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Biomedical subjects

R M Johnson

Publications and source records attributed to R M Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1993

High prevalence of Epstein-Barr virus in the Reed-Sternberg cells of Hodgkin's disease occurring in Peru.

The Epstein-Barr virus (EBV) has been implicated in the pathogenesis of Hodgkin's disease (HD). This study was undertaken to determine whether the association of EBV with HD showed geographical variation, as in Burkitt's lymphoma. We studied 32 formalin-fixed, paraffin-embedded cases of HD occurring in Peru. EBV DNA-RNA in situ hybridization was performed using a 30-base biotinylated antisense oligonucleotide complementary to the EBER1 gene of EBV. EBV immunohistochemistry was also performed, using a monoclonal antibody (MoAb) to the latent membrane protein (LMP1) of EBV. Identification of the precise cellular subset staining with EBV was accomplished via double-labeling with MoAbs directed against Reed-Sternberg cells (LeuM1/CD15) and B cells (L26/CD20). EBV RNA was identified in all or virtually all of the Reed-Sternberg cells and variants in 30 of the 32 (94%) cases of HD by in situ hybridization. LMP1 expression was identified in 83% of the EBER1-positive cases. Double-labeling studies confirmed the localization of EBV RNA to CD15-expressing Hodgkin's cells. This study found an extremely high prevalence of EBV in Peruvian HD, in contrast to the much lower percentage of EBV-associated cases of HD occurring in "Western" patients.

Adolescent↗
PubMed1993

Use of alprazolam for relief of tinnitus. A double-blind study.

OBJECTIVE: To systematically test the effectiveness of alprazolam as a pharmacological agent for patients with tinnitus. DESIGN: Prospective, placebo-controlled, double-blind study. PATIENTS: Forty adult patients with constant tinnitus who had experienced their tinnitus for a minimum of 1 year and who resided in the Portland, Ore, metropolitan area. Twenty patients were randomly assigned to the experimental group and 20 to the control group. RESULTS: Seventeen of 20 patients in the experimental (alprazolam) group and 19 of the 20 in the placebo (lactose) group completed the study. Of the 17 patients receiving alprazolam, 13 (76%) had a reduction in the loudness of their tinnitus when measurements were made using a tinnitus synthesizer and a visual analog scale. Only one of the 19 who received the placebo showed any improvement in the loudness of their tinnitus. No changes were observed in the audiometric data or in tinnitus masking levels for either group. Individuals differed in the dosages required to achieve benefit from the alprazolam, and the side effects were minimal for this 12-week study. CONCLUSIONS: Alprazolam is a drug that will provide therapeutic relief for some patients with tinnitus. Regulation of the prescribed dosage of alprazolam is important since individuals differ considerably in sensitivity to this medication.

Adult↗
PubMed1993

Effects of high extracellular calcium and strontium on inositol polyphosphates in bovine parathyroid cells.

The addition of Ca2+ or a variety of divalent cations increases intracellular Ca2+ in parathyroid cells and suppresses secretion. Since 1,4,5-inositol trisphosphate (IP3) and 1,3,4,5-inositol tetrakisphosphate (IP4) mediate Ca2+ mobilization in other systems, we examined high Ca(2+)- and Sr(2+)-induced accumulation of IP3 and IP4 isomers by anion-exchange HPLC and measured 1,4,5-IP3 mass in parathyroid cells. Raising extracellular [Ca2+] from 0.5 to 3.0 mM increased 3H-1,4,5-IP3 within 5 s, which was confirmed by mass measurements. 3H-1,3,4-IP3 rose gradually by 10 s and increased for 60 s after the addition of Ca2+. Although we detected no change in 3H-1,3,4,5-IP4, the increase in 3H-1,3,4-IP3 suggests that 3H-1,3,4,5-IP4 was being formed. The addition of 4 mM SrCl2 produced similar changes in 1,4,5-IP3, which were confirmed by mass assay. 3H-1,3,4,5-IP4 did not change. However, Sr2+ induced a gradual increase in 3H-1,3,4-IP3, which remained above control levels for 5 minutes. Isotopic labeling studies in this system may underestimate changes in 1,4,5-IP3 mass, but both mass and radioisotopic analyses indicate that high extracellular Ca2+ and Sr2+ stimulate substantial increases in 1,4,5-IP3 without significant accumulation of 1,3,4,5-IP4. These studies suggest a role for 1,4,5-IP3 in intracellular Ca2+ mobilization by divalent cations in parathyroid cells.

