Biomedical subjects

A Teti

Publications and source records attributed to A Teti.

At least 55 records · Page 3Linked to original sources

PubMed1997

Human prostatic tumor cells in culture produce growth and differentiation factors active on osteoblasts: a new biological and clinical parameter for prostatic carcinoma.

Prostate cancer (PRCA) cells metastasize to bone with high frequency, inducing typical osteosclerotic lesions. To establish if local stimuli on the bone tissue may derive from metastatic colonies of prostatic origin, we evaluated the biologic activities secreted by human prostatic epithelium and effective on osteoblast-like cells in vitro. Supernatant from short-term tissue cultures of human prostatic tissue samples obtained from PRCA (35 cases) and benign prostatic hyperplasia (BPH, 12 cases) patients were applied to three models of cells with osteoblastic phenotype: two normal [rabbit osteoblasts (OB) and rat periosteal cells (PO)] and one transformed (human osteosarcoma cell line, MG63). Proliferative activity was monitored through enzymatic reduction of tetrazolium salts and expressed as relative mitogenic activities (RMA). Analysis of proliferation and alkaline phosphatase (ALP) activity, a marker of osteoblast function, demonstrates that conditioned media (CM) from PRCA cultures stimulate both growth and activity of osteoblast-like cells to a greater extent compared to CM from BPH. Furthermore, cell growth and activity of osteoblast-like cells are progressively increased by CM derived from patients with stage B (tumor confined within the prostate capsule), stage C (locally invasive tumor), and stage D (invasive tumor with distant metastasis) disease. One of the mechanisms potentially underlying the CM-stimulated effects on bone cells is associated with the urokinase (uPA) enzyme route, whose release progressively increases with the stage of disease. However, antibodies against uPA and p-aminobenzamidine (a low molecular weight urokinase inhibitor) treatment, which both inhibit the proliferative and differentiative effects induced by exogenous urokinase, partially slow down the effects of CM from PRCA tissue cultures, suggesting that additional factors are secreted by prostatic tumor cells in vitro. In conclusion, we show that the mitogenic and differentiative activities for osteoblasts produced by prostatic tumor cells in short-term tissue cultures are related to PRCA stage and may predict the behavior of skeletal metastases in single cases of tumor. In addition, the culture methods used may represent a valid model to study prostatic and bone cellular interactions, which may indicate new therapeutic approaches in metastatic prostate tumors.

Alkaline Phosphatase↗

PubMed1996

pH dependence of neutrophil-endothelial cell adhesion and adhesion molecule expression.

Neutrophil adhesion to the vascular endothelium is enhanced during tissue ischemia and/or inflammation, conditions that are associated with tissue acidosis. This study examined the effects of hypercarbic acidosis (10 or 20% CO2) and of hypocarbic alkalosis (0% CO2) on human neutrophil CD18 and human aortic endothelial cell intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin expression quantified by flow cytometry. Acidosis with 20% CO2 for 4 h decreased ICAM-1 to 60.6 +/- 9.7% of control. In contrast, alkalosis with 0% CO2 for 4 h enhanced ICAM-1 expression to 143.8 +/- 10.1% of control. There was no pH dependence of VCAM-1 or E-selectin expression. Tumor necrosis factor-alpha (TNF-alpha; 10 ng/ml) increased endothelial ICAM-1, E-selectin, and VCAM-1; under these conditions, acidosis with 20% CO2 blunted both ICAM-1 and E-selectin surface expression compared with 5% CO2-, TNF-alpha-treated cells. Hypercarbic acidosis with 20% CO2 increased neutrophil CD18 expression and enhanced neutrophil adhesion. This latter effect was inhibited by neutrophil pretreatment with an anti-CD18 monoclonal antibody. In contrast, when only endothelial cells were preincubated with the hypercarbic buffer, neutrophil adhesion diminished to 55.6 +/- 7.8% of control. The results suggest that acidosis generated during tissue ischemia/inflammation may induce CD18-mediated neutrophil adhesion despite a decrease in ICAM-1 expression.

