The epidemiology of shoulder dislocations in Oslo.

There are few previous studies on the incidence of shoulder dislocation in the general population. The aim of the study was to report the incidence of acute shoulder dislocations in the capital of Norway (Oslo) in 2009. Patients of all ages living in Oslo, sustaining a dislocation of the glenohumeral joint, were identified using electronic diagnosis registers, patient protocols, radiological registers of the hospitals, and the Norwegian Patient Register (NPR). The overall incidence rate was 56.3 [95% confidence interval (CI) 50.2-62.4] per 100,000 person-years, with rates of 82.2 (95% CI 71.7-92.8) and 30.9 (95% CI 24.5-37.3) in men and women, respectively. The incidence of primary dislocations was 26.2 (95% CI 22.1-30.4). The overall incidence of shoulder dislocations in Oslo was higher than previously reported incidences. The incidence of primary dislocations was also higher than that in previously reported studies for the general population but it was close to the incidence reported in Malmø, Sweden.

Capsular lesions with glenohumeral ligament injuries in patients with primary shoulder dislocation: magnetic resonance imaging and magnetic resonance arthrography evaluation.

The glenohumeral ligaments are important structures for the stability of the shoulder. They are integrated parts of the capsule and are at risk to be injured in a traumatic shoulder dislocation. The aim was to examine the prevalence of capsular ligament lesions in the acute phase and at minimum 3 weeks' follow-up after first-time traumatic shoulder dislocation. Forty-two patients aged 16-40 years were included. All patients underwent computed tomography and magnetic resonance imaging (MRI) scans shortly after the injury and MR-arthrography (MRA) at follow-up. The median time from dislocation to MRI was 7 (range 2-14) days and to MRA 30 (range 21-54) days. We found capsular ligament lesions in 22 patients (52.4%) in the acute stage and in five patients (11.9%) at follow up. Nine patients (21.4%) had a humeral avulsion of the anterior glenohumeral ligament (HAGL lesion) on MRI. Three patients (7.1%) had this lesion at follow-up. The rate of HAGL lesions in the acute stage was higher than reported previously, but the prevalence at follow-up was in keeping with earlier published studies.

Angiotensin II activates a bumetanide sensitive increase in 86RB+ efflux in the rat heart.

We previously reported that alpha-adrenoceptor (AR) stimulation of the isolated perfused rat heart increased the efflux of 42K+ and the K+ analogue 86Rb+. The main part of this increase was bumetanide sensitive, indicating an activation of the Na+/K+/2Cl- cotransporter. The purpose of the present study was to investigate the effects of angiotensin II (1-100 nmol/l) and the protein kinase C (PKC) activator PMA (phorbol-12-myristate-13-acetate, 1-1000 nmol/l) on 86Rb+ efflux from isolated rat hearts and to compare the effects with the effect of the alpha1- AR agonist phenylephrine (30 micromol/l) in the presence of a beta-AR antagonist. Phenylephrine increased the 86Rb+ efflux rate by 47+/-4.1% (n=5, p<0.001). Angiotensin II induced a maximal increase in 86Rb+ efflux rate of 13+/-1.6% (n=12, p<0.0001). The effect of angiotensin II was totally eliminated by bumetanide (50 micromol/l). PMA decreased the 86Rb+ efflux rate by 23+/-7.0 % (n=7, p=0.02) and this effect of PMA was not sensitive to bumetanide. Pre-treatment of the hearts with PMA for 30 min did not influence the response to phenylephrine. In conclusion, angiotensin II stimulation, but not PKC activation by PMA increased the 86Rb+ efflux rate in isolated rat hearts, but the effect was smaller than that of alpha1- AR stimulation. The effect of angiotensin II was completely abolished by bumetanide indicating an activation of the Na+/K+/2Cl- -cotransporter.

Alpha1-adrenergic activation of myocardial Na-K-2Cl cotransport involving mitogen-activated protein kinase.

