Assuntos
Soro Antilinfocitário/farmacologia , Aorta/fisiologia , Regulação da Expressão Gênica , Fígado/fisiologia , Preservação de Órgãos/métodos , Hormônios Peptídicos/genética , Veia Porta/fisiologia , Adenosina/farmacologia , Alopurinol/farmacologia , Animais , Sequência de Bases , Primers do DNA , Regulação da Expressão Gênica/efeitos dos fármacos , Glutationa/farmacologia , Humanos , Insulina/farmacologia , Fígado/efeitos dos fármacos , Masculino , Soluções para Preservação de Órgãos/farmacologia , Proteína Relacionada ao Hormônio Paratireóideo , Rafinose/farmacologia , Ratos , Ratos Endogâmicos Lew , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Tempo , Coleta de Tecidos e Órgãos/métodos , Transcrição Gênica/efeitos dos fármacosRESUMO
The present experiments examined the potential ability of parathyroid hormone-related protein (PTHrP) to influence growth of the human colon cancer cell HT-29 and the ability of the cell to adhere to several extracellular matrix (ECM) proteins found in normal tissues. Addition of PTHrP analogs, PTHrP (1-34), PTHrP (67-86), or PTHrP (107-139), to HT-29 cells in culture did not influence cell growth or the adhesion of the cells to wells coated with fibronectin, laminin, or collagen type I. Likewise, in HT-29 cells induced to overexpress PTHrP by stable transfection with PTHrP cDNA, compared to vector-transfected control HT-29 cells, no effect on cell growth occurred. However, in the transfected cells, the increased production of PTHrP significantly enhanced cell adhesion to type I collagen but not to fibronectin or laminin. The results raise the possibility that PTHrP might play a role in colon tumor invasion and metastasis by influencing cell adhesion to specific extracellular matrix proteins.
Assuntos
Adesão Celular , Colágeno Tipo I/metabolismo , Neoplasias do Colo/patologia , Proteínas/metabolismo , Proteínas/fisiologia , Adesão Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Neoplasias do Colo/metabolismo , Matriz Extracelular/metabolismo , Fibronectinas/metabolismo , Células HT29 , Humanos , Laminina/metabolismo , Metástase Neoplásica , Proteína Relacionada ao Hormônio Paratireóideo , Fragmentos de Peptídeos/farmacologia , Proteínas/genética , Proteínas/farmacologia , TransfecçãoRESUMO
The rat intestinal cell line, IEC-6, was used as a model to study effects of parathyroid hormone-related protein (PTHrP) on crypt cell growth. Studies showed that addition of PTHrP analogs (1-34), (67-86), or (107-139) to growth medium did not affect proliferation of cells grown in either high (10% Nu-Serum) or low serum (1% Nu-Serum). However, studies on clonal lines of IEC-6 cells stably transfected with PTHrP cDNA and overexpressing PTHrP showed that increased PTHrP production enhanced cell growth and 3H-thymidine incorporation in high, but not low, serum. Additional studies examined the role of the nuclear localization sequence (NLS) of PTHrP in mediating the growth effect. In three clonal IEC-6 lines transfected with PTHrP cDNA bearing a mutated NLS, the ability of PTHrP to stimulate 3H-thymidine incorporation and cell growth was lost. The results suggest that endogenously produced PTHrP can promote proliferation of IEC-6 cells and that the integrity of the NLS of PTHrP is required for its growth effects.
Assuntos
Biossíntese de Proteínas , Proteínas/genética , Animais , Divisão Celular/genética , Linhagem Celular , Vetores Genéticos/síntese química , Humanos , Sinais de Localização Nuclear/genética , Proteína Relacionada ao Hormônio Paratireóideo , Fragmentos de Peptídeos/farmacologia , Proteínas/farmacologia , Proteínas/fisiologia , Ratos , Deleção de Sequência/genética , TransfecçãoRESUMO
We used the rat intestinal cell line, IEC-6, to study potential effects of overexpression of PTH-related protein (PTHrP) on apoptosis. A clonal line of PTHrP-overexpressing cells was established by stably transfecting parental cells with PTHrP complementary DNA in a sense orientation (sense). A similarly transfected line stably, transfected with empty vector, served as control (vector). Immunoreactive PTHrP, measured in culture medium, showed that sense cells secreted approximately 30 times as much PTHrP as did vector control cells. Apoptosis induced by serum withdrawal was evaluated by several methods. DNA laddering was demonstrable in sense-transfected cells as early as 12 h after serum withdrawal but not until later time points in vector-transfected control cells. Flow cytometric analysis of propidium iodide-stained cells showed a greater increase in the sub-G1 (apoptotic) population in sense cells, compared with vector. Fluorescent microscopy with Hoechst 33258 dye showed increased nuclear fragmentation and condensation in sense cells. Studies of apoptotic gene expression by ribonuclease protection assay, and protein by Western blot analysis, showed an enhanced ratio of Bax to Bcl-x(L) in sense cells. Mutation of the PTHrP nuclear localization amino acid sequence negated the ability of PTHrP to enhance apoptosis.