Cell Adhesion↗

PubMed1996

[Introduction of definite molecular weight heparan sulfate in a protocol of prevention of deep venous thrombosis in prosthetic orthopedic surgery].

Use of definite molecular weight heparan sulphate in a protocol for the prevention of deep venous thrombosis in the total joint replacement surgery. The authors propose a working protocol for the prevention of deep venous thrombosis in prosthetic orthopaedic surgery. It requires that integration of pharmacological, anaesthesiological, rheological and physiokinesitherapic measures, it has permitted a very good prevention of thromboembolic disease and it is well-tolerated and safe. The protocol requires: peripheral anaesthesia (sub-arachnoidal block), pre and post-operative pharmacological treatment with heparan-sulphate of a fixed molecular weight, haemodilution with maintenance of the haematocrit at no more than 30%, early physiokinesitherapy associated with the use of elastic stockings graduated tension. The fifty patients treated with this protocol were controlled during the pre-operative and post-operative stage and one month later and no thrombo-embolic complications resulted.

Aged↗

PubMed1995

Calcitonin increases cytosolic free calcium concentration via capacitative calcium influx.

The calcitonin receptor has been proposed to function as an extracellular Ca2+ concentration ([Ca2+]o) sensor (Stroop, S. D., Thompson, D. L., Kuestner, R. E., and Moore, E. E. (1993) J. Biol. Chem. 268, 19927-19930). To test this hypothesis we studied the LLC-PK1 renal tubular cells and the PC1 cells, a cell line stably transfected with the cloned porcine calcitonin receptor. [Ca2+]i was measured by fura-2 single cell microfluorometry. Addition to the cells equilibrated in 1.25 mM Ca(2+)-containing media of 1-10 mM extracellular Ca2+ did not result in a significant increase of [Ca2+]i. Treatment with 10(-7) M salmon calcitonin (sCT) elicited a rapid, persistent elevation of [Ca2+]i. Addition of 1-10 mM extracellular Ca2+ in the presence of sCT induced a significant [Ca2+]i elevation, about 10-fold that observed in the absence of the hormone. Ca2+ influx was inhibited by lanthanum. The rise of [Ca2+]i at elevated [Ca2+]o was not due to a Ca2+ sensing mechanism with release of Ca2+ from intracellular stores, since it was prolonged, and was not abolished by prior depletion of Ca2+ stores with 10(-6)M thapsigargin. On the contrary, this agent potentiated Ca2+ influx after addition of 1-10 mM Ca2+ by 13-fold versus control. Prior stimulation of [Ca2+]i with 10(-7) M arginine-vasopressin had similar effects, enhancing the subsequent Ca2+ influx. Enhancement of Ca2+ influx by sCT was confirmed by increased Mn2+ quenching of fura-2 fluorescence. In conclusion, arginine-vasopressin or calcitonin enhance Ca2+ influx in LLC-PK1 cells via a Ca2+ release-activated conductance, probably dependent upon capacitative Ca2+ entry. Thus, these effects are not unique to the calcitonin receptor and argue against the receptor functioning as a [Ca2+]o sensor.

Animals↗

PubMed1995

Translocation of protein kinase C isoenzymes by elevated extracellular Ca2+ concentration in cells from a human giant cell tumor of bone.

