Mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitors restore anoikis sensitivity in human breast cancer cell lines with a constitutively activated extracellular-regulated kinase (ERK) pathway

Anchorage-independent growth is a hallmark of oncogenic transformation. We reported that the mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor U0126 inhibited anchorage-independent growth of Ki-ras-transformed rat fibroblasts by simultaneously blocking both extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR)-p70(S6K) pathways. Here, we examined the effects of U0126 on the growth of eight human breast cancer cell lines. U0126 selectively repressed anchorage-independent growth of MDA-MB231 and HBC4 cells, two lines with constitutively activated ERK. Loss of contact with substratum triggers apoptosis in many normal cell types, a phenomenon termed anoikis. U0126 sensitized MDA-MB231 and HBC4 to anoikis, i.e., upon treatment with U0126, cells deprived of anchorage entered apoptosis, whereas adherent cells remained viable. Another MEK inhibitor PD98059 also induced anoikis sensitivity in MDA-MB231 cells but not in HBC4 cells. However, HBC4 cells were sensitized to anoikis when PD98059 was combined with the mTOR inhibitor rapamycin. To study the biochemical basis for induction of anoikis sensitivity, we examined the effects of the MEK inhibitors on ERK and p70(S6K) pathways in anchored versus nonanchored cells. As in Ki-ras-transformed rat fibroblasts, U0126 reduced activation of both ERK and p70(S6K) in MDA-MB231 and HBC4 cells, irrespective of anchorage. PD98059, in anchored cells, was more selective for the ERK pathway and did not significantly block the p70(S6K) pathway. Removal of anchorage substantially sensitized p70(S6K) to PD98059 in MDA-MB231 cells, whereas p70(S6K) in suspended HBC4 cells remained fairly refractory. U0126 was either without effect or less inhibitory on p70(S6K) in MDA-MB453 and SKBR3, two cell lines in which anoikis sensitivity was not induced. Thus, susceptibility of the p70(S6K) pathway to MEK inhibitors appeared to be an important determinant of anoikis sensitivity. The results indicate that concurrent inhibition of MEK-ERK and mTOR-p70(S6K) pathways induces apoptosis in MDA-MB231 and HBC4 cells when cells are deprived of anchorage but not when anchored. Inhibitors of MEK-ERK and mTOR-p70(S6K) pathways may provide a therapeutic strategy to selectively target neoplasms proliferating at ectopic locations, with acceptable effects on normal cells in their proper tissue context.

Effects of hibarimicins and hibarimicin-related compounds produced by Microbispora on v-Src kinase activity and growth and differentiation of human myeloid leukemia HL-60 cells

We studied the effects of hibarimicins and hibarimicin-related compounds produced by Microbispora rosea subsp. hibaria [glycosides (hibarimicins A, B, C, D, E, G, H and I) and aglycon (hibarimicinone)] or compounds produced by its mutants [glycosides (HMP-P4 and -Y6), aglycons (HMP-P1 and -Y1) and shunt products (HMP-M1, M2, M3 and -M4)] on v-Src tyrosine kinase and growth and differentiation of human myeloid leukemia HL-60 cells. Among them, hibarimicin B was a strong and the most selective v-Src kinase inhibitor with differentiation inducing activity of HL-60 cells. Hibarimicin E similarly induced HL-60 cell differentiation but had no v-Src kinase inhibitory activity. Hibarimicinone was the most potent v-Src kinase inhibitor, although less selective, and did not induce differentiation of HL-60 cells. Hibarimicin B competitively inhibited ATP binding to the v-Src kinase, but hibarimicinone showed noncompetitive inhibition. These two compounds, however, showed similar mixed types of inhibition against a Src substrate binding to the v-Src kinase. Altogether, these results suggest that signaling molecules other than Src might be more important in the differentiation induction of HL-60 cells.

Spin-orbit coupling in the Mott insulator Ca(2)RuO(4)

O 1s x-ray absorption study of the Mott insulator Ca(2)RuO(4) shows that the orbital population of the 4d t(2g) band dramatically changes with temperature. In addition, spin-resolved circularly polarized photoemission study of Ca(2)RuO(4) shows that a substantial orbital angular momentum is induced in the Ru 4d t(2g) band. Based on the experimental results and model Hartree-Fock calculations, we argue that the cooperation between the strong spin-orbit coupling in the Ru 4d t(2g) band and the small distortion of the RuO(6) octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.

Left ventricular epicardial outflow tract tachycardia: a new distinct subgroup of outflow tract tachycardia

The present study investigated the incidence and ECG characteristics of ventricular tachycardias (VTs) originating from the left ventricular (LV) epicardium. Thirty-one consecutive patients with VT or premature ventricular contraction originating from the outflow tract (OT-VT) underwent catheter ablation. Twenty-one OT-VTs were ablated from the endocardium in the right ventricular (RV) OT and 3 were ablated from the endocardium in the LVOT. In the remaining 7 patients, 4 (13%) OT-VTs were LV epicardial in origin, and 1 of these was ablated from the left sinus of Valsalva. The ECG characteristics of OT-VT of epicardial origin included prominent tall R-waves in the inferior leads, an R-wave in V1 and an S-wave in V2, precordial R-wave transition in V2-4, a deep QS-wave in aVL, and no S-wave in V6. In addition, there was an atypical left bundle branch block morphology with an inferior axis. These findings were observed during pacing from several sites in the LV epicardium. Furthermore, pacing from the left sinus of Valsalva caused a relatively tall R in V1, deep S-wave in V2 and a tall R-wave with a shallow S-wave in V3, as well as tall R-waves in the inferior leads, which represented intermediate characteristics between RV endocardial OT-VT and LV endocardial OT-VT. In conclusion, OT-VT originating from the LV epicardium is not uncommon and has characteristic ECG findings. Some of them can be ablated from the left sinus of Valsalva.