Animals↗
PubMed1993

5-HT3 receptor ligands lack modulatory influence on acetylcholine release in rat entorhinal cortex.

The objective of this study was to explore the role of 5-HT3 receptors in modulating potassium (K+)-evoked release of [3H]-acetylcholine ([3H]-ACh) from superfused slices of rat entorhinal cortex previously loaded with [3H]-choline. Rat entorhinal cortices were cross-chopped into 300 microns slices, superfused with oxygenated Krebs buffer containing 2.5 mmol/l Ca2+ and stimulated with two consecutive exposures of 20 mmol/l K+ for 4 min (S1 and S2, respectively). Compounds were added 20 min before S2 stimulation and remained in the superfusion buffer for the duration of the experiment. The S2/S1 ratio was then calculated. Stimulated release of [3H]-ACh was dependent on extracellular Ca2+ and K+ concentration. In Sprague Dawley rats, 2-methyl-5-HT (10(-9)-10(-6) mol/l), in the presence of 1 mumol/l ritanserin or 1 mumol/l ondansetron, had no influence on K(+)-evoked release of [3H]-ACh. In slices prepared from Hooded Lister rats, 2 mumol/l 5-HT but not 2-Me-5-HT significantly (P < 0.05) inhibited K(+)-evoked [3H]-ACh release only 17% in the presence of 1 mumol/l ritanserin. However, 2 mumol/l 2-Me-5-HT plus 1 nmol/l ondansetron had no effect. High performance liquid chromatography coupled to electrochemical detection (HPLC-ECD) was used to monitor endogenous release of ACh in the above conditions to confirm data from the radiolabelled experiments. No significant inhibition or increase in K(+)-evoked ACh release was observed with either 5-HT3 receptor agonists or antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

High-grade transformation of chronic lymphocytic leukemia and low-grade non-Hodgkin's lymphoma. Genotypic confirmation of clonal identity.

The abrupt appearance of a high-grade tumor in patients with low-grade malignant lymphoma usually is associated with an accelerated clinical disease course. The high-grade lymphoma may take a variety of histologic forms and often, but not always, represents evolution of the original low-grade disease, as shown by immunophenotypic or immunogenotypic studies. The authors describe the transformation of a variety of low-grade B-cell neoplasms to high-grade tumors in four patients. The initial diagnoses included chronic lymphocytic leukemia and mantle cell lymphoma in one patient each and low-grade follicular lymphoma in two patients. The high-grade tumors were classified as lymphoblastic lymphoma in one patient and small noncleaved cell lymphoma in two patients. The high-grade component manifests primarily in the peripheral blood as circulating blast-like cells consistent with large-cell lymphoma in the remaining patient. In each case, immunophenotypic studies showed identical monoclonal surface immunoglobulin expression on the low- and high-grade tumors. Immunoglobulin heavy chain gene and kappa light chain gene studies showed identical clonally rearranged bands in paired samples from three of the four patients, a finding indicative of clonal identity. Unexpectedly, dissimilar immunoglobulin light and heavy chain gene rearrangements were detected in the paired samples from one patient with previously diagnosed follicular lymphoma, making the relationship of the two tumors from this patient uncertain; however, additional Southern blot analysis of the bcl-2 gene showed identical rearrangements in both lesions. Furthermore, polymerase chain reaction across the t(14;18) major breakpoint region in both tumors amplified nucleotide fragments of identical size, confirming the clonal identity of the low- and high-grade lymphomas despite the divergent immunoglobulin gene studies. These studies show that low-grade malignant lymphomas of small lymphocytic, mantle cell, or follicular small cleaved cell types may assume high-grade morphologic characteristics, that this change is the result of transformation of the preexisting low-grade malignant neoplasm, and that this progression, like typical Richter's syndrome, is associated with a dramatically accelerated clinical course. In addition, these studies confirm previous reports that disparate immunoglobulin light and heavy chain gene rearrangements are not necessarily an indicator of different cellular origins, and additional genotypic studies occasionally may be required to show the clonal identity of the cell population involved in these morphologic transformations.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Rearrangement of the BCL-2 gene in follicular lymphoma. Detection by PCR in both fresh and fixed tissue samples.