In this study we investigated the protein kinase C isoenzymes expressed by human osteoclast-like cells harvested from a giant cell tumor of bone (GCT23 cells), and by freshly isolated rat osteoclasts. Immunoblotting analysis revealed that the -alpha, -delta, and -epsilon, PKC isoforms, but not the -beta isoenzyme, are expressed by GCT23 cells. Immunofluorescence studies demonstrated that PKC-alpha, -delta, and -epsilon are homogeneously expressed by both mononuclear and multinucleated GCT23 cells, as well as by rat osteoclasts. Similar to authentic osteoclasts, GCT23 cells responded to an increase of extracellular Ca2+ concentration ([Ca2+]o) with a dose-dependent elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). An increase of [Ca2+]o stimulated the translocation of PKC-alpha from the cytosolic to the particulate fraction, suggesting the involvement of this isoenzyme in the signal transduction mechanism prompted by stimulation of the [Ca2+]o sensing. By contrast, PKC-delta was not altered by exposure to elevated [Ca2+]o, whereas PKC-epsilon underwent reciprocal translocation, disappearing from the insoluble fraction and increasing in the cytosol. The effects of PKC on GCT23 cell functions were investigated by treatment with phorbol 12-myristate, 13-acetate (PMA). We observed that activation of PKC by PMA failed to affect adhesion onto the substrate, but down-regulated the [Ca2+]o-induced [Ca2+]i increases. The latter effect was specific, since it was reversed by treatment with the PKC inhibitors staurosporine and chelerythrine.

Animals↗

PubMed1995

Calcitonin down-regulates immediate cell signals induced in human osteoclast-like cells by the bone sialoprotein-IIA fragment through a postintegrin receptor mechanism.

Calcitonin (CT) is a peptide hormone that interacts with the cAMP-and phospholipase C-associated CT receptor subtypes. We investigated whether CT modulates the interaction of human tumoral osteoclast-like (GCT23) cells with a protein of the bone matrix, bone sialoprotein-II (BSP-II). Single GCT23 cells loaded with the intracellular Ca2+ indicator fura-2 were treated with the maximal active dose (300 micrograms/ml) of the 18-mer Arg-Gly-Asp (RGD)-containing BSP-IIA fragment, and the cytosolic free Ca2+ concentration ([Ca2+]i) was measured by dual wavelength microfluorometry. BSP-IIA stimulated an elevation in [Ca2+]i, consisting mainly of a peak, followed by a rapid return toward baseline. Pretreatment with CT induced a modest elevation of [Ca2+]i. However, CT significantly inhibited the response to BSP-IIA in a dose-dependent manner. Maximal inhibition (90% vs. untreated) was observed in the micromolar range. The intracellular mechanisms leading to this effect were investigated by pretreatment of GCT23 cells with the cAMP permeant analog, (Bu2)cAMP, and the protein kinase-C-activating agent, 12-O-tetradecanoylphorbol 13-acetate. Similar to CT, both agents inhibited the response to 300 micrograms/ml BSP-IIA. The effect induced by CT was specific, because an increase in the extracellular Ca2+ concentration, which is also known to inhibit bone resorption, failed to modify the ability of BSP-IIA to alter [Ca2+]i in GCT23 cells. To investigate whether the CT-induced alteration of BSP-IIA-dependent cell signals was due to a modification in the synthesis of cell surface receptors (integrins) for the extracellular matrix macromolecules, 1-h CT-treated [35S]methionine metabolically labeled GCT23 cell lysates were immunoprecipitated with anti-alpha 3-, -alpha v-, -beta 1-, and -beta 3-integrin subunit antibodies. Autoradiography demonstrated that 10(-7)-10(-6) M CT did not alter new synthesis of the alpha v beta 3 and the alpha 3 beta 1 receptors. Similarly, CT did not affect surface expression of these receptors, assessed by enzyme-linked immunosorbent assay. Finally, no alteration of the adhesion rate and spreading of GCT23 cells onto BSP-IIA-coated substrates was observed. This indicates that CT-induced down-regulation of immediate cell signals prompted by BSP-IIA in GCT23 cells is a postintegrin receptor event.

Animals↗

PubMed1994

New model for bone resorption study in vitro: human osteoclast-like cells from giant cell tumors of bone.