Identification and quantification of chlorinated bisphenol A in wastewater from wastepaper recycling plants

Chlorinated derivatives of bisphenol A were detected in the final effluents of eight paper manufacturing plants in Shizuoka, Japan, where thermal paper and/or other printed paper is used as the raw material. Their amounts were determined by gas chromatography/mass spectrometry (GC/MS) after treatment with N, O-bis(trimethylsilyl)trifluoroacetamide, and ranged from traces to 2.0 microg/l. They are likely produced by chlorination of bisphenol A, which was released into the effluents from the pulping process of wastepaper, during or after bleaching with chlorine.

Chemokine expression in coronary circulation after coronary angioplasty as a prognostic factor for restenosis

Recent studies have clarified the significance of chemokines in cardiovascular diseases, such as development of atherosclerosis, atheromatous plaque rupture and restenosis after coronary angioplasty. We investigated changes in chemokine expression in the coronary circulation induced by percutaneous transluminal coronary angioplasty (PTCA) and their clinical significance. We examined 40 patients with angina pectoris who underwent elective PTCA for isolated stenotic lesions of the left coronary artery. Eight patients received PTCA only, 14 percutaneous transluminal rotational atherectomy and 18 stent implantation. Venous blood samples were obtained from the coronary sinus before, and immediately after as well as 4 and 24 h after PTCA. Plasma levels of interleukin (IL)-8, macrophage-colony stimulating factor (M-CSF) and monocyte chemoattractant protein-1 (MCP)-1 were measured by enzyme-linked immunosorbent assay. Plasma levels of M-CSF in the coronary sinus blood showed significant increases 4 and 24 h after PTCA. On the other hand, plasma MCP-1 levels did not change significantly during a 24-h observation period after PTCA. Immunoreactive IL-8 was not detected in any patients before or after PTCA. A significant positive correlation was found between plasma M-CSF levels 24 h after PTCA and late loss index 6 months after the procedure. Plasma levels of M-CSF 24 h after PTCA were significantly higher in patients with than in those without late restenosis. PTCA induced increases in plasma levels of M-CSF in the coronary circulation. Increased M-CSF expression may be involved in neointima formation at injured vessels through activation of mononuclear phagocytes.

Identification of co-mutagenic chlorinated harmans in final effluent from a sewage treatment plant

Harman (1-methyl-9H-pyrido[3,4-b]indole) reacted readily with sodium hypochlorite in an aqueous medium to give the mono-chlorinated derivatives, which reportedly have greater co-mutagenic activity than harman in the presence of o-toluidine toward Salmonella typhimurium TA 98 with S9 mix. Mono-chlorinated harmans were detected by concentration using blue rayon (BR) and GC/MS analysis in the final effluent from a sewage treatment plant in Shizuoka, Japan. The amounts adsorbed for 24h were 1-45ng/gBR for mono-chlorinated harman and 110-730ng/gBR for harman.

Chlorination of harman and norharman with sodium hypochlorite and co-mutagenicity of the chlorinated products

Harman and norharman are widely distributed in the environment and consequently contaminate in domestic waste-water. It has been reported that they have co-mutagenic activity in the presence of non- mutagenic aromatic amines such as aniline and o-toluidine with S9 mix. When these beta-carbolines were treated with sodium hypochiorite under mild conditions, chlorinated derivatives were produced. Among them, 6-chloroharman and 6-chloronorharman showed much more potent co-mutagenic activities than harman and norharman in the presence of o-toluidine toward Salmonella typhimurium TA98 with S9 mix. These results suggest that the chlorination of harman and norharman occurs during disinfection at the sewage plant to produce potent co-mutagens that contaminate river water.

Release of endothelin 1 and angiotensin II induced by percutaneous transluminal coronary angioplasty

Endothelial injury plays critical roles in acute and chronic complications after percutaneous transluminal coronary angioplasty (PTCA). We investigated coronary endothelial injury and the release of vasoactive substances induced by PTCA. We examined 44 patients with ischemic heart disease who underwent elective PTCA to isolated stenotic lesions in left coronary arteries. Eleven patients received balloon angioplasty (BA), 14 percutaneous transluminal rotational atherectomy (PTRA), and 19 stent implantation. Blood samples were drawn from the coronary sinus immediately before and after as well as 4 hr and 24 hr after PTCA. Plasma levels of endothelin (ET) 1, angiotensin (ANG) II, von Willebrand factor (vWF), and thrombomodulin (TM) were measured. Seven control subjects who underwent diagnostic coronary angiography (CAG) were used as controls. In all patients, ET-1 levels in the coronary sinus blood significantly increased immediately after PTCA. ANG II levels and vWF activity showed significant increases 4 hr after PTCA. Changes in levels of these markers were similar among the BA, PTRA, and stent groups. TM levels were elevated in all groups of patients, including those simply undergoing diagnostic CAG. Changes in ET-1, ANG II, and vWF levels in the coronary sinus reflect coronary endothelial injury induced by PTCA.