Assuntos
Apoptose , Intestinos/citologia , Proteínas/fisiologia , Animais , Linhagem Celular , Mutação , Sinais de Localização Nuclear/fisiologia , Proteína Relacionada ao Hormônio Paratireóideo , Proteínas Proto-Oncogênicas c-bcl-2/biossíntese , Ratos , TransfecçãoRESUMO
We have utilized clonal lines of the rat osteoblastic cell line ROS 17/2.8 stably transfected with full-length parathyroid hormone-related protein (PTHrP) cDNA in a sense or an antisense orientation to examine the effects of alteration in the production of endogenous PTHrP on expression of the PTH/PTHrP receptor. In the stably transfected clonal cell lines, changes in PTH/PTHrP receptor expression were evaluated by Northern blot analysis, whole-cell ligand binding of 125I-[Tyr36] PTHrP (1-36), and exogenous PTHrP (1-34)-stimulated cyclic adenosine monophosphate (cAMP) accumulation. Compared to control (vector-transfected) cells, PTHP-overproducing (sense-transfected) cells exhibited a marked decrease in the expression of PTH/PTHrP receptor mRNA and PTHrP ligand binding, as well as a corresponding decrease in the PTHrP (1-34)-stimulated cAMP response. By contrast, the antisense-transfected cells showed a marked increase in expression of PTH/PTHrP receptor mRNA and PTHrP (1-34) ligand binding, but a significant increase in the PTHrP (1-34)-stimulated cAMP response was not detected. Using antisense-transfected ROS cells, PTH/PTHrP receptor mRNA expression and 125I-[Tyr36] PTHrP (1-36) binding were downregulated by treatment for 24 h with exogenous PTHrP (1-36), forskolin, or dibutyryl cAMP. The findings extend those of earlier studies showing receptor downregulation by exogenous PTH by indicating that endogenous PTHrP, as well as circulating PTH, may help regulate receptor production; and suggesting that even very low concentrations of the peptide may influence receptor production.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Osteossarcoma/metabolismo , Proteínas/farmacologia , Receptores de Hormônios Paratireóideos/genética , Animais , Northern Blotting , Bucladesina/farmacologia , Colforsina/farmacologia , AMP Cíclico/metabolismo , Humanos , Osteoblastos/metabolismo , Proteína Relacionada ao Hormônio Paratireóideo , Proteínas/genética , Proteínas/metabolismo , RNA Antissenso/análise , RNA Mensageiro/análise , Ratos , Receptores de Hormônios Paratireóideos/metabolismo , Transfecção , Células Tumorais CultivadasRESUMO
To investigate potential effects of endogenous parathyroid hormone-related peptide (PTHrP) on osteoblast function, ROS 17/2.8 cells were transfected with full-length PTHrP cDNA in a sense or antisense orientation to alter PTHrP production. Compared with vector-transfected control cells, PTHrP-overproducing (sense-transfected) cells showed increased DNA synthesis ([(3)H]-thymidine incorporation) and increased growth (cell number). The extent of apoptosis was compared for the different clones using the terminal deoxynucleotide-mediated dUTP nick-end-labeling assay (TUNEL) and Hoechst staining. No differences in percentages of apoptotic cells were found under basal culture conditions or after 3 days of serum deprivation, which, itself, markedly increased numbers of apoptotic cells. The effect of PTHrP on osteoblast differentiation was assessed by examining two protein markers of differentiation, alkaline phosphatase, and bone morphogenetic protein (BMP)-2. Alkaline phosphatase activity was decreased in sense-transfected cells and increased in antisense-transfected cells, compared with cells transfected with empty vector. PTHrP-overproducing cells also showed decreased numbers of BMP-2-positive cells, whereas antisense-transfected cells showed no difference compared with vector control. The results indicate that: (a) endogenously produced PTHrP can increase growth of these osteoblastic cells by stimulating proliferation while not affecting apoptosis; and (b) the increased cell proliferation produced by PTHrP was accompanied by a reduction in activity or amount of two proteins normally expressed by differentiated osteoblasts.