Cells harvested from 12 human giant cell tumors of bone and kept in culture for several passages were characterized for bone-resorbing capability, total and tartrate-resistant acid phosphatase activity, response to the calciotropic hormone calcitonin, cell proliferation, multinucleation after passages, and presence of calcium sensing. Cells obtained from three tumors presented a complete panel of osteoclast characteristics and maintained their multinuclearity after several passages. Cells from four other tumors increased their cAMP levels after treatment with calcitonin, and the other five apparently consisted of cells of stromal origin. These human cell populations with osteoclast characteristics may provide valid in vitro models for the investigation of osteoclastic differentiation and activity.

Acid Phosphatase↗

PubMed1994

Adhesion properties and integrin expression of cultured human osteoclast-like cells.

Osteoclast interaction with extracellular matrix drives the sequential events that end with bone resorption. However, the role of matrix proteins is not yet fully understood. We studied this problem on human osteoclast-like cells derived from giant cell tumors of bone (GCT cells). On GCT cells we considered cytoskeletal organization, adhesion properties, and integrin expression upon plating in serum-free medium onto fibronectin (FN), collagen (COL), thrombospondin (TSP), bone sialoprotein (BSPII), and osteopontin (OPN). GCT cells promptly adhered and spread on FN, BSPII, and OPN, while only 50% adhered on COL and none on TSP. The integrin beta 1 chain was always associated to focal adhesions, while the alpha v beta 3 heterodimer was detected in focal contacts only upon plating on BSPII, OPN, and FN. The focal clustering of beta 1 was impaired by monensin treatment, indicating that endogenous FN secretion was required to drive beta 1 into focal contacts. Conversely, alpha v beta 3 clustering was also not affected by monensin when cells were plated onto plasma FN. Immunoprecipitation of metabolically labeled GCT cell lysates showed that three different heterodimers (alpha v beta 3, alpha 3 beta 1, and alpha 5 beta 1) were assembled. Adhesion to FN was completely inhibited by beta 1 antibodies at dilutions up to 1:400, while beta 3 antibodies, at similar dilutions, impaired spreading but not adhesion. We conclude that alpha v beta 3 is the main integrin used by GCT cells in bone recognition. We also suggest that selected substrata may induce the release and the organization of endogenous FN that eventually drives the recruitment of a beta 1 integrin receptor into focal contacts.

Amino Acid Sequence↗

PubMed1994

Calcium release-activated calcium influx in cultured human mesangial cells.

Ca2+ influx is a major component of the response of cultured human mesangial cells (HMC) to vasoconstrictors. Activators of phospholipase C such as angiotensin II (Ang II) release Ca2+ from intracellular stores and enhance Ca2+ influx, which in turn is modulated by Na+/Ca2+ exchange. By microfluorometry we studied the mechanisms of Ca2+ entry in resting and stimulated fura-2-loaded monolayers or single HMC. Addition of 1 to 10 mM extracellular Ca2+ to cells equilibrated in Ca(2+)-free media resulted in a rapid, persistent elevation of free cytosolic Ca2+ ([Ca2+]i), from 52 +/- 5 to 113 +/- 18 and 226 +/- 37 nM, respectively. Ca2+ influx was blocked by lanthanum or chelation with EGTA, while it was only partially inhibited by voltage-operated Ca2+ channel (VOC) blockers, such as nifedipine or verapamil. The rise of [Ca2+]i at high external [Ca2+] was not due to a Ca(2+)-sensing mechanism with release of intracellular stored Ca2+, since it was prolonged, and it was not seen in cells maintained in normal 1.25 mM [Ca2+] media. Moreover, it was not abolished by prior depletion of Ca2+ stores with 0.5 microM thapsigargin or 5 microM ionomycin in Ca(2+)-free media, which transiently increased [Ca2+]i (to 281 +/- 39 and 380 +/- 51 nM, respectively). On the contrary, both agents markedly potentiated Ca2+ influx upon addition of 1 to 10 mM [Ca2+]e, (to a maximum of 686 +/- 111 and 633 +/- 150 nM, P < 0.05 vs. control).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1994

Extracellular Ca2+ sensing is modulated by pH in human osteoclast-like cells in vitro.

