Effect of exogenous heparin on secretory status of rat mast cells under immobilization stress]

The significant increase of heparin release from mast cells was observed in rats under stress conditions induced by 60 min immobilization. The index of its saturation with heparin became 4 times lower. The highest secretory activity of mast cells was observed during the first 30 min of immobilization. It was shown that at that time the heparin release from mast cells occurred by granulolysis (merocrine type of secretion). In the rats received heparin (15 or 150 u/200 g) during the first 15 min of immobilization the mast cells released heparin with the same intensity as in a 4 control animals. But then in rats with high heparin blood concentration the heparin release from mast cells ceased and mast cells began to accumulate heparin from blood. By the 30th min of immobilization the heparin content in the mast cells has become normal.     

Effect of non-fractionated and low-molecular heparin on the functional state of mast cells]

The state of the mast-cell population of rats treated with unfractionated and low-molecular weight heparins under stress conditions has been comparatively studied by the morphometrical assay. The stress was produced by 60 min immobilization followed by intravenous injection of unfractionated (UF) or low-molecular weight (LMW) heparin. The stress-induced heparin release from mast cells resulted in a 3.3-fold decrease of the index of saturation with heparin and in a significant increase of granulolysis and degranulation. The mast cell secretory status reached the preinjection level within 20 min in rats with UF heparin injected (15 unit/200 g). At the same time mast cells of rats with LMW heparin have no such ability. The data obtained indicate that LMW heparin in contrast to UF heparin cannot be accumulated (or accumulated very slowly) by mast cells. This fact as well as low affinity of LMW heparin to endothelium and blood platelets promote its preservation in blood for a long time.     

Decreased sensitivity to the hypoglycemic action of insulin in animals with a lowered blood heparin concentration

It has been shown that in animals with reduced heparin blood concentration the hypoglycemic insulin action was considerably low. This was established for rats with alloxan diabetes and ageing rats with depressed anticoagulation system and atherosclerosis enhanced by prolonged atherogenic diet. With insulin injection (0.2-0.3 U/200 g), blood sugar concentration in such animals was 2-2.5 times lower than in normal ones. The compensation of endogenous heparin deficiency by an intravenous injection of heparin normalizes the reaction of animals to exogenous insulin.     

Changes in numbers and heparin content of peritoneal fluid mast cells of growing rats measured by flow cytofluorometry

A cytofluorometric method, based on berberine staining of mast cell heparin, was used for flow cytofluorometric counting and heparin quantitation of mast cells in crude peritoneal suspensions of growing rats. The automatic flow cytofluorometric counting of mast cells correlated well with hemocytometer cell counts. The mean mast cell heparin content obtained by flow cytofluorometry showed good agreement with such obtained by cytofluorometry of microscopically identified mast cells. The number of peritoneal mast cells and the mean mast cell heparin content was found to increase as the animals grew older. The results of the microscope fluorometric measurements suggested that the heparin content was normally distributed within mast cell populations of both young and old rats. However, the heparin distributions obtained by flow cytofluorometry were often positively skewed but did not fulfill the condition of the log-normal distribution.     

Protein content,dry mass and chemical composition of individual mast cells related to body growth

Summary Recently developed quantitative microscopical techniques were used to study relations between body growth and protein content as well as dry mass of individual mast cells. Since previous studies had shown an age-related increase of mast cell content of 5-hydroxytryptamine (5-HT) and heparin, these mast cell components were also included in the present study. The cells were obtained from the peritoneal cavity of rats aged 44–269 days (body weights 189–610 g). All studied mast cell parameters showed an increase that was related to the growth of the animals. The dry mass increased 60%, protein 50%, heparin 50% but 5-HT increased as much as 260% during the studied growth period. There was a mutual and linear correlation between all studied mast cell parameters. Population studies, based on large scale measurements of individual mast cells from young and adult rats, were made. These studies showed that histograms of 5-HT content, protein content and dry mass of individual mast cells were skewed with a tail towards higher values and approximately lognormal. On the other hand, the frequency distribution of heparin content of individual mast cells was approximately normal.Supported by grants from the Swedish Medical Research Council, Project no 2235     

Protein content, dry mass and chemical composition of individual mast cells related to body growth.