Novel compounds, '1,3-selenazine derivatives' as specific inhibitors of eukaryotic elongation factor-2 kinase

The inhibitory activities of 5,6-dihydro-4H-1,3-selenazine derivatives on protein kinases were investigated. In a multiple protein kinase assay using a postnuclear fraction of v-src-transformed NIH3T3 cells, 4-ethyl-4-hydroxy-2-p-tolyl-5, 6-dihydro-4H-1,3-selenazine (TS-2) and 4-hydroxy-6-isopropyl-4-methyl-2-p-tolyl-5,6-dihydro-4H-1, 3-selenazine (TS-4) exhibited selective inhibitory activity against eukaryotic elongation factor-2 kinase (eEF-2K) over protein kinase A (PKA), protein kinase C (PKC) and protein tyrosine kinase (PTK). In further experiments using purified kinases, TS-2 (IC(50)=0.36 microM) and TS-4 (IC(50)=0.31 microM) inhibited eEF-2K about 25-fold more effectively than calmodulin-dependent protein kinase-I (CaMK-I), and about 6-fold (TS-2) or 33-fold (TS-4) more effectively than calmodulin-dependent protein kinase-II (CaMK-II), respectively. TS-2 and TS-4 showed much weaker inhibitory activity toward PKA and PKC, while TS-4, but not TS-2, moderately inhibited immunoprecipitated v-src kinase. TS-2 (10.7-fold) and TS-4 (12.5-fold) demonstrated more potent and more specific eEF-2K inhibitory activity than rottlerin, a previously identified eEF-2K inhibitor. TS-2 inhibited ATP or eEF-2 binding to eEF-2K in a competitive or non-competitive manner, respectively. In cultured v-src-transformed NIH3T3 cells, TS-2 also decreased phospho-eEF-2 protein level (IC(50)=4.7 microM) without changing the total eEF-2 protein level. Taken together, these results suggest that TS-2 and TS-4 are the first identified selective eEF-2K inhibitors and should be useful tools for studying the function of eEF-2K.

Interleukin 6 expression in coronary circulation after coronary angioplasty as a risk factor for restenosis

OBJECTIVE

To investigate changes in cytokine expression in the coronary circulation induced by percutaneous transluminal coronary angioplasty (PTCA).

METHODS

The study involved 32 patients with ischaemic heart disease who underwent elective PTCA for isolated stenotic lesions of the left coronary artery. Ten patients had plain old balloon angioplasty, 10 had percutaneous transluminal rotational atherectomy, and 12 had stent implantation. Blood samples were drawn from the coronary sinus before and immediately after PTCA. Plasma concentrations of interleukin 6 (IL-6), platelet derived growth factor (PDGF), monocyte chemoattractant protein 1 (MCP-1), and macrophage coronary stimulating factor (M-CSF) were measured. The patients were scheduled for follow up angiography six months after PTCA. Late loss index was calculated using quantitative coronary angiography.

RESULTS

IL-6 concentrations in coronary sinus blood increased immediately after PTCA (p < 0.001), but there was no change in PDGF, MCP-1, or M-CSF. There was a positive correlation between changes in IL-6 concentrations immediately after PTCA and late loss index six months after PTCA (r = 0.73, p < 0.001). IL-6 concentrations in coronary sinus blood were higher in patients with late restenosis than in those without restenosis (p < 0.001).

CONCLUSIONS

PTCA induces IL-6 production in the coronary circulation. This may induce subsequent inflammatory responses in injured vessels and play an important role in late restenosis after PTCA.

U0126 reverses Ki-ras-mediated transformation by blocking both mitogen-activated protein kinase and p70 S6 kinase pathways

U0126, a recently introduced mitogen-activated protein kinase [corrected] (MAPK)/extracellular signal-regulated kinase kinase inhibitor reversed morphology and inhibited anchorage-independent growth of Ki-ras-transformed rat fibroblasts. Immunoblot analyses with phosphospecific antibodies indicated that in addition to MAPK, U0126 suppressed activation of p70(S6K), but not Akt, at concentrations at which it normalized the transformed phenotypes. Another MAPK/extracellular signal-regulated kinase kinase inhibitor, PD98059, showed only marginal effects on p70S6K phosphorylation and did not effectively block Ki-ras-induced transformation. However, simultaneous inhibition of the MAPK pathway and the p70S6K pathway by PD98059 in conjunction with the p70S6K inhibitor rapamycin essentially restored the normal phenotype. U0126 or the combination of PD98059 and rapamycin flattened morphology of v-src-transformed cells, but did not reverse anchorage independence, although activation of both MAPK and p706K was blocked. The results suggest that normalization of Ki-ras-induced transformed phenotypes by U0126 is a consequence of concurrent inhibition of the MAPK and p70S6K pathways. Intervention of other pathway(s) appears to be required to completely antagonize transformation by v-src. Simultaneous blockade of more than one signal transduction pathway by combining selective inhibitors might be effective in suppressing uncontrolled tumorigenic growth.