The translocation mechanisms involved in the alpha1-adrenoceptor-stimulated efflux of the potassium analog 86Rb+ were studied in isolated rat hearts. Phenylephrine (in the presence of a beta-blocker) increased the efflux of 86Rb+ and 42K+, and the Na-K-2Cl (or K-Cl) cotransport inhibitor bumetanide reduced the response by 42 +/- 11%. Furosemide inhibited the response with a lower potency than that of bumetanide. The bumetanide-insensitive efflux was largely sensitive to the K+ channel inhibitor 4-aminopyridine. Inhibitors of the Na+/H+ exchanger or the Na+-K+ pump had no effect on the increased 86Rb+ efflux. The activation of the Na-K-2Cl cotransporter was dependent on the extracellular signal-regulated kinase (ERK) subgroup of the mitogen-activated protein (MAP) kinase family. Phenylephrine stimulation increased ERK activity 3.4-fold. PD-98059, an inhibitor of the ERK cascade, reduced both the increased 86Rb+ efflux and ERK activity. Specific inhibitors of protein kinase C and Ca2+/calmodulin-dependent kinase II had no effect. In conclusion, alpha1-adrenoceptor stimulation increases 86Rb+ efflux from the rat heart via K+ channels and a Na-K-2Cl cotransporter. Activation of the Na-K-2Cl cotransporter is apparently dependent on the MAP kinase pathway.

Receptor subtypes involved in the alpha1-adrenoceptor mediated increase in 86Rb+ efflux from the rat heart.

The aim of this study was to determine the involvement of the different alpha1-adrenoceptor subtypes in the alpha1-adrenoceptor mediated increase in 86Rb+ efflux from rat hearts. Isolated hearts were perfused in the presence of a beta-adrenoceptor antagonist (1 microM timolol). After loading with 86Rb+, the efflux was measured during alpha1-adrenoceptor stimulation by phenylephrine (30 microM). Phenylephrine increased the 86Rb+ efflux by about 30%. Pretreatment with the preferentially alpha1B-adrenoceptor inhibitor chloroethylclonidine (CEC), reduced the response to phenylephrine by about 50%. The preferential alpha1D-adrenoceptor inhibitor BMY 7378 inhibited the response to phenylephrine by 35%, with a pKI=8.4 (95% C.I. 8.2-8.6). The response was sensitive to the preferential alpha1A-adrenoceptor inhibitors (+)niguldipine, 5-methylurapidil (5-MU) and WB-4101 at relatively high concentrations, and 5-MU inhibited the response with a pKI=7.7 (95% C.I. 7.2-8.0) in CEC pretreated hearts. In conclusion, the phenylephrine stimulated increase in 86Rb+ efflux in the rat heart is not specifically linked to only one of the alpha1-adrenoceptor subtypes, but involves the alpha1B- and the alpha1D-adrenoceptor subtypes, and probably the alpha1A-adrenoceptor subtype as well.

Alpha 1-adrenoceptor mediated activation of Na/K/2Cl cotransport and K+ channels in the rat heart involves different receptor subtypes.

Involvement of receptor subtypes in the alpha 1-adrenoceptor mediated activation of Na/K/2Cl-cotransport and K+ channels was studied in isolated perfused spontaneously beating rat hearts stimulated by phenylephrine (30 mumol/l) in the presence of a beta-adrenoceptor antagonist (1 mumol/l timolol). The effects of alpha 1-adrenoceptor stimulation on K+ translocation mechanisms were studied by measuring the efflux of 86Rb+ (a potassium analogue). The effects of 50 mumol/l bumetanide (Na/K/2Cl-cotransport inhibitor) and 0.1-0.3 mmol/l 4-aminopyridine (inhibitor of K+ channels) were studied in the presence of alpha 1-adrenoceptor subtype selective antagonists. Bumetanide reduced the alpha 1-adrenoceptor mediated increase in 86Rb+ efflux by 53 +/- 16.4% (n = 14, P < 0.001) in hearts pretreated with the preferentially alpha 1B-adrenoceptor antagonist chloroethylclonidine (CEC, 10 mumol/l), and by 35 +/- 7.3% (n = 15, P < 0.001) in the presence of the preferentially alpha 1D-adrenoceptor antagonist BMY 7378 (1 mumol/l). In the presence of the preferentially alpha 1A-adrenoceptor antagonist 5-methylurapidil (10 mumol/l), however, bumetanide had no effect on the response to phenylephrine. 4-Aminopyridine reduced the phenylephrine stimulated 86Rb+ efflux in the presence of 5-methylurapidil, but the effect of the K(+)-channel blocker was eliminated in CEC treated hearts. Thus the effects of the two translocation inhibitors were influenced differently by the two subtype selective antagonists, showing that alpha 1-adrenoceptor stimulation activates a bumetanide sensitive Na/K/2Cl-cotransport mechanism in the rat heart mainly through the alpha 1A-receptor subtype while the 4-aminopyridine sensitive K+ channels, are mainly activated by the alpha 1B-adrenoceptor subtype.