Osteoclasts are polarized cells with a basolateral and an apical membrane exposed to different extracellular Ca2+ ([Ca2+]o) and H+ (pHe) concentrations. Osteoclast bone resorption is inhibited in vitro by increases of [Ca2+]o slightly above physiological levels, detected by a [Ca2+]o sensing causing elevations of the intracellular signal, [Ca2+]i. Nevertheless, during bone resorption the apical membrane is exposed to [Ca2+]o severalfold higher than physiological without apparent inhibition of osteoclast functions. Because pHe facing the apical membrane is acidic, in this single-cell [Ca2+]i and intracellular pH study we addressed the question of whether the responses of human osteoclast-like cells from a giant cell tumor of bone to elevated [Ca2+]o are altered by reducing pHe. We first observed that low pHe stimulated Ca2+ efflux and cell acidification. We then demonstrated that the amplitude of the [Ca2+]o-dependent [Ca2+]i "spikes" is downregulated by low pHe, with approximately 70-fold higher [Ca2+]o required to induce significant responses at pHe 6.0 compared with pHe 7.4. Similar downregulation was observed in authentic freshly isolated rat osteoclasts. Finally, we observed that occupancy of the [Ca2+]o sensing by Ca2+ prompted rapid and transient cell acidification partially counteracted by a Na(+)-dependent amiloride derivative-sensitive H+ transport. These results demonstrate that the cascade of events triggered by activation of the [Ca2+]o sensing is affected by environmental pH and in turn influences cellular H+ transport. Such pH-related features of the [Ca2+] o sensing mechanism might be relevant for the regulation of osteoclast-like function.

Calcium↗

PubMed1994

Activation of inositol phospholipid turnover and calcium signaling in rat Sertoli cells by P2-purinergic receptors: modulation of follicle-stimulating hormone responses.

To study the role of extracellular nucleotides in the regulation of Sertoli cells, the effects of ATP and its analogs on the Ca(2+)-phospholipid- and cAMP-dependent pathways were tested. Cultured Sertoli cells from immature animals were incubated with ATP or structurally related compounds, and phosphoinositide (PI) turnover or cAMP accumulation was measured. Among the several nucleotide phosphate analogs tested, adenosine 5'-O-(3-thiotriphosphate) was the agonist most potent in stimulating inositol phosphate accumulation. The effects of purine nucleotides on PI turnover were time and concentration dependent. Because nonhydrolizable ATP analogs also stimulated PI turnover, ATP metabolites or metabolic products are not responsible for the observed stimulation. The order of potency of the different ATP analogs [adenosine 5'-O-(3-thiotriphosphate) > ATP approximately equal to UTP > beta, gamma-methyleneadenosine 5'-triphosphate, 2-methylthio-ATP > adenosine] was consistent with the presence of P2U receptors (nucleotide receptors) on the surface of the Sertoli cell. Augmented PI turnover was accompanied by a transient increase in Ca2+ concentration, measured in single Sertoli cells loaded with the intracellular Ca2+ indicator fura-2. When used alone, ATP and its analogs did not have a direct effect on cAMP levels in the Sertoli cell. However, ATP or its analogs inhibited FSH-dependent cAMP accumulation by more than 70%. Purine nucleotides also efficiently blocked the effects of FSH distal to cAMP accumulation, because extracellular ATP completely reversed the changes in Sertoli cell shape induced by FSH. The nucleotide-dependent inhibition of cAMP accumulation was blocked by pertussis toxin to a different degree depending on the purine or pirimidine nucleotide used. This indicated that more than one mechanism contributes to the purine nucleotide-dependent inhibition of cAMP accumulation. These data provide evidence that purine nucleotide receptors coupled to multiple pathways are present on the Sertoli cell in culture, and that extracellular ATP has profound biological effects on the FSH responsiveness of the Sertoli cell.

Adenosine↗

PubMed1993

Binding of osteopontin to the osteoclast integrin alpha v beta 3.