Assessment of coagulation and platelet activation in coronary sinus blood induced by transcatheter coronary intervention for narrowing of the left anterior descending coronary artery

Influences of recently developed methods for coronary intervention on hemostasis in the coronary circulation are unclear. The objective of this study was to investigate changes in coagulation and platelet activation in the coronary circulation induced by percutaneous transluminal coronary angioplasty (PTCA). We studied 35 patients with coronary heart disease who underwent elective PTCA to isolated stenotic narrowing of left coronary arteries. Seven patients received only PTCA, 12 underwent percutaneous transluminal rotational atherectomy (PTRA), and 16 underwent stent implantation. Blood samples were drawn from the coronary sinus immediately before and after as well as 4 and 24 hours after PTCA. Plasma levels of tissue factor (TF), thrombin-antithrombin III complex, plasminogen activator inhibitor (PAI)-1, tissue plasminogen activator (t-PA), beta-thromboglobulin, and platelet factor 4 were measured by enzyme-linked immunosorbent assay. In all patients, TF levels in the coronary sinus blood showed significant increases 4 and 24 hours after PTCA and thrombin-antithrombin III complex levels showed significant increases 24 hours after PTCA. PAI-1 showed significant increases 24 hours after PTCA and t-PA showed significant increases 4 and 24 hours after PTCA. Changes in levels of these markers by PTCA were similar among the 3 groups. In PTRA, levels of beta-thromboglobulin and platelet factor 4, markers of platelet activation, increased immediately after the procedure and returned to baseline levels after 4 hours. PTCA induced increases in blood coagulation and fibrinolysis in the coronary circulation. PTRA caused a marked but transient activation of platelets. These changes may contribute to acute complications during the procedure.

Antagonistic effect of N-methyltyramine on alpha2-adrenoceptor in mice

We examined the effect of N-methyltyramine (NMT) on alpha2-adrenoceptor. NMT (10(-8)-10(-3) M) inhibited the binding of [3H]p-aminoclonidine to alpha2-adrenoceptor dose-dependently. However, the IC50 value for NMT (5.53 x 10(-6) M) was higher than that for RX821002, an alpha2-adrenoceptor antagonist (1.07 x 10(-8) M). RX821002 (5 mg/kg, i.p.) inhibited hypermotility induced by scopolamine (8 mg/kg, s.c.) in male ddY mice. NMT (20 or 100 mg/kg, i.p.) was found to have a dose-dependent inhibitory effect similar to that of RX821002. These findings indicate that NMT has the properties of an alpha2-adrenoceptor antagonist. However, the affinity of NMT for alpha2-adrenoceptor is weaker than that of RX821002.

Studies of the active substances in herbs used for hair treatment. III. Isolation of hair-regrowth substances from Polygara senega var. latifolia TORR. et GRAY

Four active principles, 1, 2, 3 and 4, were isolated from Polygara senega var. latifolia TORR. et GRAY by a combination of partition and column chromatography on silica gel and octadecyl silica gel (ODS), monitored by a hair-regrowth activity assay. Compounds 1, 2, 3 and 4 were identified as senegose A, senegin II, senegin III, and senegasaponin b by comparison of their spectral data with those of authentic samples.

Increased serum soluble Fas in patients with Graves' disease

We addressed the role of soluble Fas (sFas), which suppresses Fas-mediated apoptosis, in the pathogenesis of Graves' disease (GD). The serum concentration of sFas was measured by enzyme-linked immunosorbent assay and the expression of sFas mRNA in thyroid tissues by reverse transcriptase-polymerase chain reaction. The serum concentration of sFas was significantly increased in untreated GD (mean+/-SD: 1.57+/-0.48 ng/mL) compared to age-matched control subjects (0.77+/-0.46 ng/mL). The serum sFas level tended to decrease after the medication of antithyroid drugs for 6 to 8 weeks and was significantly decreased in patients who were euthyroid for more than 3 years (0.98+/-0.23 ng/mL), compared to that in untreated GD. The concentration of serum sFas was significantly correlated with anti-thyrotropin (TSH) receptor antibody titers, but not with the other clinical parameters (free triiodothyronine [FT3], free thyroxine [FT4], TSH, antithyroglobulin antibody titer, antimicrosomal antibody titer, or 123I uptake). The sFas mRNA was detected in thyroid tissue, cultured thyrocytes, and intrathyroidal lymphocytes. sFas was detected in supernatant of cultured thyrocytes from patients with GD. Its production by thyrocytes was induced by culture with interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha). The present study confirms serum sFas increases in GD and provides evidence of local production of sFas by thyrocytes and its regulation by cytokines. These data suggest that sFas may play a role in the pathogenesis of GD.