Concentration-response relationship of alpha 1-adrenoceptor-stimulated increase of 86Rb+ efflux in rat heart.

UNLABELLED: The aim of the present study was to establish a concentration-response relationship for the alpha 1-adrenoceptor mediated increase of 86Rb+ efflux, and to characterize the sensitivity of this response to the selective alpha 1-adrenoceptor antagonist prazosin. Isolated rat hearts were perfused retrogradely at constant flow and at 31 degrees. Timolol (10(-6) mol/l) was used to block beta-adrenoceptors. After a loading period with 86Rb+ and 55 min. washout, the hearts were exposed to phenylephrine in a concentration range from 3 x 10(-8) mol/l to 10(-4) mol/l. Control experiments comparing the effects of alpha 1-adrenoceptor stimulation on 86Rb+ efflux and 42K+ efflux were performed. alpha 1-Adrenoceptor stimulation increased the 86Rb+ efflux with a pD2 = 6.35 +/- 0.20 (mean +/- S.E.M). The maximal response to phenylephrine was 22.5 +/- 2.0% (mean +/- S.E.M.) of the control values. The concentration-response curve was shifted to higher concentration of agonist in the presence of the alpha 1-adrenoceptor antagonist prazosin (3 x 10(10) mol/l). The calculated inhibition constant for prazosin was 6.1 x 10(-11) mol/l. 86Rb+ was found to be a suitable K+ analogue in the study of relative changes in K+ efflux although the basal efflux kinetics were different for the two isotopes. CONCLUSION: Phenylephrine increased the 86+b+ efflux concentration-dependently. A high sensitivity to prazosin confirmed the involvement of the alpha 1-adrenoceptor population.

Inositol-1,4,5-trisphosphate mass content in isolated perfused rat heart during alpha-1-adrenoceptor stimulation.

Inositol-1,4,5-trisphosphate (IP3) has been proposed to be a second messenger in response to alpha-1-adrenoceptor stimulation also in myocardial cells. We studied the effect of alpha-1-adrenoceptor stimulation (5 x 10(-5) mol/l phenylephrine or 5 x 10(-5) mol/l noradrenaline both in the presence of 10(-6) mol/l timolol) on IP3 mass content in isolated perfused rat hearts. IP3 content was determined by a specific receptor-binding assay-kit (TRK 1000, Amersham) after validating the method. For comparison also the effect of muscarinic stimulation (10(-4) mol/l carbachol in the presence of 10(-6) mol/l timolol) on IP3 content was measured in corresponding preparations. A basal IP3 level of about 75 pmol/mg protein was found. There were no prominent effects of alpha-1-adrenoceptor stimulation on total IP3 content in isolated perfused rat hearts. Phenylephrine gave a statistically significant increase of about 40% at 1/4 min and a statistically significant decrease of about 25% at 4 min after start of exposure. Noradrenaline, however, gave no statistically significant change of IP3 at the time-points studied. Muscarinic stimulation caused a slight, statistically insignificant, increase of IP3 at 1/4 min. The results are compatible with an assumption that agonist stimulation evokes a localized increase of IP3 which may be masked by a relatively high total IP3 mass content. The IP3 peak after phenylephrine coincided with the early positive inotropic phase of the response reported earlier in perfused rat hearts for alpha-1-adrenoceptor stimulation by phenylephrine. Although this might be compatible with a role for IP3 in this early and transient phase, a mediator function of IP3 in the inotropic response is not established.