Rearrangement of the BCL-2 gene is the molecular consequence of the t(14;18) chromosomal translocation, which is found in approximately 60-90% of follicular lymphomas. To investigate the ability of the polymerase chain reaction (PCR) to detect this rearrangement in fixed-tissue samples, we studied 48 cases of follicular lymphoma using DNA extracted from paired samples of fresh-frozen tissue and formalin-fixed, paraffin-embedded tissue. A standard phenol-chloroform DNA extraction method was used for both types of tissue. Rearrangements of the major breakpoint region (MBR) and minor cluster sequence (MCS) were examined. Three segments of the human beta-globin gene were also amplified to estimate the degree of DNA degradation in the fixed-tissue samples. PCR of fresh-tissue (intact) DNA revealed amplifiable products in 29 of the 48 follicular lymphomas (60%), whereas the fixed-tissue (degraded) DNA studies were positive in 24 (50%). MBR products were detected in 24 fresh-tissue samples, and varied from 80 bp to > 1.5 kb. Twenty of these cases yielded MBR products in the corresponding fixed-tissue DNA, ranging from 80 to 276 bp. Five fresh-tissue and four fixed-tissue samples produced MCS segments that ranged from 340 bp to 1.2 kb. Four of the five samples with no detectable MBR or MCS translocations using degraded DNA had products greater than 1.0 kb in the fresh-tissue studies. A 175-bp segment of the beta-globin gene was amplified in all 29 fixed-tissue samples; a 324 bp fragment was produced in 20 samples (69%), and a 676 bp segment was detected in 13 (45%).(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

The bone marrow agar section: a morphologic and immunohistochemical evaluation.

A technique for agar embedding of bone marrow aspirate particles is compared with the conventional aspirate smear and bone marrow biopsy by reviewing 503 consecutive bone marrow specimens. Immunohistochemical studies were performed on both agar sections and bone marrow biopsies on 43 paired specimens to compare the results between the two preparations. The results were also compared with traditional clot sections from ten control cases. Of the 382 cases with agar sections, 97.7% contained material in the agar that was diagnostic alone or supportive of the diagnosis made with the biopsy and aspirate smear. In two cases (0.4%), focal involvement by lymphoma was identified on the agar section but not in the biopsy sections or aspirate smears. The immunohistochemical studies showed superior immunoreactivity in agar sections by lymphoproliferative disorders when compared with bone marrow biopsy sections. Similar results between agar and conventional biopsy sections were found in cases of metastatic carcinoma and plasma cell dyscrasias.

Adolescent↗
PubMed1993

Modified celluloses for erythrocyte deformability fractionation.

Cellulose columns have been used to separate erythrocytes into deformability classes, but recoveries have been variable and incomplete. Columns of modified cellulose (propylaminocarbonylmethyl cellulose [PAC] and butylisourea cellulose [BIC]) were effective in increasing the recovery of both normal and sickle cells applied to the columns, with reasonable yields of rigid cells in the late fractions. In particular, sickle cells were recovered in 95% yield, and late eluting cells had a sharply reduced deformability index.

Anemia, Sickle Cell↗
PubMed1993

Brain lymphomas of immunocompetent and immunocompromised patients: study of the association with Epstein-Barr virus.

The Epstein-Barr virus (EBV) has been described in association with lymphomas of the central nervous system. To test if the association between EBV and central nervous system lymphomas was limited to patients with immunosuppression or whether the association also held for patients who were immunocompetent and to determine the true prevalence of any association, we studied 37 formalin-fixed, paraffin-embedded cases of central nervous system lymphomas occurring in immunocompromised and immunocompetent patients. EBV DNA-RNA in situ hybridization was performed using a 30-base biotinylated antisense oligonucleotide complementary to the EBER1 gene of EBV. Immunohistochemistry was also performed, using a monoclonal antibody to the latent membrane protein of EBV. The most common histologic subtypes of lymphoma were high grade immunoblastic (57%), diffuse large cell (22%), and small, noncleaved, non-Burkitt's (11%). Eighty-six percent of all tumors in our series were of B-cell lineage, as confirmed by CD20 expression, but only 37% of the primary tumors showed restricted CD20 expression. EBV RNA was identified in all or virtually all of the malignant lymphoid cells in 11 of the 37 cases (30%), including 10 primary brain lymphomas and one metastasis from systemic disease. Latent membrane protein expression was identified in 64% of the EBER1-positive cases. All 10 patients who had a history of immunosuppression had tumors that expressed EBV RNA. We confirm the strong association of EBV with brain lymphomas occurring in immunocompromised patients, whether due to AIDS or to the immunosuppression associated with organ transplantation. Our findings also demonstrate a low rate of EBV-positivity in immunocompetent patients.