Isolation from beer and structural determination of a potent stimulant of gastrin release

Beer was subjected to five successive chromatographic procedures to isolate the gastrin release-inducing activity, guided by bioassay of the fractions in anaesthetized Donryu rats. The procedures were: (1) hydrophobic interaction chromatography (aqueous effluent with an HP20 column); (2) weak cation-exchange chromatography (1 M acetic acid eluate with a CM Sephadex C-25 column); (3) gel filtration (methanol eluate with a Sephadex LH-20 column); (4) same as (2); (5) high-performance liquid chromatography (YMC-Pack ODS-AM with 7% acetonitrile-0.01 M HCl). The active component finally isolated had a specific activity approximately 10000 times higher than that of beer. It was identified by means of mass, 1H- and 13C-nuclear magnetic resonance spectral analyses as N-methyltyramine (NMT). The dose of NMT giving maximal gastrin-releasing activity was 25 microg/kg, and the 50% effective dose was approximately 10 microg/kg on oral administration to rats. NMT was isolated and identified as a gastrin release inducer in beer. Its concentration in beer is sufficient to account for most of the activity of beer.

Measurement of red blood cell zinc concentration with Zn-test kit: discrimination between hyperthyroid Graves' disease and transient thyrotoxicosis

We have previously reported in patients with hyperthyroidism that the red blood cell (RBC) zinc (Zn) concentration reflects the mean thyroid hormone concentration over the preceding months. In the present study, the concentration of RBC Zn was measured by a simple and easy method with a Zn-test Wako kit. Within-run and between-run precision were 1.4% and 1.3%, respectively. The relationship between RBC concentration and dilution was linear. The average recovery was 103%. A good correlation (r=0.97) was obtained between this method and atomic absorption spectrophotometry. The mean concentration of RBC Zn in 39 euthyroid controls was 12.6 +/- 1.3 mg/l, ranging from 10.4 to 15.1 mg/l. The RBC Zn concentrations in 38 patients with Graves' disease, in 10 patients with silent thyroiditis and in 3 patients with gestational thyrotoxicosis were 7.3 +/- 1.6 (3.2-9.8), 12.0 +/- 1.6 (9.5-14.2) and 11.8 +/- 1.7 (10.5-13.7) mg/l, respectively. The concentration of RBC Zn was able to differentiate hyperthyroid Graves' disease from transient thyrotoxicosis except in 1 case and was a better index than TSH-binding inhibitory immunoglobulin. These results indicate that measuring RBC Zn with the Zinc-test Wako kit is very useful in differentiating hyperthyroid Graves' disease from transient thyrotoxicosis.

Effect of herbimycin A on tyrosine kinase receptors and platelet derived growth factor (PDGF)-induced signal transduction

Herbimycin A is widely used as an inhibitor of Src family protein tyrosine kinases but is also reported to induce the downregulation of epidermal growth factor (EGF) receptor number in A431 cells without inhibiting its tyrosine kinase activity. To determine the specificity of the receptor downregulation, we examined its effect on a variety of cell lines which express different levels of EGF receptor and on other tyrosine kinase receptors. Long-term herbimycin A treatment decreased the amounts of all the tyrosine kinase receptors examined in a dose-dependent manner. It also reduced ligand-stimulated receptor autophosphorylation in accordance with the reduction in the receptor level. Herbimycin A inhibited platelet derived growth factor (PDGF)-induced tyrosine phosphorylation of cellular proteins and DNA synthesis in NIH3T3 cells but did not affect the serum-stimulated DNA synthesis. PDGF-induced tyrosine phosphorylation and activation of c-Src was inhibited but the protein level of c-Src was not reduced by herbimycin A. The reduced level of c-Src kinase activity correlated with the levels of both PDGF receptor and DNA synthesis. These results indicate that the herbimycin A treatment selectively downregulates receptor tyrosine kinases, independent of the number of receptors, and suggest that c-Src is to some degree involved in the selective inhibition of PDGF-induced mitogenesis by herbimycin A.

1a-docosahexaenoyl mitomycin C: a novel inhibitor of protein tyrosine kinase

A series of derivatives of mitomycin C conjugated with various fatty acids at position 1a was synthesized and the effect of these compounds on protein kinase activities was evaluated. 1a-Docosahexaenoyl mitomycin C (DMMC) selectively inhibited protein tyrosine kinase (PTK) activity in the postnuclear fraction of v-src-transformed NIH 3T3 cells although neither derivatives conjugated with other fatty acids or docosahexaenoic acid or mitomycin C did not. DMMC inhibited the activity of calmodulin-dependent kinase III and protein kinase A very weakly, and only barely affected protein kinase C activity. DMMC also attenuated autophosphorylation of immunoprecipitated p60v-src irreversibly. The addition of thiol compounds to the reaction mixture reversed the inhibition by DMMC, suggesting that some thiol moiety of PTK protein might be involved. DMMC also inhibited kinase activity of p210bcr-abl immunoprecipitated from the lysate of K562 cells. These results indicate that DMMC is a novel inhibitor of PTK.

Inhibitory effects of 5-S-GAD on phosphorylation of V-SRC and BCR-ABL tyrosine kinase

We examined the inhibitory effects of N-beta-alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine (5-S-GAD), a novel antibacterial substance from the immunized adult Sarcophaga peregrina (flesh fly), on protein phosphorylation using immune complexes of protein tyrosine kinases (PTKs) with anti-PTKs monoclonal antibody. We found that 5-S-GAD directly inhibited not only tyrosine phosphorylation of PTK p60(v-src), but also tyrosine phosphorylation of PTK p210(BCR-ABL). The inhibitory potency of 5-S-GAD was comparable to that of radicicol and herbimycin A of PTK inhibitor.

