High-Affinity Benzodiazepine Binding Sites on Rat Peritoneal Mast Cells and RBL-1 Cells: Binding Characteristics and Effects on Granule Secretion

SUMMARYAs we have recently shown that GABA should be considered a putative neurotransmitter inSchistosoma mansoni, the present work aimed to search for GABAAreceptors in adult worms using [3H]-flunitrazepam to label the allosteric benzodiazepine binding site which is classically present on GABAAreceptor complexes. We detected a large population (Bmax=8·25±1·1 pmol . mg protein−1) of high affinity (Kd=33·6±1·5 nm) binding sites for flunitrazepam. These sites harboured a singular pharmacological modulation that does not fit well with a mammalian central benzodiazepine receptor, mainly due to a very high affinity for Ro5-4864 and a very low affinity for clonazepam. We also detected a second population of benzodiazepine binding sites labelled with high affinity (IC50=85 nm) by [3H]-PK11195, a selective ligand of the mammalian peripheral benzodiazepine receptor. In conclusion, this work describes the pharmacological properties of a large population of central-like benzodiazepine receptors supporting their study as putative new targets for the development of anti-parasitic agents. We also describe, for the first time, the presence of peripheral benzodiazepine receptors in this parasite.

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Effects of aging on the synthesis of antithrombin-binding sites on heparin chains and heparan sulphate chains in the rat

Biochemical Journal ◽

10.1042/bj3120245 ◽

1995 ◽

Vol 312 (1) ◽

pp. 245-249

Author(s):

A A Horner

Keyword(s):

Mast Cells ◽

Binding Sites ◽

Heparan Sulphate ◽

Significant Decline ◽

Male Rats ◽

High Affinity ◽

Peritoneal Mast Cells ◽

Effects Of Aging ◽

Age Range

[35S]Heparin proteoglycans were isolated from the skins and peritoneal mast cells of male rats aged 2 to 22 months. Their [35S]heparin chains were separated on antithrombin-agarose into fractions with high and low affinities for antithrombin. In skin, the proportion of 35S-labelled high-affinity heparin chains declined from 23% at 2 months to 8% at 12 months and did not change significantly between 12 and 22 months. In peritoneal mast cells, the proportion of 35S-labelled high-affinity heparin chains increased from 14% at 2 months to 21% at 4 months and then did not vary significantly until 15 months of age. By 21 months a consistent and significant decline to 8% occurred. The structures of high-affinity heparin proteoglycans did not change with age. Their decreased proportions, without change in their structure, may indicate that they are produced by a unique subset of mast cells, the proportion of which declines with age. [35S]heparan sulphate chains were isolated from skins and brains of rats in the same age range and fractionated on antithrombin-agarose. There were no significant variations in the proportions of 35S-labelled high-affinity heparan sulphate chains in skin (10%) or brain (24%) between 4 and 22 months of age.

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Presence of a high-affinity Ca2+-and Mg2+-dependent ATPase in rat peritoneal mast-cell membranes

Biochemical Journal ◽

10.1042/bj2260335 ◽

1985 ◽

Vol 226 (1) ◽

pp. 335-338 ◽

Cited By ~ 3

Author(s):

L M Amende ◽

M A Donlon

Keyword(s):

Mast Cell ◽

Mast Cells ◽

Atpase Activity ◽

Cell Membranes ◽

Plasma Membranes ◽

Peritoneal Mast Cell ◽

High Affinity ◽

Dependent Atpase ◽

Peritoneal Mast Cells ◽

Rat Peritoneal Mast Cells

Purified perigranular and plasma membranes isolated from rat peritoneal mast cells were examined for Ca2+- and Mg2+-dependent ATPase activity. Isolated perigranular membranes contained only a low-affinity Ca2+- or Mg2+-dependent ATPase (Km greater than 0.5 mM). The plasma membranes contained both a low-affinity Ca2+- or Mg2+-dependent ATPase (Km = 0.4 mM, Vmax. = 20 nmol of Pi/min per mg), as well as a high-affinity Ca2+- and Mg2+-dependent ATPase (Km = 0.2 microM, Vmax. = 6 nmol of Pi/min per mg).

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Increased density of peripheral benzodiazepine-binding sites in ovarian carcinomas as compared with benign ovarian tumours and normal ovaries

Clinical Science ◽

10.1042/cs0780155 ◽

1990 ◽

Vol 78 (2) ◽

pp. 155-158 ◽

Cited By ~ 71

Author(s):

Yeshayahu Katz ◽

Gilad Ben-Baruch ◽

Yoel Kloog ◽

Joseph Menczer ◽

Moshe Gavish

Keyword(s):

Ovarian Carcinoma ◽

Binding Sites ◽

Ovarian Carcinomas ◽

Binding Characteristics ◽

Normal Tissues ◽

Benign Ovarian Tumours ◽

Benzodiazepine Binding ◽

Ovarian Tumours ◽

Benzodiazepine Binding Sites

1. Benzodiazepines are involved in the control of proliferation and differentiation of normal and malignant cells in vitro. This regulatory ability is probably mediated via peripheral benzodiazepine-binding sites. 2. In the present study we compared the binding characteristics of peripheral benzodiazepine-binding sites in human epithelial ovarian carcinoma with those in benign ovarian tumours and normal ovaries. 3. The affinity and density of peripheral benzodiazepine-binding sites in homogenate preparations of ovarian carcinoma as compared with benign ovarian tumours and with normal tissues (used as controls) were determined using a ligand specific for peripheral benzodiazepine-binding sites, [3H]PK 11195, an isoquinoline carboxamide derivative. 4. We observed a robust (three-to five-fold) increase in the neoplasm compared with benign ovarian tumours and normal tissues, without a concomitant change in affinity values. 5. This finding may reflect a change in the metabolic rates of ovarian cancer which is expressed as the alteration in the density of peripheral benzodiazepine-binding sites.

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