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Biomedical subjects

N Chakravarty

Publications and source records attributed to N Chakravarty.

At least 37 records · Page 2Linked to original sources
PubMed1983

Mechanism of histamine release from isolated mast cell granules by calcium with phosphatidyl serine.

Histamine is released from isolated mast cell granules with intact membranes by calcium (10 mM) in presence of phosphatidyl serine (25-50 micrograms/ml). The release occurs both in Krebs-Ringer solution and in sucrose solution without monovalent cations, but the release in Krebs-Ringer solution is somewhat higher. The histamine release is associated with increased calcium uptake. But calcium is taken up much faster, within 5 sec, while it takes several minutes before histamine release is completed. The observations suggest a rapid uptake of calcium to the granule membrane, from which it may be more slowly released to the matrix, displacing histamine from its binding sites. Phosphatidyl serine with calcium could also conceivably change the membrane permeability causing increased influx of sodium ions, thus accounting for the mild enhancement of the release in Krebs-Ringer solution.

Animals↗
PubMed1983

Regeneration of rat mast cells after histamine secretion: changes in histidine decarboxylase activity and heparin synthesis.

Histidine decarboxylase activity in rat peritoneal mast cells is depressed temporarily after histamine secretion induced by antigen in sensitized cells or by compound 48/80. Recovery starts after 10 min. and the enzyme activity is completely restored in about 1-2 hours. There is no stimulation of the enzyme activity upto 4 hours after the exposure to the releaser. The enzyme activity shows more prolonged depression after histamine release induced by inonophore A23187 probably because of leakage of the cytoplasmic enzyme. Inspite of the loss of some granules from the mast cells, histamine uptake is enhanced during the first two hours apparently due to the uptake into the granule matrices in the compound exocytotic vacuoles. These granules remain within the cell, but the release of endogenous histamine to the extracellular fluid during secretion makes the binding sites available for histamine uptake. There is no indication of increased histamine production during the period of observation, viz. up to 6 hours after the secretion. The heparin content is reduced during the first two hours due to the loss of granules from the cells, but this is restored during 4-6 hours by increasing synthetic activity. Heparin synthesis is reduced to about 40% of the normal value during the first 4 hours, and is practically restored to normal during 4-6 hours.

Animals↗
PubMed1982

Histamine release from mast cell granules.

Rat peritoneal mast cells were separated from other cells by differential centrifugation in concentrated serum albumin. Granules were isolated form these cells by ultrasonic disintegration and subsequent centrifugation. 60-80% of the granules had intact membranes and retained their histamine store in a physiological salt solution. Histamine was released from the granules with intact membranes by Ca2+, 10 mM, in the presence of phosphatidyl serine, 25--50 microgram/ml. The release was initiated in 15 sec and completed in 16 min. Other divalent cations in 10 mM concentration, viz. Mg2+, Ba2+, Sr2+, Ni2+ and Mn2+, also released histamine from the granules in the presence of phosphatidyl serine. When histamine release was induced by calcium and phosphatidyl serine the calcium uptake in the granules was remarkably increased. Ca2+ could thus displace histamine from the granule matrix. The possibility that calcium with phosphatidyl serine may change the granule membrane permeability is discussed.

Animals↗
PubMed1981

Electron microscopic study of the regeneration in vitro of rat peritoneal mast cells after histamine secretion.

Regeneration of rat mast cells was studied by TEM from 10 s to 48 h after secretion of histamine induced by compound 48/80. During the first 2 h, small intracellular cavities, formed during compound exocytosis and containing non-membrane-bound remnants of the granules, tended to coalesce, and after 2 h of incubation regeneration started. After 6 h, all the cavities had fused into one large central cavity which contained the remnants of the granules and remained open to the exterior during the entire period. The plasma membrane microfolds which disappeared just after secretion were reformed during regeneration. They were apparently involved in endocytotic-like activity and coated vesicles also appeared beneath the plasmalemma (membrane recycling?). The fate of the granule remnants in the cavity is unknown, as regeneration was not completed after 48 h which is the longest survival time obtained so far in ultrastructural studies of mast cell regeneration in vitro.

Animals↗
PubMed1981

Adenosine triphosphatase in non-secreting and secreting mast cells.

A Ca++-Mg++ ATPase has been demonstrated in the plasma membrane of rat peritoneal mast cells. The enzyme is localized by electron microscopy on the outer surface of the membrane. This agrees with the biochemical findings. A Ca++-Mg++ activated ATPase has also been shown to be present in the granule membrane. The optimal pH of the plasma membrane enzyme is close to the optimal pH for the histamine release. All the 14 inhibitors of plasma membrane ATPase tested - which caused varying degrees of inhibition of the enzyme - also inhibited histamine release induced by antigen, compound 48/80 and the divalent ionophore A23187. The conclusion from the study with the inhibitors is that a mild inhibition of the enzyme is compatible with histamine release, but a pronounced inhibition of the enzyme is always associated with inhibition of histamine release. ATP in low concentrations potentiates the release.

Adenosine Triphosphatases↗
PubMed1980

The role of plasma membrane Ca++-Mg++ activated adenosine triphosphatase of rat mast cells on histamine release.

The role of a Ca++-MG++ activated ATPase, demonstrated on the outer surface of rat peritoneal mast cells, on histamine release induced by antigen (anaphylactic reaction), compound 48/80 and ionophore A23187 has been studied. A high level of the enzyme activity is retained at the optimal pH for histamine release induced by the three releasing agents. The effect of fourteen inhibitors of ATPase has been studied, viz. quinidine, fluoride, platinum salt, suramin, ethacrynic acid, ethyl alcohol, N-ethylmaleimide, Mn++, Ni++, ADP, AMP and the flavones: kaempferol, quercetin, morin. All the inhibitors, which caused varying degrees of inhibition of ATPase, also inhibited histamine release. The inhibition of the enzyme was competitive with ADP, AMP, ethacrynic acid, suramin and morin and non-competitive with the others. The degree of inhibition of ATPase and of histamine release tended to be similar with six inhibitors. With the others the extent of the inhibition of the release and of the enzyme varied. But a marked inhibition of the enzyme was always associated with a pronounced inhibition of histamine release. ATP in lower concentrations (10-20 microM) has been shown to potentiate histamine release induced by all the three releasers, possibly through its utilization by plasma membrane ATPase. The observations agree with the hypothesis that plasma membrane ATPase participates in the histamine release process.

Animals↗
PubMed1975

The utilization of adenosine triphosphate in rat mast cells during histamine release induced by anaphylactic reaction and compound 48/80.

The ATP content of rat peritoneal mast cells has been studied in relation to histamine release induced by compound 48/80 and antigen-antibody (anaphylactic) reaction in vitro. When the ATP content of actively sensitized mast cells was reduced to different levels by oligomycin, a good correlation was obtained between the ATP levels and the amounts of histamine released by the anaphylactic reaction. A similar linear relation has previously been demonstrated between the ATP levels of mast cells and histamine release induced by compound 48/80. The ATP content of mast cells was also studied at different intervals after the exposure of the cells to antigen or compound 48/80. No significant change in the ATP content was observed in untreated mast cells during the short period when histamine release occurs. If, however, the mast cells were preincubated with oligomycin or 2-deoxyglucose to reduce the rate of ATP synthesis while a large part of the histamine release remained unaffected-a decrease in the ATP content could be demonstrated in close time relation to both anaphylactic and compound 48/80-induced histamine release. The observations indicate an increased utilization of ATP in mast cells during the release process.

Adenosine Triphosphate↗