Effects of thyroid hormone on carbonic anhydrase I gene expression in human erythroid cells

Individuals with hyperthyroidism exhibit concentrations of carbonic anhydrase I (CAI) in red blood cells that reflect the integrated serum thyroid hormone concentration over the preceding few months. Furthermore, triiodothyronine T3, at a physiological free concentration, decreases the CAI concentration in both human erythroleukemic YN-1 cells and burst-forming unit-erythroid (BFU-E)-derived cells. In the present study, the effect of T3 on CAI mRNA levels in various human erythroleukemic cell lines (YN-1, HEL and KU-812) and BFU-E-derived cells was studied. Northern analysis of RNA extracted from erythroid cells revealed a CAI mRNA of 1.5 kilobases. T3 significantly decreased the levels of CAI mRNA in YN-1 and BFU-E-derived cells in a dose-dependent manner. Incubation of T3-stimulated cells with actinomycin D prevented the decrease in CAI mRNA levels. By contrast, T3 had no effect on either the concentrations of CAI or the levels of CAI mRNA in HEL and KU-812 cells. These results suggest that YN-1 and BFU-E-derived cells may be useful models for investigating T3 actions on CAI mRNA in human cells.

Left ventricular function and coagulation activity in healed myocardial infarction

We investigated the plasma levels of molecular markers for the thrombotic and fibrinolytic status in patients with healed myocardial infarction to determine the relation between left ventricular (LV) function and coagulation activity. Our findings demonstrated that the coagulation activity was increased in patients with healed myocardial infarction along with LV dysfunction, suggesting that anticoagulant therapy is considered in patients with severe LV dysfunction to prevent systemic thromboembolism.

Hyperthyroid Graves' disease and primary hypothyroidism caused by TSH receptor antibodies in monozygotic twins: case reports

A 33-year-old woman with signs and symptoms of hypothyroidism, including increased thyroid stimulating blocking antibody (TSBAb) activity, was referred for treatment by her local physician. Her monozygote twin was treated for hyperthyroid Graves' disease 10 years earlier. This case of hyperthyroidism and hypothyroidism in identical twins suggests the involvement of environmental factors in the pathogenesis of autoimmune thyroid diseases.

Effect of mitral regurgitation on coagulation activity in atrial fibrillation

We measured the plasma levels of molecular markers for thrombotic and fibrinolytic status in patients with nonrheumatic atrial fibrillation (AF) to investigate the relation between coagulation activity and mitral regurgitation (MR). Our findings demonstrated that a greater degree of MR was associated with less coagulation activity in patients with nonrheumatic AF, suggesting that MR protects against left atrial thrombus and systemic thromboembolism.

Role of thyroid-stimulating blocking antibody in patients who developed hypothyroidism within one year after 131I treatment for Graves' disease

OBJECTIVE

We recently reported that thyroid-stimulating blocking antibody (TSBAb) may not contribute to the development of hypothyroidism more than six years after 131I treatment. In the present study, we attempted to determine whether hypothyroidism that develops within a shorter period of time following 131I therapy is associated with TSBAb.

DESIGN

Retrospective study.

PATIENTS

Sera were obtained from 8 patients who developed hypothyroidism within 6 months after 131I therapy (Group 1), 8 patients who became euthyroid one year after 131I therapy (Group 2), and 7 patients who developed transient hypothyroidism (Group 3).

MEASUREMENTS

Thyroid stimulating antibody (TSAb) activity was measured as the amount of cyclic adenosine monophosphate (cAMP) produced by cultured FRTL-5 cells, and TSBAb activity as the inhibition of cAMP produced in response to 100 mU/l bovine TSH.

RESULTS

At about 3 months after 131I treatment, TSAb activity increased significantly in Groups 2 and 3, but did not change in Group 1. In contrast, TSBAb activity in Group 1 increased significantly and was positive in 6 patients at that time. At 12-18 months after 131I treatment, TSBAb activity tended to decrease and remained positive in 3 patients but became negative in 3 patients. It did not change in the patients in Groups 2 and 3. The patients in Group 1 were treated with levothyroxine, 75-125 micrograms/day. Levothyroxine was discontinued in the 3 patients whose TSBAb activity disappeared. Two of them remained euthyroid, and 1 became hypothyroid.

CONCLUSION

Results indicate that the hypothyroidism that develops within a short time after 131I treatment may be caused by TSBAb activity. Thyroid function may be recovered when TSBAb activity disappears.

Interaction of the DNA topoisomerase II catalytic inhibitor meso-2,3-bis(3,5-dioxopiperazine-1-yl)butane (ICRF-193), a bisdioxopiperazine derivative, with the conserved region(s) of eukaryotic but not prokaryotic enzyme

ICRF-193 [meso-2,3-bis(3,5-dioxopiperazine-1-yl)butane], a bisdioxopiperazine compound, has been shown to be a catalytic inhibitor of DNA topoisomerase II by stabilizing the enzyme in the form of a closed "protein clamp," an intermediate form in the catalytic cycle (Roca et al., Proc Natl Acad Sci USA 91: 1781-1785, 1994). In view of its usefulness as a probe in the functional analysis of the enzyme, we tried further to define the domain(s) of the enzyme interacting with the drug by examining its inhibitory activity on type II topoisomerases from various species of eukaryotes and prokaryotes. ICRF-193 inhibited the enzyme from yeast, fly, frog, plant, and mammals at IC50 values in the range of 1-13 microM. Experiments using fission yeast truncated mutant type II enzyme lacking both amino-terminal 74 amino acids and carboxy-terminal 265 amino acids revealed that ICRF-193 interacts with the 125 kDa "core" polypeptide of the enzyme. In contrast, prokaryotic type II enzymes, Escherichia coli DNA gyrase, topo IV, and phage T4 topo, were not affected by the drug. From these results, the domain(s) common to eukaryotic but not to prokaryotic type II enzymes interacting with ICRF-193 was speculated.