Recently developed quantitative microscopical techniques were used to study relations between body growth and protein content as well as dry mass of individual mast cells. Since previous studies had shown an age-related increase of mast cell content of 5-hydroxytryptamine (5-HT) and heparin, these mast cell components were also included in the present study. The cells were obtained from the peritoneal cavity of rats aged 44--269 days (body weights 189--610 g). All studied mast cell parameters showed an increase that was related to the growth of the animals. The dry mass increased 60%, protein 50%, heparin 50% but 5-HT increased as much as 260% during the studied growth period. There was a mutual and linear correlation between all studied mast cell parameters. Population studies, based on large scale measurements of individual mast cells from young and adult rats, were made. These studies showed that histograms of 5-HT content, protein content and dry mass of individual mast cells were skewed with a tail towards higher values and approximately lognormal. On the other hand, the frequency distribution of heparin content of individual mast cells was approximately normal.     

Heparin secretion by mast cells as an index of the status of the anticoagulant system

The status of the mast cell population was studied and compared after administration of trypsin or alpha-thrombin in similar molar concentrations. Morphometry disclosed a substantial shift of the mast cell population towards light, heparin-free cells within one minute after alpha-thrombin administration. The index of mast cell saturation with heparin dropped below 1. The maximal heparin secretion was observed at the 5th minute of experiment. The morphometric criteria of the mast cell population returned to basal level in 120 minutes. These data along with a significant increase in the level of complex heparin compounds and plasma thrombin time indicate heparin release as a result of the effector action of the anticoagulation system. No changes were observed in the activity of complex heparin compounds and in thrombin time after intravenous injection of trypsin. It is suggested that high heparin secretion by mast cells may serve as criterion of the active status of the anticoagulation system.     

Heparin potentiates in vivo neutrophil migration induced by IL-8

Chemokine IL-8 attracts neutrophils by a haptotactic gradient, made possible by its interaction with proteoglycans of the extracellular matrix. Heparan sulfate, but not heparin, potentiates the attraction exerted in vitro by IL-8. In the present study we first confirmed this in vitro phenomenon, observing that IL-8 activity was potentiated 100% by heparan sulfate, but not by heparin. Then, we evaluated the interference of heparan sulfate or heparin on in vivo neutrophil migration induced by IL-8. The activity of rat IL-8 (3.5 g/animal) preincubated with heparan sulfate (50 g/animal) or heparin (77 g/animal) was assayed on the rat dorsal air pouch. Contrary to in vitro experiments, heparin, but not heparan sulfate, potentiated the in vivo IL-8 activity two-fold. We investigated the relationship between this observation and that reported by others, that IL-8-induced migration depends on the presence of mast cells, which contain heparin-rich granules. We studied the neutrophil migration induced by IL-8 (3.5 g/animal) into the rat peritoneal cavity depleted of mast cells. Neutrophil migration was reduced by 32% when compared to that observed in normal animals. The response of depleted rats was reconstituted by preincubation of IL-8 with heparin (77 g/animal). These data suggest that heparin released from cytoplasmic granules may be the contribution of mast cells to IL-8-induced neutrophil migration.     

Histochemical heterogeneity of dermal mast cells in athymic and normal rats

Summary Mucosal mast cells (MMC) and connective tissue mast cells (CTMC) of the rat contain different proteoglycans, which can be distinguished using histochemical methods. The chondroitin sulphate proteoglycan of the MMC, unlike the heparin of the CTMC, does not show fluorescent berberine binding, is susceptible to aldehyde fixatives and stains preferentially with Alcian Blue in a staining sequence with Safranin. The majority of the dermal mast cells are typical CTMC and are located in the deep part of the dermis. Subepidermal mast cells are comparatively few in normal rats but numerous in athymic rats and mice. These cells differ from other dermal mast cells in that they stain preferentially with Alcian Blue and they appear to contain little histamine. We examined some of the histochemical properties of the skin mast cells of female PVG-rnu/rnu rats and their heterozygous littermates aged from 5 to 29 weeks. The thiazine dye-binding of the subepidermal mast cells was partially blocked by formaldehyde fixation and only about half of them showed a weakly fluorescent berberine binding. The critical electrolyte concentration of the Alcian Blue staining of the subepidermal mast cells was between that of CTMC and MMC. Deaminative cleavage with nitrous acid abolished the staining of all skin mast cells, while that of the MMC was unaffected. There were no statistically significant differences in the staining patterns of the dermal mast cells between different ages or groups of rat. These results indicate that the subepidermal mast cells contain a heparin proteoglycan which is, however, different from that of the typical CTMC of other sites. They thus appear to represent a second example of a mast cell within a defined anatomical location exhibiting a distinct proteoglycan expression.     

