal transduction pathway between the binding of histamine to its receptor and the increase in intracellular calcium.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1987

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Ambulatory Care↗