Occupancy of the chicken osteoclast alpha v beta 3 integrin stimulates immediate cell signals. Peptides from osteopontin containing Arg-Gly-Asp and peptides from the osteopontin and bone sialoprotein sequences containing Arg-Gly-Asp stimulated immediate reductions in osteoclast cytosolic Ca2+. The changes in cytosolic Ca2+ required the Arg-Gly-Asp sequence, and were blocked by LM609, a monoclonal antibody to the alpha v beta 3 integrin. Osteoclast stimulation by the proteins through the integrin did not require immobilization since soluble peptides produced changes in cytosolic Ca2+ and inhibited osteoclast binding to bone particles and bone resorption. The decrease in cytosolic Ca2+ stimulated by osteopontin and related peptides was due to activation of a plasma membrane Ca(2+)-ATPase. Thus, the data suggest that ligand binding to the osteoclast alpha v beta 3 integrin results in a reduction in cytosolic Ca2+ which participates in regulation of osteoclast function.

Animals↗

PubMed1993

Animal models of bone physiology.

Because of the well-known technical difficulties in investigating the histology and physiology of the skeleton, bone physiology is not yet completely understood. Much new information has been obtained in recent years with in vitro investigations, but animal models are widely used when the overall effects of hormones or therapeutic agents or both need to be investigated. In this review, we discuss results obtained over the past year on several not yet completely understood topics. The effect of exercise on bone mass has been stressed by several authors, and at the cellular level, it has been suggested that the inositol cascade is the intracellular transduction pathway for mechanical stimuli. Ovariectomized rat systems have been widely used to demonstrate the protective effect of estrogen against bone resorption, and interesting indications of an estrogen-dependent stimulation of bone formation have been presented. The anabolic effect of low doses of fluoride has also been assessed.

Animals↗

PubMed1993

Chronic staphylococcal osteomyelitis: a new experimental rat model.

A rat model of chronic staphylococcal osteomyelitis was developed. Fibrin glue (5 microliters) and Staphylococcus aureus (2 x 10(6) CFU/5 microliters) were inoculated into the proximal metaphysis of the tibia. The rats were killed at intervals of between 1 and 6 months, and the tibias were removed. Induced lesions were evaluated by radiographic, macroscopic, and histological examinations and bacterial counts. Roentgenograms revealed osteomyelitis in more than 90% of the tibias. Gross bone pathology revealed skeletal deformation, new bone formation, abscesses, and draining skin fistulas in more than 80% of cases. Histological examination revealed osteomyelitis in more than 90% of cases, and bacterial counts were positive in 86% of cases. Only fibrin glue (5 microliters) was inoculated into controls. Controls showed no osteomyelitic lesions, and counts were negative in seven of eight control tibias. The main feature of this model is the use of fibrin glue instead of the sclerosing agents and foreign bodies used in other models. The model reproduces lesions similar to those of human posttraumatic osteomyelitis and can be reliably used in pathophysiological and therapeutic studies.

Animals↗

PubMed1993

Transduction of arginine vasopressin signal in skeletal myogenic cells.

Arginine vasopressin (AVP) induced concentration-dependent (10(-9) to 10(-6) M) stimulation of inositol phosphate production and a biphasic increment of cytosolic free Ca2+ concentration ([Ca2+]i) in skeletal myogenic cells in culture. These effects were almost completely abolished when the cells were pretreated with the AVP antagonist [deamino-Pen1,Val4,D-Arg8]-vasopressin before stimulation with AVP, thus confirming a V1 receptor-mediated effect. Inositol 1,4,5-trisphosphate production was maximally stimulated within 2-3 s of treatment with AVP, immediately followed by release of Ca2+ from intracellular deposits. Both effects were inhibited by treatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA). Such effect of TPA was reversed by the protein kinase C inhibitor staurosporine. Vasopressin also regulated the intracellular pH of responsive cells with mechanisms involving both Na+ and anion transport across the plasma membrane. However, unlike in other cell types, AVP stimulated the Na(+)-H+ antiport only simultaneously with a dramatic cell acidification or after treatment with TPA. Response to AVP was observed in L6 and L5 and, to a lesser extent, in chick embryo myogenic cells, regardless of the stage of differentiation (myoblast or myotube). Comparison of different subclones of the L6 cell line demonstrated that the responsiveness to AVP correlated positively with their myogenic potential.