Role of heparin in realization of the hypoglycaemic action of insulin

A temporary resistance to the hypoglycaemic action of insulin has been found after preliminary binding of heparin in the blood of animals by 1 mg/200 of protamine sulphate (PS). This effect was observed after 5-30 min PS treatment before the insulin injection or endogenous increase of insulin stimulated by sugar load. PS did not influence the concentration of immunoreactive insulin in blood plasma. 2,5-ionene, a synthetic antagonist of heparin, induced temporary resistance to the hypoglycaemic action of insulin. Intravenous injection of heparin in corresponding doses after PS administration restored the hypoglycaemic effect of insulin. The results suggest that the presence in the circulation of reactive heparin may be necessary for insulin reception by the target tissue.     

Modulation of the mitotic activity and population of the mast cells in the oral mucosa by substance P

To assess the effect of substances inducing mast cell degranulation (substance P and granuliberin R) on the mitotic indices of the gingiva stratified epithelium, basal cells from rats were studied in vivo. Seventy Lewis male rats were used in the study. The rats received injections of either 0.1 ml 0.9% NaCl (l0 rats), or substance P (10(-4), l0(-6), 10(-8) g/ml) (30 rats), or granuliberin R (10(-4), l0(-6), 10(-8) g/ml) (30 rats) into their mandibular gingiva in the vicinity of the right mental foramen. The mitotic index of keratinocytes was established after the kolchicine arrest (2 hours prior to material collection i.p. injection). The number of cells in metaphase was counted on 1000 consecutive basal layer cells after hematoxilin and eosin section staining. Mast cells were revealed using pinocyanol erythrosinate according to Bensley. Numerical density and morphometric features were analyzed. Substance P and granuliberin R injected into the gingiva affect the mast cells and the basal cell proliferation of the gingival epithelium. The diminished mitotic activity of basal layer cells was accompanied by degranulation and/or migration of mast cells under the basal membrane of the epithelium. After administration of high doses of granuloliberin R, mast cells were found in the deep connective tissue alligned towards the epithelium. A neuromediator from the trigeminal nerve (substance P) and substances from mast cells actively interfere in the proliferation of oral keratinocytes and the activity of connective tissue cells.     

The role of mast cells in vascular permeability disorders in rats subjected to immobilization stress]

Disturbances of vascular permeability were studied by the "vascular labeling" technique in the mesentry during the 24-hour immobilization of rats. Administration of dimebolin (an antihistaminic preparation) decreased the number of labeled vessels and labeling intensity. This effect was expressed in the presence of mast cells only and was accompanied by the mast cell degranulation. The authors suppose that the mast cells contain a substance preventing the disturbance of vascular permeability and released during degranulation. Such substance might be heparin. Experiments showed that small doses of heparin failed to produce such effect. These results allowed one to conclude that mast cells played a double role in the mechanisms of disturbance of vascular permeability during immobilization--the damaging (by the action of histamine and serotonine) and the protective (by the released heparin) action.     

Cytofluorometric quantitation of 5-hydroxytryptamine and heparin in individual mast cell granules.

Cytofluorometric quantitation of 5-hydroxytryptamine (5-HT) and heparin in individual mast cell granules is described. The technique is based on micromanipulation of intact mast cells reacted with formaldehyde or stained with Berberine sulfate and the use of a cytofluorometer equipped with a sensitive peak detecting device. The quantities of 5-HT and heparin contained in mast cell granules which are of the order of 10(-16) and 10(-13) g, respectively were expressed as relative fluorescence guanta. The results of measurements on representative samples of mast cell granules indicate that all granules contain heparin as well as 5-HT, and that there are large variations in both 5-HT and heparin content within the granule populations of individual cells. A dose dependent increase in 5-HT content in both cells and individual mast cell granules occurred 24 hr after the injection of 10--50 mg L-5-hydroxytryptophan/kg intraperitoneally. There was no evidence for an increase in the heparin content of granules or cells, indicating that a new synthesis of granular macromolecules is not required for the 5-HT uptake. The results further suggest that 5-HT may be stored initially in a cytoplasmic extragranular pool and then taken up in the mast cell granules.     

Enhanced serum glucocorticoid levels mediate the reduction of serosal mast cell numbers in diabetic rats.