Increased intracellular potassium and water contents in rat heart after alpha-1-adrenoceptor stimulation.

Potassium accumulation in rat heart after alpha-1-adrenoceptor stimulation has previously been reported from indirect measurements. Here we present data on intracellular potassium content measured directly in the heart. Isolated rat hearts perfused in a non-recirculating system were exposed to alpha-1-adrenoceptor stimulation (5 x 10(-5) mol/l phenylephrine in the presence of 10(-6) mol/l timolol). 14C-Sucrose was used to estimate the extracellular space. From heart homogenates intracellular potassium, magnesium and cellular water contents were determined and the ion concentrations calculated accordingly. The intracellular magnesium content remained unchanged during all experimental conditions. alpha-1-Adrenoceptor stimulation evoked an increase in potassium content by 9% (4, 14; 95% confidence interval (CI), P = 0.0006). Due to an observed increase in intracellular water by 17% (9, 26; 95% CI, P = 0.0006), the potassium concentration apparently decreased by 8% (0.3, 15; 95% CI, P = 0.04). During partial inhibition of the Na+/K(+)-ATPase by 10(-5) mol/l ouabain, there was an increase in potassium content by 5% (1, 9; 95% CI, P = 0.008). There was, however, no significant increase in intracellular water in this situation. Calculated intracellular potassium concentration showed accordingly a slight increase. The effects upon potassium and water both in the absence and presence of ouabain were eliminated by the alpha-1-adrenoceptor blocker prazosin (10(-6) mol/l). alpha-1-Adrenoceptor stimulation apparently increased cellular dry weight by 10% (2, 18; 95% CI, P = 0.02). Changes in translocation of potassium and water must be considered as part of the alpha-1-adrenergic heart effects.

Cd(2+)-induced c-myc mRNA accumulation in NRK-49F cells is blocked by the protein kinase inhibitor H7 but not by HA1004, indicating that protein kinase C is a mediator of the response.

Cd2+ is a toxic cation that, at sublethal and marginally lethal levels, modifies cell growth and metabolism. Cd2+ exposure of NRK-49F cells results in inhibition of early EGF-induced DNA synthesis, but induction of delayed DNA synthesis; in stimulation of anchorage independent growth; in accumulation of specific oncogene mRNAs; and in an hypertrophic response. Determining whether specific signal transduction pathways (STPs) are involved in specific gene deregulation by cadmium in NRK-49F cells is important to defining possible mechanisms by which Cd2+ elicits these physiological responses. In this study it is shown that Cd2+ induces delayed myc (8-10 h) and jun (12 h) mRNA accumulation, as well as both early (0.5-1 h) and late (12 h) fos but not TGF beta mRNA accumulation. The times of appearance of Cd(2+)-induced c-fos, c-myc and c-jun expression are dose dependent. The Cd2+ induced accumulation of these specific mRNAs is insensitive to cycloheximide and therefore not due to preinduction of TGF beta or other gene-activating growth factors, but rather to direct induction of oncogene expression and/or mRNA stabilization. Accumulation of c-myc mRNA is shown further to be inhibited by the protein kinase inhibitor H7 but not HA1004, indicating a role for one or more protein kinases C in the STPs by which Cd2+ induces oncogene expression. Thapsigargin, a compound which stimulates increased cytosolic [Ca2+], induces c-myc expression also by an H7 sensitive, HA1004 insensitive pathway. These results suggest that Cd2+ acts through one or more defined signal transduction pathways involving specific protein kinases C to induce the accumulation of c-fos, c-myc and c-jun messenger RNAs.

Cadmium's action on NRK-49F cells to produce responses induced also by TGF beta is not due to cadmium induced TGF beta production or activation.

