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E Pintado

Publications and source records attributed to E Pintado.

25 records · Page 2Linked to original sources
PubMed1986

Effects of membrane depolarization and divalent cations on anaphylactic histamine secretion.

The effects of membrane depolarization and divalent cations on histamine release have been studied in sensitized mast cells. Membrane potential of these cells has been measured with intracellular microelectrodes. Our results show that mast cells have a large resting potential (-61 +/- 12 mV) however they do not generate active membrane electrical responses when are depolarized by passing current through the recording microelectrode. High external K+ does not increase histamine release. Histamine secretion is supported by alkali-earth divalent cations (Ca2+ greater than Sr2+ greater than Ba2+) but strongly inhibited by transition metals. Ca2+ concentrations above 1 mM inhibit histamine release, however, this effect is not mimicked by Sr2+ and Ba2+.

Anaphylaxis↗
PubMed1984

Histamine release by pharmacological agents in the absence of external free Ca2+.

The involvement of extracellular free Ca2+ in histamine release was investigated in rat peritoneal mast cells. Incubation of non-antigenized cells in a media with high extracellular potassium did not increase histamine release. Secretion induced by A23187 and compound 48/80 in the presence of Ca2+ requires metabolic energy. In the absence of external free Ca2+ (2.5 microM) histamine release induced by A23187 is reduced but not abolished. Secretion induced by compound 48/80 is independent of extracellular Ca2+. These results lead us to suggest that mast cell plasma membranes probably lack voltage-gated Ca2+ channels and that external Ca2+ may not be an absolute requisite for histamine secretion.

Animals↗
PubMed1983

Parathyroid hormone secretion in the absence of extracellular free Ca2+ and transmembrane Ca2+ influx.

The involvement of extracellular Ca2+ and Ca2+ influx across the plasma membrane in parathyroid hormone (PTH) secretion was investigated in vitro using a new preparation of bovine parathyroid cells. Incubation of these cells in the presence of 25 microM or 2.5 microM free ambient Ca2+ induced a maximal rate of PTH secretion. Low free Ca2+ secretion is not associated with changes in membrane permeability, requires metabolic energy, and is reversible. The Ca2+ channel blocker D600 had no effect on either 45Ca-influx or PTH secretion in these cells. These results, showing that extracellular Ca2+ and Ca2+ influx across the plasma membrane are not required for PTH secretion by parathyroid cells, emphasize the differences in the cellular mechanisms underlying the secretion of PTH vs that of other secretory cells.

Animals↗
PubMed1978

Binding activity regulation of rabbit skeletal muscle adenosine 3'-5'-monophosphate-dependent protein kinases.

A cAMP-dependent protein kinase has been isolated from rabbit muscle and purified. The affinity constant of the enzyme for the nucleotide is Ka = 9.3 X 10(-9) M, with a Vmax = 0.013 X 10(12) moles bound cAMP/1 microgram protein. The influence exerted by different factors is studied: a) Inhibitor (I) of kinase activity: increases the binding capacity for cAMP, by percentages which depend on the amount of I. In the presence of inhibitor (120 microgram/100 microliter) the affinity constant is Ka = 4.1 X 10(-9) M, without change in Vmax. b) Effect of pH: it has a complex influence over binding, being also regulated by cAMP concentration. The positive effect on binding of ionic and bovine serum albumin concentrations, and the negative effect of enzyme preincubation before additions of (H3) cAMP, have also been studied. The importance of these effectors to obtain a high degree of sensitivity in the binding protein method has been assertained.

Animals↗