Effect of mitral valvuloplasty in mitral stenosis on coagulation activity

We investigated the plasma levels of molecular markers for the status of thrombin generation and fibrinolysis in patients with mitral stenosis before and after percutaneous mitral valvuloplasty. Our results show that percutaneous mitral valvuloplasty results in decreased coagulation activity, suggesting that percutaneous mitral valvuloplasty is also useful for prevention of systemic embolism in patients with mitral stenosis.

Inhibition of anchorage-independent growth of ras-transformed cells on polyHEMA surface by antisense oligodeoxynucleotides directed against K-ras

We examined the effect of antisense oligodeoxynucleotides (AS ODNs) directed against v-Ki-ras on the anchorage-independent growth of v-Ki-ras-transformed rat fibroblasts using plates coated with an antiadhesive polymer, poly(2-hydroxyethyl methacrylate) (polyHEMA). Among AS ODNs tested, 17mer AS ODN centered around codon 12 of v-Ki-ras inhibited the v-Ki-Ras expression and v-Ki-Ras-induced anchorage-independent growth, while its sense sequence did not affect it. Using polyHEMA plates, the direct addition of AS ODNs to the cells growing anchorage-independently and various treatment schedules of AS ODNs are now available to identify the most desirable conditions for AS ODNs treatment.

The development of transient hypothyroidism after iodine-131 treatment in hyperthyroid patients with Graves' disease: prevalence, mechanism and prognosis

OBJECTIVE

Recovery of thyroid function in patients following hypothyroidism induced by 131I therapy for Graves' disease has been described, but only a few detailed clinical and biochemical studies of this phenomenon (transient hypothyroidism) have been published. The prevalence, mechanism, and final outcome of transient hypothyroidism in 260 patients with Graves' disease treated with 131I was studied.

DESIGN

A retrospective study.

PATIENTS

Two hundred sixty patients with Graves' disease, treated with 131I between 1 and 15 years previously, were categorized into 4 groups according to their thyroid function during and 1 year after therapy (Group 1: permanent hypothyroidism, 28 patients; Group 2: transient hypothyroidism, 39 patients; Group 3: euthyroidism without transient hypothyroidism, 83 patients; Group 4: hyperthyroidism, 110 patients).

MEASUREMENTS

We compared total T4, total T3, TSH, anti-thyroglobulin (TGHA) and anti-microsomal (MCHA) antibodies, the TSH-binding inhibitory immunoglobulin (TBII) index, thyroid weight, dose of 131I, and 24-hour 131I uptake as pretreatment variables. The mean time for permanent hypothyroidism to develop was estimated by the Kaplan-Meier product limit method. The TBII index and thyroid stimulating antibody (TSAb) activity were measured in seven patients from Group 1 and in nine patients from Group 2 at the time that they became hypothyroid.

RESULTS

Hypothyroidism developing within 12 months of therapy was transient in 58% (39/67) of patients. No pretreatment variables were found to differ between patients with and without transient hypothyroidism. The mean estimated time between therapy and the development of permanent hypothyroidism was 96 months in Group 2; this time interval was significantly shorter than 126 months in Group 3 and 129 months in Group 4 (P < 0.05, P < 0.01, respectively). TSAb activity was > 500% In 78% (7/9) of patients from Group 2, which was significantly higher than that found (14%, 1/7) in Group 1.

CONCLUSIONS

These results indicate that (1) more than half the patients who developed hypothyroidism within 6 months after 131I treatment for Graves' disease recovered spontaneously, (2) TSAb activity might play some role in the recovery of transient hypothyroidism, and (3) the development of transient hypothyroidism may influence long-term thyroid function.

Circadian variation in incidence of cardioembolism

Cardioembolism is most likely to occur after waking in the morning. The identification of periods of high risk for cardioembolism may have important therapeutic implications, such as matching drug effects with vulnerability.

Relationship between thyroid-stimulating antibodies and thyrotropin-binding inhibitory immunoglobulins years after administration of radioiodine for Graves' disease: retrospective clinical survey

Thyroid-stimulating antibody (TSAb) activity and the TSH-binding inhibitory immunoglobulin (TBII) index were assessed in 158 patients with Graves' disease who had been treated with 131I 6-14 years earlier. Twenty-one patients (13%) were still hyperthyroid, 45 (28%) were euthyroid, 44 (28%) were subclinically hypothyroid, and 48 (30%) were overtly hypothyroid. Positive results were obtained in 10 (48%) of the 21 patients with hyperthyroidism for both TSAb and TBII assays, and in 3 patients (14%) in one of the assays. In contrast, only two (5%) patients with subclinical hypothyroidism and 1 (2%) patient with overt hypothyroidism tested positive in both assays, and 11 (25%) subclinically hypothyroid patients and 15 (31%) overtly hypothyroid patients tested positive in one of the assays. The correlation coefficients between TSAb and TBII were 0.88 (p < 0.01) in hyperthyroid patients, 0.49 (p < 0.01) in euthyroid patients, 0.34 (p < 0.05) in subclinically hypothyroid patients, and 0.12 (p > 0.05) in patients with overt hypothyroidism. Findings indicate the presence of long-term changes in the population of TSH receptor antibodies years after 131I treatment, which may influence thyroid function.