Transforming growth factor beta (TGF beta) is a multifunctional regulator of cell growth that has either a stimulatory or inhibitory effect on cell proliferation, depending on TGF beta concentration and on cell type, history and culture conditions. Cadmium mimics some of the effects of TGF beta in cultured cells. In this study the effects of Cd2+ and TGF beta on EGF-induced DNA synthesis in a clonal subpopulation (N1) of NRK-49F cells were compared. It was found that TGF beta 1 and cadmium both inhibit EGF-induced DNA synthesis and cell proliferation in a dose-dependent fashion, but that neither inhibits EGF-induced myc oncogene accumulation. TGF beta 1 and cadmium added at the same time as EGF or several hours after EGF addition showed similar inhibitory effects on EGF-induced [3H]Tdr incorporation, indicating that the inhibitory effect of TGF beta 1 and cadmium on EGF-induced DNA synthesis does not involve early G1 events. Rather, they occur in late G1, at the G1/S boundary or during S phase. Because of the similarities in nature and timing of the Cd2+ and TGF beta responses, the possibility that Cd2+ acts through stimulation of TGF beta production and/or activation was explored. It is shown in this paper however that TGF beta neutralizing antibody blocks the effects of TGF beta 1, but not the cadmium effects, on EGF-induced DNA synthesis, suggesting that cadmium is not functioning through activation or preinduction of TGF beta.

Buthionine sulfoximine-induced cytostasis does not correlate with glutathione depletion.

The effects of L-buthionine-(S,R)-sulfoximine (BSO) on the proliferation of normal rat kidney fibroblasts (NRK-49F) were determined and compared with the effects of BSO on cellular glutathione (GSH) content. The proliferation rate of exponentially growing NRK-49F cells was found to be slowed in 0.01 and 0.1 mM BSO and arrested in 1.0 and 10 mM BSO. There is no retardation in the proliferation of cells cultured in 0.001 mM BSO. However, varying BSO concentrations at and above 0.1 mM did not result in concordant differences in the rate and extent of GSH depletion. A dose-dependent effect of BSO on GSH levels was observed at BSO concentrations less than or equal to 0.01 mM. BSO was found also to inhibit epidermal growth factor (EGF)-induced DNA synthesis in NRK-49F cells arrested by serum deprivation in a dose-dependent pattern dissimilar to that of BSO-induced cellular GSH depletion. Removal of BSO allowed cells to resume proliferation. Further, growth-arresting BSO treatments were found to affect neither cell viability nor colony-forming efficiency. Addition of exogenous GSH or cysteine overcame BSO inhibition of EGF-induced DNA synthesis but not BSO depletion of cellular GSH levels. BSO was further found to inhibit the uptake of cysteine, cystine, and alpha-[1-14C]-methylaminoisobutyric acid (MeAIB) by the EGF-stimulated quiescent cells in a dose-dependent fashion. The results presented here thus demonstrate that BSO inhibits the proliferation of NRK-49F cells. This effect, however, does not correlate with BSO-induced cellular GSH depletion and is not due to an overt toxic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of opioid agonists selective for three subclasses of opioid receptors and one sigma receptor agonist on dopamine stimulated adenylate cyclase in rat caudate nucleus.

The adenylate cyclase in rat caudate nucleus homogenate could be stimulated by dopamine and less potently by the dopamine D1 receptor specific agonist SKF38393. Agonists selective for mu[D-Ala2, MePhe4Gly(ol)5]enkephalin (DAGO) and delta opioid receptors [D-Pen2, D-Pen5]enkephalin (dPen-dPen), inhibited the dopamine but not the dopamine D1 stimulated adenylate cyclase. The kappa opioid agonist, U69593, had no effect, probably due to low kappa receptor contents in rat caudate nucleus. 10(-4) M of the sigma receptor specific agonist, 1,3-di-o-tolylguanidine (DTG), potentiated the dopamine as well as the dopamine D1 stimulated adenylate cyclase while lower concentrations of DTG had no effect.

Cadmium induces hypertrophy accompanied by increased myc mRNA accumulation in NRK-49F cells.