Adolescent↗
PubMed1992

Induction of a Ca(2+)-activated K+ channel in human erythrocytes by mechanical stress.

Mechanical deformation of normal ATP-replete human erythrocytes increased their permeability to Ca2+ sufficiently to turn on the Ca(2+)-activated K+ channel (the Gardos channel). When Ca2+ is absent, mechanical deformation of normal erythrocytes induces an equivalent increase the permeability of both Na+ and K+, In the presence of 0.1 to 1 mM Ca2+, a further increase in the K+ efflux rate was seen. There was no increase in Na+ flux above that induced by deformation itself. The involvement of the Ca(2+)-activated H channel was verified by showing the specific inhibitors of the channel, quinine and charybdotoxin, prevent the Ca(2+)-induced increase in K+ efflux. These results are consistent with a model of sickle cell dehydration proposed by Bookchin et al. ((1987) Prog. Clin. Biol. Res. 240, 193-200). The estimated rate of Ca2+ entry under these conditions (37 degrees C, 1000 dyne/cm2, and laminar shear) was about 1 mmol/loc per h.

Adenosine Triphosphate↗
PubMed1992

A murine CD4-, CD8- T cell receptor-gamma delta T lymphocyte clone specific for herpes simplex virus glycoprotein I.

The role of TCR-gamma delta T lymphocytes in immune responses is currently not well understood. TCR-gamma delta cells have a limited repertoire suggesting that TCR-gamma delta T a limited number of evolutionarily conserved Ag such as nonpolymorphic MHC and heat shock proteins. TCR-gamma delta T lymphocytes appear in enhanced numbers in skin lesions produced by Mycobacterium leprae and in the synovial fluid of joints affected by rheumatoid arthritis, raising the possibility that this subset of T lymphocytes may play a role in control of infectious processes and in autoimmune diseases. We report the identification of a TCR-gamma delta T cell clone isolated from a HSV-infected mouse that recognizes glycoprotein I of HSV type 1. Clone recognition of glycoprotein I does not appear to require the expression of MHC class I or class II gene products. These data suggest that TCR-gamma delta lymphocytes may play an important role in the immune response to viral infections.

Animals↗
PubMed1992

Estrogen-dependent, tamoxifen-resistant tumorigenic growth of MCF-7 cells transfected with HER2/neu.

Since the poor prognosis associated with HER2 amplified breast cancers might be explained by a mechanistic association between p185HER2 overexpression and therapeutic resistance, we assessed the chemo-endocrine sensitivity of estrogen receptor (ER) containing MCF-7 breast cancer cells transfected with full-length HER2 cDNA. Of the 36 isolated MCF/HER2 subclones, 7 were found to overexpress p185HER2 surface receptor at levels 3 to 45-fold greater than parental or control transfected cells (MCF/neo). The overexpressing transfectants possessed increased inositol-1,4,5-triphosphate-3'-kinase activity comparable to enzyme activity in the endogenously HER2 amplified breast cancer cell lines SK-Br-3 and BT-474. The anti-p185HER2 monoclonal antibody and receptor-specific partial agonist, muMAb4D5 (4D5), known to inhibit growth of SK-Br-3 and BT-474 cells, produced no significant growth inhibitory effect on any of the transfectants including the 45-fold overexpressing MCF/HER2-18 cells which were studied in greater detail. MCF/HER2-18 cells contained at least partially functioning exogenous receptor since 4D5 (3 micrograms/ml) specifically stimulated phosphorylation of p185HER2 and its co-precipitating ptyr56 substrate within 5 min, and this was followed at 1 h by a transient induction of c-myc but not c-fos mRNA. ER content and the in vitro sensitivity of MCF/HER2-18 cells to 5-fluorouracil and adriamycin were identical to those of control transfectants and parental cells. However, these highly overexpressing transfectants had acquired low level (2 to 4-fold) resistance to cisplatin and were no longer sensitive to the antiestrogen tamoxifen (TAM). To compare the hormone-dependent tumorigenicity of the HER2 transfectants, MCF/HER2-18 and control cells (MCF, MCF/neo-3) were implanted into ovariectomized athymic nude mice. No tumors were produced in the absence of estradiol (E2) administration. In E2 supplemented mice, MCF/HER2-18 tumors grew most rapidly. When E2 treatment was stopped and daily TAM injections were initiated, MCF-7 and MCF/neo-3 tumor growth ceased immediately, while MCF/HER2-18 tumors continued to show an accelerated growth rate lasting weeks. This pattern of hormone-dependent, TAM-resistant growth exhibited by the MCF/HER2-18 tumors in nude mice supports the possibility that p185HER2 overexpression in human breast cancers may be linked to therapeutic resistance.