Assuntos
Diferenciação Celular/fisiologia , Divisão Celular/fisiologia , Osteoblastos/citologia , Proteínas/fisiologia , Fator de Crescimento Transformador beta , Fosfatase Alcalina/metabolismo , Apoptose/fisiologia , Sequência de Bases , Proteína Morfogenética Óssea 2 , Proteínas Morfogenéticas Ósseas/metabolismo , Linhagem Celular , Primers do DNA , Replicação do DNA/fisiologia , Marcação In Situ das Extremidades Cortadas , Osteoblastos/enzimologia , Osteoblastos/metabolismo , Proteína Relacionada ao Hormônio Paratireóideo , Proteínas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , TransfecçãoRESUMO
Infusion of insulin directly into thyroid arterial blood perfusing the surgically isolated in situ pig thyroid gland produced an increase in the secretion rate of calcitonin (CT) measured by immunoassay in thyroid venous effluent blood. Insulin in concentrations ranging from approximately 1 to 400 ng/ml produced a maximal stimulation of 4-5 fold. The stimulatory effect of insulin on CT could not be duplicated by infusion of either IGF-I or amylin. Specific binding of radiolabeled insulin was demonstrated using isolated pig thyroid plasma membranes and both rat (6-23) and human (TT) medullary thyroid carcinoma C-cells. Increased CT release was observed from C-cells exposed to a high concentration of insulin. The administration of glucose iv to pigs in order to stimulate secretion of endogenous insulin produced an increase in circulating insulin, which was accompanied by an increase in the secretion of CT. The results show that insulin, delivered directly to the pig thyroid gland, can stimulate CT release. The in vitro binding and secretion studies indicate that C-cells can bind insulin and respond with an increase in CT secretion, and the iv glucose experiments suggest that endogenous insulin is capable of stimulating CT secretion. The findings imply that insulin is capable of acting as a CT secretagogue and suggest that changes in CT secretion may accompany altered states of insulin production such as diabetes or insulin-secreting tumors.
Assuntos
Calcitonina/metabolismo , Hipoglicemiantes/farmacologia , Insulina/farmacologia , Glândula Tireoide/efeitos dos fármacos , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Células Cultivadas , Glucose/farmacologia , Humanos , Injeções Intravenosas , Ratos , Taxa Secretória/efeitos dos fármacos , Estimulação Química , Suínos , Porco Miniatura , Glândula Tireoide/metabolismo , Glândula Tireoide/ultraestrutura , Células Tumorais CultivadasRESUMO
Following the signal observation that contact with positively charged dextran resin (PCDR) inhibited the growth of cultured mammary (Hs578T and MDA-MB-231), pancreatic (H2T), and myeloma (RR-658) tumor cell lines, studies were developed in the hamster cheek pouch model using hamster H2T pancreatic tumor cells to determine if the antiproliferative effect of PCDR could inhibit tumorigenesis. In these studies, the control population represented groups injected with H2T cells alone or in combination with either neutral or negatively charged resin. When cells (5 x 10(2) to 1 x 10(5)) and PCDR were administered simultaneously, the tumor incidence (percent engraftment) and growth of tumors that already had been established were significantly reduced. When PCDR was injected into already established 1-35-mm2 H2T tumors (engraftment for 21 days = 96%), the resin suppressed the growth of the smallest tumors (< 10 mm2). In none of these trials was the somatic growth of the host hamsters affected. PCDR contact with H2T cells in vitro for 4 days or used to treat growing solid tumors for 72 days significantly reduced cellular ornithine decarboxylase activity. While the mechanism of PCDR action has not been established, the observations have implications for in vivo tumor therapeutic models.