Rats turned diabetic by treatment with alloxan exhibit a significant reduction in serosal mast cell numbersin parallel with decreased insulin levels in the plasma. Our aim was to investigate the putative involvement of endogenous glucocorticoid hormone in this phenomenon. The findings indicated that rats treated with alloxan responded with an increase in levels of serum corticosterone concomitantly with decreased mast cell numbers in the pleural space. We found that either surgical bilateral adrenalectomy or pretreatment with the steroid antagonist RU 486 (20 mg/kg, i.p.) impaired the drop in pleural mast cell counts in alloxinated rats. Administration of insulin (15 U/kg) prevented the increase in corticosterone levels and restored pleural mast cell levels in diabetic animals. In addition, treatment of naive rats with corticosterone (0.5 mg/kg, s.c.) or dexamethasone (0.1 mg/kg, s.c.), for 3 consecutive days, led to a reduction in the number of mast cells recovered from the pleural cavity as noted in diabetic animals. In contrast, insulin reduced serum corticosterone levels and induced a significant elevation in pleural mast cell numbers in naive rats. We conclude that there is a causative relationship between increased levels of glucocorticoids and down-regulation of mast cell numbers associated with the diabetic state, both phenomena clearly sensitive to insulin.     

Elevation of plasma triglyceride levels due to 2-deoxy-D-glucose in conscious rats

Hypertriglyceridemia due to 2-deoxy-D-glucose administration was observed in conscious rats. Plasma triglyceride levels were elevated dose-dependently 2 or 3 hrs after administration of 2-deoxy-D-glucose (5-40 mg/100 g body weight). Prior to the rises in triglyceride, plasma epinephrine levels were elevated rapidly, whereas plasma insulin was not increased depspite continuous hyperglycemia. Elevation of plasma triglyceride was suppressed by addition of phentolamine, whereby insulin release was remarkably enhanced. Plasma lipoprotein lipase release by heparin infusion was significantly suppressed 2 hr after 2-deoxy-D-glucose administration. In conclusion, it is suggested that the hypertriglyceridemic effect of 2-deoxy-D-glucose may be mediated by decreased clearance of endogeneous lipoprotein particles (mostly chylomicrons) attributable to a lowered lipoprotein lipase activity.     

Morphological and functional characteristics of peritoneal mast cells from young rats

To study why neonatal and young rats are resistant to the effects of some secretagogues, such as compound 48/80 and 2.5-S nerve growth factor, we examined peritoneal mast cells from 14–15-day-old rats (young rats) and compared them to peritoneal mast cells from adults. Peritoneal mast cells from young rats contain approximately one-tenth of the amount of histamine observed in adult peritoneal mast cells. However, both cell populations contained similar low levels of the mucosal mast cell-associated protease rat mast cell protease II. Histochemical analysis of peritoneal mast cells from young rats using safranin O and berberine sulphate suggested that only a portion of the granules of these cells contained heparin. At an ultrastructural level the young rat peritoneal mast cell contains relatively few granules. The majority of mast cells from young rats have a bilobed or indented nucleus which is only rarely observed in adult cells. Functionally, the young rat peritoneal mast cell demonstrates a significantly reduced histamine release in response to the connective tissue mast cellspecific secretagogues compound 48/80 and 2.5-S nerve growth factor. In contrast, the percent histamine release in response to the neurotransmitter substance P, which degranulates both connective tissue mast cells and intestinal mucosal mast cells, was similar in the adult cells and the young rat cells. This study demonstrates substantial differences between the young rat and adult peritoneal mast cells which may explain the ability of very young animals to withstand large doses of certain secretagogues.     

Heparin modulates the growth and adherence and augments the growth-inhibitory action of TNF-alpha on cultured human keratinocytes