Adenocarcinoma↗
PubMed1992

A large erythroid spectrin beta-chain variant.

A large variant of erythrocyte beta-spectrin was found in a child presenting with hereditary elliptocytosis and anaemia. This polypeptide was phosphorylated, cross-reacted with normal beta-spectrin in immunoblotting and formed a dimer with alpha-spectrin that co-purified with normal alpha beta dimer. The molecular weight was estimated to be 330 kD by SDS gel electrophoresis, which is 84 kD (35%) larger than the normal beta-chain. This variant has been tentatively named spectrin Detroit (beta Detroit). Tryptic digests demonstrated a coexisting alpha-spectrin variant Sp alpha I/65 in the propositus, his father and a paternal uncle. Anaemia and elliptocytosis was associated with Sp alpha I/65 rather than beta Detroit, since other family members with beta Detroit in whom alpha-spectrin was normal had no morphological or clinical abnormalities. Family members were identified who had normal alpha-spectrin but were heterozygotic for the large beta-spectrin. Their erythrocyte membranes were more rigid and fragile than normal. The fragility is probably a consequence of both weaker dimer association and spectrin deficiency. Variant spectrin dimers (alpha beta Detroit) had a reduced self-association constants. Binding to ankyrin was normal. Instability of beta Detroit during erythropoiesis is suggested by the fact that it comprises only 25% of the beta-spectrin in beta Detroit heterozygote erythrocytes, and total spectrin was reduced by 20%. Although beta Detroit has some functional defects, this 84 kDa insert in erythrocyte spectrin is compatible with nearly normal function.

Centrifugation, Density Gradient↗
PubMed1992

Comparison of second messenger formation in human keratinocytes following stimulation with epidermal growth factor and bradykinin.

We have examined the ability of recombinant human epidermal growth factor (EGF) and bradykinin (BK) to stimulate formation of inositol polyphosphates and sn-1,2-diacylglycerol (DAG), and mobilize intracellular Ca2+ ([Ca2+]i) in adult human keratinocytes (KC). Inositol polyphosphates were resolved by high performance liquid chromatography coupled with flow detector spectroscopy. Free intracellular calcium was quantitated using digital ratio imaging fluorescence microscopy of fura-2 loaded KC. The mass amount of DAG was quantitated using the DAG kinase reaction. When comparing maximal doses of BK (0.1 microM) and EGF (200 ng/ml), BK stimulated larger increases in all second messengers measured. The majority of cells responded rapidly to BK with global increases in [Ca2+]i. Cells responding to EGF were fewer in number and slower to respond with the Ca2+ signal being less pronounced. Treatment of cells with pertussis toxin (PTX) for 24 h significantly attenuated the BK-stimulated inositol polyphosphate formation and [Ca2+]i while the EGF response remained unaffected in both parameters. BK (10(-9) to 10(-6) M) did not stimulate DNA synthesis in KC as measured by [3H]-thymidine incorporation when cultures were treated for 5 days. These results demonstrate that the coupling and biochemical signals produced by stimulation of BK and EGF receptors in human KC are different and suggests that stimulation of second messenger formation from inositol lipid hydrolysis may not be an absolute requirement for the initiation of cell proliferation.

Bradykinin↗
PubMed1991

Purification of band 7.2b, a 31-kDa integral phosphoprotein absent in hereditary stomatocytosis.