Assuntos
Materiais Biocompatíveis/farmacologia , Resinas de Troca de Cátion/farmacologia , Dextranos/farmacologia , Neoplasias Experimentais/prevenção & controle , Animais , Resinas de Troca Aniônica/química , Resinas de Troca Aniônica/farmacologia , Materiais Biocompatíveis/química , Resinas de Troca de Cátion/química , Bochecha , Cricetinae , Dextranos/química , Masculino , Teste de Materiais , Mesocricetus , Transplante de Neoplasias , Neoplasias Experimentais/enzimologia , Neoplasias Experimentais/patologia , Ornitina Descarboxilase/metabolismo , Neoplasias Pancreáticas/enzimologia , Neoplasias Pancreáticas/patologia , Neoplasias Pancreáticas/prevenção & controle , Células Tumorais CultivadasRESUMO
OBJECTIVE: The increasing proportion of medical students whose primary language is other than English and recent reports of poor communication skills of medical graduates has generated community concern about the methods of selection of students and their communication skills training. This paper examines the relationship between language background and examination performance in oral communication skills in Year 5 medical students. METHOD: Questionnaire data from all Year 5 students in the 1992 general practice terms were matched to examination results. RESULTS: Seventy percent of students responded. Most students whose primary language was not English passed, although some required remedial communication skills tuition. The most powerful predictors of poor performance were recent arrival in Australia and living in an environment where English was not spoken at home. CONCLUSION: Students with poor English oral communication skills should be encouraged to speak English away from the medical school and should be offered additional tuition so that their skills in other languages are not lost to the health-care system.
Assuntos
Competência Clínica/normas , Comunicação , Emigração e Imigração , Etnicidade , Idioma , Relações Médico-Paciente , Estudantes de Medicina/psicologia , Adulto , Austrália , Medicina de Família e Comunidade/educação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Características de Residência , Critérios de Admissão Escolar , Inquéritos e QuestionáriosRESUMO
A well differentiated human hepatoma cell line (Hep G2) was used to explore potential roles for PTH-related peptide (PTHrP) as an autocrine/paracrine growth factor. Using Northern analysis or reverse transcription-PCR, Hep G2 cells were found to express messenger RNAs for both PTHrP and the cloned PTH/PTHrP receptor, and the cells exhibited specific binding for [125I]PTHrP(1-36). Hep G2 growth medium was found to contain relatively large amounts of immunoreactive PTHrP (30 vs. 1-2 pM in medium not exposed to cells), and the PTHrP in growth medium (conditioned medium) was shown to contain N-terminal PTHrP biological activity, as assessed by the ability of the medium to stimulate cAMP production in rat osteosarcoma cells (ROS 17/2.8). Conditioned medium produced a dose-dependent severalfold increase in ROS cell cAMP that could be blocked by the PTHrP receptor antagonist [Asn10,Leu11,DTrp12]PTHrP-(7-34). PTHrP in Hep G2 cells also was detected by immunocytochemistry using antiserum to either synthetic PTHrP-(1-34) or recombinant PTHrP-(-5 to 139). Furthermore, these antisera were found to inhibit the ability of PTHrP-(1-34) to stimulate ROS cell cAMP production. When either antiserum (1:800-1:100 dilution) was added to subconfluent Hep G2 cells in medium containing 5% FBS for 3 days, a dose-related 40-50% increase in cell number occurred that could be inhibited by concurrent addition of 10 microM synthetic PTHrP-(1-36). The results show that Hep G2 cells synthesize and secrete both immunoreactive and biologically active PTHrP. As neutralization of PTHrP secreted by these cells by the addition of antiserum to PTHrP resulted in increased cell growth, the findings suggest that PTHrP can function as an autocrine or paracrine growth factor to suppress the growth of these human hepatoma cells.