Previous works suggest the involvement of mast cells in the epithelialization of chronic wounds. Since heparin is a major mediator stored in the secretory granules of mast cells, the purpose of this work was to elucidate the function of heparin in epithelialization using in vitro culture models. For this, low- and high-calcium media in monolayer and epithelium cultures of keratinocytes were used. Also, an assay based on keratinocyte adherence onto plastic surface was used as well. Heparin (0.02-200 microg/ml) inhibited keratinocyte growth in a non-cytotoxic and dose-dependent manner in low- and high-calcium media, Keratinocyte-SFM and DMEM, in the absence of growth factors and serum. Also, heparin inhibited the growth of keratinocyte epithelium in the presence of 10% fetal calf serum and DMEM. Instead, in the presence of Keratinocyte-SFM and growth factors, heparin at 2 microg/ml inhibited the growth by 18% but at higher heparin concentrations the inhibition was reversed to baseline. TNF-alpha is another preformed mediator in mast cell granules and it inhibited keratinocyte growth in monolayer and epithelium cultures. Interestingly, heparin at 2-20 microg/ml augmented or even potentiated this growth-inhibitory effect of TNF-alpha. The association of TNF-alpha with heparin was shown by demonstrating that TNF-alpha bound tightly to heparin-Sepharose chromatographic material. However, heparin could not augment TNF-alpha-induced cell cycle arrest at G0/G1 phase or intercellular adhesion molecule-1 expression in keratinocytes. In the cell adherence assay, heparin at 2 microg/ml inhibited significantly by 12-13% or 33% the adherence of keratinocytes onto the plastic surface coated with fibronectin or collagen, respectively, but this inhibition was reversed back to baseline at 20 or 200 microg/ml heparin. Also, heparin affected the cell membrane rather than the protein coat on the plastic surface. In conclusion, heparin not only inhibits or modulates keratinocyte growth and adherence but it also binds and potentiates the growth-inhibitory function of TNF-alpha.     

Effect of the medicinal leech salivary gland secretion on the state of rat subcutaneous mast cells

It is firstly showed that the medicinal leech salivary gland secretion (SGS) as a polycomponent system of proteins and low-molecular weight substances, activates rat subcutaneous mast cells in vitro prompting a decrease in the heparin saturation index and increasing some characteristic mast cells morphometric parameters. The same mast cell changes were detected by analysis of some specimens of subcutaneous cellular tissue in the point of skin injured by the leech bite. It is shown that these changes are saved during 3 days. The mechanical injury of rat skin does not effect the mast cells activation. Activation of mast cells by SGS is extended to the distant subcutaneous mast cells. It is expressed in sharp decreasing of heparin saturation index although not statistically positive. The secondary leeching on these distant points provokes reduction of mast cells activation and some decrease of post-leeching blood heparin content: 0.154 +/- 0.03 units/ml (n = 10) as compared with post-leeching blood heparin contents analysed from the wound after the primary leeching (0.160 +/- 0.03 units/ml, n = 10). Proceeding from these findings, participation of heparin secreted from activated mast cells in the support of post-leeching bleeding is suggested, the phenomenon which provides unloading of capillary pool by application of medicinal leeches for treatment many diseases.     

The blood anticoagulant system in rats perorally administered a heparin-acetylsalicylic acid complex]

Heparin/acetylsalicylate complexes (1:9 and 10:1) were obtained in vitro. Single or chronic (7-8 days) per os administration to white rats of 0.1% solution of the heparin/acetylsalicylate complex (0.3 ml/200 g body weight) enhanced anticoagulative properties of blood plasma, increased the fibrinolytic activity in respect of stabilized fibrin, and diminished the thrombin-induced platelet aggregation.     

Subcellular localization of brain mast cell histamine in developing rat

The intracerebroventricular administration of compound 48/80 or polymixin B to rats 0 to 60 days old, produced a decrease both in the histamine which sediments in the crude nuclear fraction, as well as in the number of mast cells in the brain. In contrast, the histamine-releasers did not affect histamine levels in subcellular fractions where neuronal histamine is found. Once released, histamine disappeared rapidly (t 1/2 = 3.8 min). In untreated animals and in those treated with histamine releasers, the number of mast cells/g in the whole brains of developing rats and in the cerebral regions of adult rats showed a close correlation with the histamine levels in the crude nuclear fraction. The content of histamine per mast cell in adult rat brain was estimated to be about 13 pg/cell. Histologic examination of the subcellular fractions revealed the presence of intact mast cells in the crude nuclear fraction obtained from untreated animals, and of degranulated mast cells in the same fraction obtained from animals treated with histamine releasers. The mast cell contribution to adult rat brain histamine levels was about 22%. Our results strongly support that most of the histamine which sediments in the crude nuclear fraction of the rat brain is located in mast cells. Determination of histamine in the crude nuclear fraction and in the supernatant of this fraction is proposed as an easy way for identifying the cellular pool altered by any treatment affecting brain histamine levels.