A 31-kDa human erythrocyte integral protein, band 7.2b, has been purified to better than 95% homogeneity. The polypeptide was found to be insoluble in most detergents and was isolated in denatured form by gel filtration in the presence of sodium dodecyl sulfate and preparative electrophoresis. In intact erythrocytes that were equilibrated with 32Pi, band 7.2b was phosphorylated in response to exogenous dibutyryl cAMP. The peptide is also palmitylated, as shown by its incorporation of radioactivity when intact erythrocytes were incubated with [9,10-3H]palmitic acid. Antisera to band 7.2b were raised in rabbits, and these antibodies cross-react with 31-kDa polypeptides in human liver and kidney. Immunoblots of red cells from a number of other species were negative, with the exception of a cross-reacting 23-kDa polypeptide in rat erythrocyte membranes. Band 7.2b was absent in erythrocyte membranes from an individual with overhydrated hereditary stomatocytes.

Amino Acids↗
PubMed1991

p185HER2 signal transduction in breast cancer cells.

A partially agonistic monoclonal antibody, 4D5, known to bind to the extracellular domain of p185HER2 and shown to inhibit long term growth of p185HER2-overexpressing breast cancer cells, was used to study signal transduction and phosphotyrosyl protein substrates associated with this receptor. Normal breast epithelial cells and breast carcinoma cells expressing low levels of p185HER2 were not affected by 4D5. HER2/neu-overexpressing breast cancer cells (BT-474 and SK-Br-3) exposed to 4D5 exhibited rapid phosphorylation of both p185HER2 and an associated 56-kDa phosphotyrosyl protein (ptyr56). Paralleling the 4D5- stimulated phosphorylation of p185HER2 and ptyr56 was a 5-10-fold induction of c-fos mRNA and phosphatidylinositol 4-kinase activity and a 2-fold induction of inositol 1,4,5-trisphosphate 3'-kinase activity. The increased phosphatidylinositol 4-kinase activity immunoprecipitated with p185HER2 and also co-eluted with ptyr56 from an antiphosphotyrosine immunoaffinity column. These results indicate that short term (less than 6 h) 4D5 activation of p185HER2 in overexpressing breast cancer cells produces agonistic-like signaling typical of homologous tyrosine kinase growth factor receptors such as epidermal growth factor receptor. The data also suggest that ptyr56 represents a novel phosphorylated substrate associated with 4D5-stimulated p185HER2.

Blotting, Western↗
PubMed1991

Thrombin and parathyroid hormone mobilize intracellular calcium in rat osteosarcoma cells by distinct pathways.

The mechanisms by which PTH and thrombin mobilize intracellular Ca2+ (Cai2+) were examined in UMR 106-H5 rat osteosarcoma cells. Bovine PTH-(1-34) (24 pM to 240 nM) produced a dose-dependent increase in Cai2+ (EC50, 3 nM), which returned to baseline within 75 sec. Human alpha-thrombin produced an increase in Cai2+ (ECmax, 10 U/ml) which was similar to that of PTH with respect to both magnitude and time course. Chelation of extracellular calcium with 5.0 mM EGTA did not alter the Cai2+ response to either PTH or thrombin. When added together at maximally effective concentrations, PTH and thrombin produced additive effects on Cai2+ in the presence and absence of EGTA. The additive effects of PTH and thrombin on Cai2+ were confirmed at the single cell level, using laser-based image analysis. Bradykinin (1 microM) produced a significant increase in Cai2+ in UMR 106-H5 cells which was of lesser magnitude than the peak 2- to 3-fold increase elicited by PTH or thrombin. Preexposure of cells to 10 U/ml thrombin for 2 min abolished the Cai2+ response to bradykinin, whereas preexposure to 240 nM PTH had no effect on the Cai2+ response to bradykinin. Thrombin elicited a rapid increase in the accumulation of 3H-labeled inositol phosphates (IP2 and IP3) in UMR 106-H5 cells, with increases in [3H]1,4,5-IP3 detectable as early as 15 sec after the addition of thrombin. Bradykinin increased [3H]IP production to a lesser extent than thrombin, whereas PTH neither increased [3H]IP accumulation nor potentiated the [3H]IP response to thrombin. The results suggest that thrombin and bradykinin mobilize Cai2+ from a shared IP3-responsive calcium pool, whereas PTH may use signals in addition to 1,4,5-IP3 to mobilize calcium from a distinct cellular calcium pool. Alternatively, specific calcium compartmentalization exists, and there is differential coupling of these agonists to the 1,4,5-IP3/Cai2+ pathway.

Animals↗