Previous studies showed that Cd++ inhibits EGF-induced DNA synthesis but not EGF-induced myc mRNA accumulation or amino acid incorporation into protein in serum-starved NRK-49F cells. In this study, flow cytometry was used to analyze the DNA and protein content of individual cells stimulated with Cd++ and/or epidermal growth factor (EGF). myc oncogene expression in these cells was also measured. It was found that, in both parental NRK-49F cells and in a clonal subpopulation, N1, Cd++ induces an hypertrophic response. In parental NRK-49F cells, however, lower doses of Cd++ (0.5 microM) induced more pronounced hypertrophic responses than did higher doses (4 microM); whereas in N1 cells, the Cd+(+)-induced hypertrophic response shows a pattern of increasing response with doses of Cd++ from 0.5 to 4 microM. myc mRNA accumulation measured 2 hours after stimulation correlated with the hypertrophic responses in both NRK-49F cells and in N1 cells. The results show that Cd+(+)-induced hypertrophy in NRK-49F cells is associated with increased myc oncogene mRNA accumulation, indicating that cell proliferation and cell hypertrophy may in part share common activation pathways.

TGF beta elicits opposite responses in clonal subpopulations of NRK-49F cells.

Clonal subpopulations of NRK-49F cells were isolated and characterized for their responses to transforming growth factor beta (TGF beta). Two fibroblastic clones, N1 and N4, were found to have opposite TGF beta responses. TGF beta inhibits EGF-induced proliferation in growth-arrested, subconfluent monolayer cultures of N1 but not N4 cells. In contrast, TGF beta stimulates DNA synthesis and an increase in cell number in N4 but not N1 cells. The inhibitory effect of TGF beta on DNA synthesis in N1 cells is due not to modulation of the EGF receptor or other early G1 events. EGF-induced myc mRNA accumulation is not inhibited, and the action point for TGF beta inhibition of the entry into S of N1 cells is at the G1-S boundary.

Increased glutathione levels in quiescent, serum-stimulated NRK-49F cells are associated not with a response to growth factors but with nutrient repletion.

Treatment of quiescent cells with serum results concomitantly in an increase in cellular glutathione (GSH) content and growth stimulation. A possible association between the GSH increase and the growth response was examined by studying separately the effects of nutrients and growth factors on the levels of cellular GSH and proliferation of quiescent NRK-49F cells. The addition of fresh medium with 10% calf serum was found to result in both a twofold increase in cellular GSH and growth stimulation (DNA synthesis and cell proliferation). 10% calf serum alone, without fresh medium, stimulated cell growth but failed to cause a comparable increase in cellular GSH. The addition of fresh medium without 10% serum, and of 0.5 mM cysteine and glutamate, resulted in both instances in a marked increase in cellular GSH, but failed to stimulate cell growth. EGF, in contrast, induced a complete mitogenic response but did not increase cellular GSH. Finally, pretreatment with L-buthionine-(S,R)-sulfoximine (BSO), a specific inhibitor of GSH synthesis, decreased cellular GSH and inhibited EGF-induced DNA synthesis, but these two responses do not, in their dose dependency, correlate. The results obtained thus show that the increase in cellular GSH that occurs in quiescent, serum-stimulated NRK-49F cells is a result of nutrient repletion rather than mitogenic stimulation, and increased GSH levels do not necessarily precede DNA synthesis and mitosis.

Buthionine sulfoximine induced growth inhibition in human lung carcinoma cells does not correlate with glutathione depletion.