Animals↗

PubMed1993

Immediate cell signal by bone-related peptides in human osteoclast-like cells.

We tested whether recognition of bone-related peptides regulates intracellular Ca2+ concentration ([Ca2+]i) of giant cell tumor of bone (GCT). [Ca2+]i was measured in single cells by fura 2 fluorometry. GCT cells were sensitive to bone sialoprotein-II (BSP-II), osteopontin (OPN), and related fragments. Responses consisted of a prompt increase of [Ca2+]i, mostly transient, with a peak followed by a rapid return toward baseline. Responses were not mimicked by bovine plasma fibronectin. Sensitivity of GCT cells to bone peptides was specific, since BALB/3T3 fibroblasts and U-937 histiocytic lymphoma cells with monocytic phenotype failed to respond to BSP-II and OPN fragments. GRGDSP synthetic esapeptide, carrying the Arg-Gly-Asp adhesive motif, and GRGESP (Asp replaced by Glu), but not the GRADSP (Gly replaced by Ala), were active in inducing [Ca2+]i transients as well. Responses were observed also in cells treated with the BSP-II 1C fragment, lacking any known adhesive sequence, indicating that the active peptides inducing [Ca2+]i increments may be multiple. Sensitivity to extracellular matrix peptides was present in a variable fraction of the cells and was downregulated on long-term culture. The mechanism inducing [Ca2+]i elevations was mostly related to Ca2+ release from thapsigargin-sensitive intracellular pools.

3T3 Cells↗

PubMed1993

Rat testicular myoid cells respond to endothelin: characterization of binding and signal transduction pathway.

The presence of endothelin (ET), a vasoconstrictor peptide, in the testis suggests that it may regulate nonvascular target cells. We investigated binding ability, regulation of inositol phosphate metabolism, changes in cytosolic free Ca2+ concentrations ([Ca2+]i), and induction of morphological changes by ET-1 in rat primary testicular myoid cell cultures. ET-1 specifically bound to highly purified rat testicular myoid cells in a time- and temperature-dependent manner. Scatchard analysis of the binding studies indicated the presence of a single class of high affinity binding sites, with an apparent Kd of 3 x 10(-10) M and a maximal binding capacity of 10(5) sites/cell. ET-1 induced both rapid production of inositol triphosphate and mobilization of [Ca2+]i in a concentration-dependent fashion. By contrast, inositol lipid metabolism was slightly affected by ET-1 in the total peritubular cell population. Purified Sertoli cells failed to show either ET-1 binding or ET-1-induced phosphatidylinositol hydrolysis. Mobilization of [Ca2+]i mostly depended upon the release of Ca2+ from thapsigargin-sensitive intracellular Ca2+, whereas it was not affected by abolishment of the Ca2+ gradient through the plasma membrane or by inhibition of L-type voltage-sensitive Ca(2+)-channels by nifedipine. These findings together with the fact that Sertoli cells are unable to respond to and bind ET-1 indicate that ET is a specific agonist of myoid cells in the seminiferous tubule and suggest a role for ET-1 in the autocrine/paracrine regulation of testicular function.

Animals↗

PubMed1993

Human osteoclast-like cells recognize laminin via an RGD independent mechanism.

Interactions between cells from human giant cell tumors of bone and the extracellular matrix protein laminin were studied. Cells were capable of recognizing this substratum via a RGD-independent mechanism. Recognition induces adhesion and spreading onto laminin. This protein triggered the release of cellular FN which in turn enhanced recruitment of the beta 1 chain-containing integrin receptor.

Amino Acid Sequence↗