Assuntos
Carcinoma Hepatocelular/patologia , Neoplasias Hepáticas/patologia , Proteínas/farmacologia , Animais , Sequência de Bases , Northern Blotting , Divisão Celular , Meios de Cultivo Condicionados , AMP Cíclico/biossíntese , Humanos , Dados de Sequência Molecular , Osteossarcoma/metabolismo , Proteína Relacionada ao Hormônio Paratireóideo , Reação em Cadeia da Polimerase , Proteínas/genética , Proteínas/metabolismo , RNA Mensageiro/análise , Ratos , Receptor Tipo 1 de Hormônio Paratireóideo , Receptores de Hormônios Paratireóideos/genética , Proteínas Recombinantes/farmacologia , Células Tumorais CultivadasRESUMO
Previously, using human hepatoma cells (HepG2), we found that immunoneutralization of secreted PTHrP increased cell growth. Here we asked whether PTHrP production was affected by agents that alter growth of Hep G2 cells. Immunoreactive PTHrP in medium and PTHrP mRNA expression were examined. Treatment of cells with 10 µM hydrocortisone or 1 ng/mL TGF-ß1 for 72 h inhibited cell growth by 28±6 and 36±2% and increased PTHrP in medium by 128±10 and 525 ±27%, respectively. The increase in PTHrP produced by both agents was dose-and time-dependent, and the increased PTHrP was accompanied by dose-and time-dependent enhanced expression of PTHrP mRNA. In contrast, 10% fetal bovine serum (FBS) for 72 h increased cell growth by 38±6% (vs serum-free medium) and decreased PTHrP production by 49±4% whereas culture in high glucose (3-4g/L) increased cell growth by 43±1% (vs 1 g/L glucose) and decreased PTHrP by 55±0.4%. Inhibition of PTHrP by both FBS and glucose was dose-dependent; FBS also inhibited PTHrP mRNA. The results show that increased cell growth was associated with decreased PTHrP production, while decreased growth was accompanied by increased PTHrP production. The findings imply that PTHrP may help mediate growth effects of these agents on Hep G2 cells.
RESUMO
BACKGROUND: This study was designed to determine whether the genes for both parathyroid hormone-related peptide (PTHrP) and its receptor were expressed in close proximity to one another in various regions of the gut and whether they both were evident in two intestinal epithelial cell lines. The findings would test the idea that PTHrP acts as an autocrine or paracrine factor in the gut. EXPERIMENTAL DESIGN: Reverse transcription/PCR and Northern analysis were used to detect mRNA for PTHrP and its receptor in various regions of the normal rat gut, in epithelial cell populations isolated along the villus tip-crypt axis in rat jejunum, and in a rat and a human gastrointestinal epithelial cell line (IEC-6 and LoVo, respectively). Antisera to PTHrP also were used to detect the peptide in rat gastrointestinal tissues or in growth medium from cultured cells. RESULTS: Both PTHrP and PTHrP receptor mRNA were found in all regions of the rat gut, in all cell populations isolated from rat jejunum, and in the rat and human cell lines. Immunoreactive PTHrP in tissue sections was observed in rat jejunal epithelial cells all along the villus but not in crypt cells, and immunoreactive peptide was found in growth medium from the cultured intestinal epithelial cells. CONCLUSIONS: The results show that genes for PTHrP and its receptor are expressed widely in gut epithelia. Expression of the two genes in the same regions of the gut and in the same cell line implies a local autocrine/paracrine action of the peptide. Expression of the peptide in villus epithelium but not in crypt cells suggests a role in differentiating gastrointestinal epithelial cells.
Assuntos
Mucosa Intestinal/metabolismo , Proteínas/genética , RNA Mensageiro/análise , Receptores de Hormônios Paratireóideos/genética , Animais , Sequência de Bases , Células Cultivadas , Epitélio/metabolismo , Imuno-Histoquímica , Dados de Sequência Molecular , Proteína Relacionada ao Hormônio Paratireóideo , Proteínas/análise , Proteínas/imunologia , Ratos , Ratos Sprague-Dawley , Receptor Tipo 1 de Hormônio ParatireóideoRESUMO
A C-terminal analog of parathyroid hormone-related peptide (PTHrP), PTHrP(107-139), was found to stimulate cAMP production in three osteoblast cell preparations. The effect was studied most extensively in ROS 17/2.8 cells. The effect was dose-related and comparable in magnitude to that produced by PTHrP(1-34), but potency was lower. The functional significance of the cAMP effect is unknown, but preliminary findings indicated that PTHrP(107-139) also inhibited osteopontin mRNA levels in ROS 17/2.8 cells treated with peptide for 48 h. The results suggest that the carboxy-terminal region of PTHrP may play a role in bone metabolism by influencing osteoblast activity.