Treatment of A549 human lung carcinoma cells with L-buthionine-[S,R]-sulfoximine (BSO) results concomitantly in cellular glutathione (GSH) depletion and growth inhibition. The nature of BSO effects on cell growth and the relationships between BSO inhibition of cell growth and BSO effects on cellular GSH levels were determined in this study. A dose dependent effect of BSO on cell growth was observed, but this effect was found not to correlate with BSO effects on cellular GSH levels. Treatment with BSO for 60 h at concentrations of 5 and 10 mM was found to deplete cellular GSH at similar rates and to an undetectable level (below 0.5 nmol/mg protein). However, cessation of growth occurred in 10 mM BSO whereas growth continued at better than one half the control rate in 5 mM BSO. The results suggest there may be a distinct threshold level of intracellular GSH (on the order of or less than 0.5 nmol/mg protein) required for cell growth and for cells to protect themselves from the antiproliferative effects of BSO. At a concentration of 10 mM, BSO inhibited both DNA and protein synthesis and arrested growth of A549 cells throughout rather than at a specific phase of the cell cycle. BSO inhibition of growth was not, as indicated by colony-forming efficiency (CFE) and electron microscopy studies, accompanied by indications of cytotoxic effects. A stimulatory effect of 0.1 mM BSO on the growth of A549 cells was found also.

Cadmium inhibits EGF-induced DNA synthesis but increases cellular glutathione levels in NRK-49F cells.

The effects of cadmium (CdCl2) on epidermal growth factor (EGF) induced DNA synthesis and on cellular glutathione (GSH) content in growth-arrested NRK-49F cells were studied. The cadmium effects were compared with those of L-buthionine-(S,R)-sulfoximine (BSO). EGF at a concentration of 10 ng/ml was found to stimulate DNA synthesis (as judged by [3H]thymidine incorporation) in growth-arrested NRK-49F cells. CdCl2 inhibited this EGF-induced DNA synthesis in a dose-dependent fashion. It also increased significantly cellular GSH content in both growth arrested and EGF-stimulated NRK-49F cells. This effect of CdCl2 was contrary to that of BSO, which depleted cellular GSH. Although BSO both inhibited EGF-induced DNA synthesis and decreased cellular GSH content in EGF-stimulated NRK-49F cells, these two BSO effects showed dissimilar dose dependencies. BSO and CdCl2 together inhibited EGF-induced DNA synthesis in NRK-49F cells in an additive fashion. These results demonstrate that cadmium inhibition of EGF-induced DNA synthesis in NRK-49F cells is not due to an effect on cellular GSH content. Both cadmium and BSO inhibit EGF-induced DNA synthesis in NRK-49F cells, but probably through different mechanisms. Although GSH may be involved in regulation of DNA synthesis, BSO-induced inhibition of EGF-stimulated DNA synthesis in NRK-49F cells does not in its dose-dependency correlate with GSH depletion.

Cd++ inhibits EGF induced DNA synthesis but not EGF induced myc mRNA accumulation in serum starved NRK-49F cells.

Cd++ inhibits EGF-induced 3H-thymidine incorporation in serum deprived NRK-49F cells in a dose dependent pattern. The underlying mechanisms for this inhibition are largely unknown. EGF-induced myc mRNA accumulation in NRK-49F cells and the effects of Cd++ on this response were examined under conditions that result in partial or complete inhibition of EGF-induced DNA synthesis. It was found that doses of Cd++ that inhibit EGF-induced DNA synthesis do not inhibit EGF-induced protein synthesis and myc mRNA accumulation. Cd++ doses of 0.5 microM and 1 microM were found actually to increase EGF-induced myc mRNA accumulation and amino acid incorporation. These results show that the effect of Cd++ on EGF-induced DNA synthesis is not due to inhibition of entrance into G1, but rather that Cd++ acts on events subsequent to myc accumulation; that is, events associated with either G1 progression, entry into S or DNA synthesis.

Diamide reduces cadmium accumulation by human lung carcinoma A549 cells.

Human lung carcinoma A549-T27 cells were used to determine the effect of diamide on cadmium accumulation. Treatment of the cells with diamide decreased their cellular glutathione content to 51.6 +/- 7% of control and significantly decreased their cadmium accumulation both as a function of time and as a function of Cd2+ concentration. Verapamil also decreased cadmium accumulation. Its effect compares well in magnitude with that which resulted from diamide treatment. No additive effect was observed when the cells were simultaneously treated with diamide and verapamil. The results suggest that a change in the GSH/GSSG ratio affects cadmium uptake. Further, calcium channels may be involved in cadmium uptake by A549-T27 cells in a fashion that is dependent on sulfhydryl status.