Assuntos
AMP Cíclico/biossíntese , Osteoblastos/efeitos dos fármacos , Proteína Relacionada ao Hormônio Paratireóideo , Hormônio Paratireóideo , Fragmentos de Peptídeos/farmacologia , Proteínas/farmacologia , Animais , Osteoblastos/metabolismo , Ratos , Sistemas do Segundo Mensageiro/efeitos dos fármacos , Estimulação Química , Células Tumorais CultivadasRESUMO
Calcium, which binds to calmodulin inside the cells, is an important mediator of various intracellular processes, including cell proliferation. We speculated that blockade of Ca2+ influx into the cells by Ca(2+)-channel blockers, such as phenytoin and verapamil, might affect the Ca(2+)-calmodulin pathway leading to suppression of cell growth. In this study, we examined the effect of phenytoin and verapamil on growth of two human pancreatic cancer cell lines, MIA PaCa-2 and CAV, in vitro and in vivo. Both phenytoin and verapamil inhibited growth of the two cell lines in a dose-dependent fashion. Phenytoin and verapamil each significantly prolonged doubling time of MIA PaCa-2 and the combination of the two drugs acted synergistically. The activity of ornithine decarboxylase, which is a rate-limiting enzyme of the polyamine pathway that is closely related to cell proliferation, was significantly inhibited by both drugs in a time-dependent fashion. Phenytoin, but not verapamil, inhibited growth of MIA PaCa-2 tumors xenotransplanted into nude mice, whereas both phenytoin and verapamil inhibited the growth of CAV tumors. Since phenytoin and verapamil are known to have fewer side effects than conventional antineoplastic drugs, these results suggest their possible use in novel therapeutic strategies.
Assuntos
Bloqueadores dos Canais de Cálcio/uso terapêutico , Neoplasias Pancreáticas/tratamento farmacológico , Fenitoína/uso terapêutico , Verapamil/uso terapêutico , Divisão Celular/efeitos dos fármacos , Humanos , Neoplasias Pancreáticas/patologia , Células Tumorais CultivadasAssuntos
Infecções por HIV/prevenção & controle , Hepatite B/prevenção & controle , Doenças Profissionais/prevenção & controle , Austrália , Protocolos Clínicos , Desinfecção , Medicina de Família e Comunidade , Infecções por HIV/transmissão , Hepatite B/transmissão , Vacinas contra Hepatite B , Humanos , Ferimentos Penetrantes Produzidos por Agulha/prevenção & controle , Exposição Ocupacional , Roupa de Proteção , Eliminação de Resíduos , Esterilização , VacinaçãoRESUMO
Physiological roles for PTH-related peptide (PTHrP) appear varied, but remain to be clarified. The peptide is present in large amounts in milk, and PTHrP mRNA has been shown to be present in high amounts in lactating mammary gland. Because PTHrP can cause smooth muscle relaxation, we hypothesized that the peptide might affect the contractility of the breast myoepithelial cell and thereby affect milk ejection. To test this idea, we asked whether PTHrP might affect second messenger responses in a human mammary gland myoepithelial-cell line (Hs578Bst) derived originally from normal breast tissue. To verify the presumed origin of these cells, we also examined the effects of oxytocin. Cells were grown in culture in multiwell plates and exposed to test peptides for 15 min in buffer containing 1 mM isobutylmethylxanthine, and intracellular cAMP was measured by RIA. Both PTHrP-(1-34) and PTH-(1-34) increased cAMP in a dose-related fashion (ED50, 5 nM), with a maximal effect (3-fold) occurring at 100 nM. The ability of PTHrP to stimulate cAMP was inhibited by a 10- to 100-fold molar excess of the specific inhibitors, PTH-(3-34) or PTHrP-(7-34). Inhibitors alone did not alter cAMP. Oxytocin also produced an increase in cAMP, but the effect was inconsistent and occurred only with high doses (0.1-1 microM). Using cells grown on coverslips and loaded with fura-2AM, intracellular Ca2+ was monitored in cells exposed to test peptides. Oxytocin (0.2-20 nM) produced rapid dose-related increases in intracellular Ca2+, with a peak and plateau characteristic of initial mobilization of intracellular Ca2+, followed by entry of extracellular Ca. The plateau was eliminated by the Ca channel antagonist La3+ or by perfusion of cells with Ca-free medium. PTHrP (10-100 nM) altered the intracellular Ca2+ response to oxytocin in 66% of 39 preparations tested. PTHrP inhibited the Ca2+ response when given before oxytocin or transiently decreased the plateau phase of the Ca2+ response when given after oxytocin. Analysis of cellular mRNA using reverse transcription polymerase chain reaction indicated that these cells express the gene for PTHrP, and immunohistochemistry using antiserum to PTHrP revealed positive staining of cells. Measurement of immunoreactive PTHrP in conditioned medium confirmed that these cells can synthesize and secrete the peptide. The finding of a response of this cell line to oxytocin provides functional evidence of their myoepithelial derivation.(ABSTRACT TRUNCATED AT 400 WORDS)