Inhibitors of anchorage-independent growth affect the growth of transformed cells on poly(2-hydroxyethyl methacrylate)-coated surfaces

We have described a microplate colorimetric assay to quantitate anchorage-independent cell growth, using plates coated with an anti-adhesive polymer poly (2-hydroxyethyl methacrylate) (polyHEMA).We investigated whether this method could be applied to human cancer cells of epithelial origin. HAG-1, a non-tumorigenic human gall-bladder carcinoma cell line, and its pSVneo and c-H-ras transfectants, which are also non-tumorigenic, did not grow on a polyHEMA-surface. In contrast, the v-src transformant which produced tumors in nude mice and formed colonies in soft agar, was able to proliferate on the coated surface, suggesting that tumorigenicity of human cancer cells correlates with the ability to grow on a polyHEMA-coated surface. We report on the feasibility of this method as a screening system for inhibitors of oncogenic transformation. Herbimycin A and radicicol, which have been reported to block Src function, suppressed the growth of v-src-transformed NRK and HAG-1 cells on the non-adhesive polyHEMA-surface at concentrations significantly lower than on plastic. Differences in the inhibitory concentrations were not observed with KB cells, and cytotoxic agents such as adriamycin did not show any selectivity between the 2 surfaces. Growth of ras-transformed cells on the coated surface was selectively blocked by L-739,749, a farnesyltransferase inhibitor. The results demonstrate that compounds causing reversion of transformed cells to normal, hence, selectively inhibiting cell growth in anchorage-independent conditions, can be screened using this microtiter plate assay.

Effects of thyroid hormone on carbonic anhydrase I concentration in human erythroid burst-forming unit-derived cells

Individuals with hyperthyroidism exhibit red blood cell concentrations of carbonic anhydrase I (CAI) that reflect the integrated serum thyroid hormone concentration over the preceding few months. Furthermore, T3, at a physiological free concentration, decreases the CAI concentration in human erythroleukemic YN-1 cells. The effect of T3 on CAI concentration in burst-forming unit-erythroid (BFU-E)- derived cells, obtained by culturing peripheral blood mononuclear cells with various cytokines, including erythropoietin, has now been investigated. BFU-E-derived cells contained a high concentration of CAI (mean +/- SE, 4.8 +/- 0.8 x 10(-12) mol/10(6) cells; n = 8). The CAI in BFU-E-derived cells was immunologically identical to that present in mature red blood cells. T3 decreased the CAI concentration in BFU-E-derived cells in a dose-dependent manner (28%, 47% and 75% decreases at 3 x 10(-10), 1 x 10(-9), and 3 x 10(-9) mol/liter T3, respectively). These results suggest that BFU-E-derived cells may be used to study the effect of T3 on human red blood cell CAI. This system may prove useful in the tissue diagnosis of resistance to thyroid hormone.

Isolation of inhibitors of TPA-induced mouse ear edema from Hoelen, Poria cocos

Triterpene carboxylic acids were isolated from the methanol extract of Hoelen, Poria cocos, and found to inhibit 12-O-tetradecanoylphorbol 13-acetate (TAP)-induced mouse ear edema. Their chemical structures were identified as 3 beta,-16 alpha-dihydroxylanosta-7,9(11),24-trien-21-oic acid, 16 alpha-hydroxydehydropachymic acid, 16 alpha-hydroxytrametenolic acid and dehydrotumulosic acid.

Effects of aspirin on status of thrombin generation in atrial fibrillation

Aspirin 330/mg/day suppressed platelet function in patients with atrial fibrillation, although it did not affect the increased coagulation activity in these patients. Findings support the premise that anticoagulant therapy is more appropriate than aspirin for the prevention of systemic embolism in patients with atrial fibrillation.

Thyroid hormone regulates rat placental type III iodothyronine deiodinase activity by inducing kinetic changes different from those in the same isozyme in rat brain

The kinetics of type III iodothyronine deiodinase (5-D) in rat placenta and brain and the role of phospholipids in enzyme activity were determined. Pregnant Sprague-Dawley rats were given either vehicle (control group) or T4 (15 micrograms/100 g bw/day; hyperthyroid group) from the 14th to the 21st day of gestation. Mitochondrial-microsomal fractions of the placenta and brain were used as the source of T4 5-D. Placental T4 5-D activity in the hyperthyroid group was increased when determined at 13 nM T4, but it was not significantly different from the control value when assayed at 1.3 microM T4. In contrast, T4 5-D in the brain was significantly increased in the hyperthyroid group regardless of the substrate concentration. Hyperthyroid rats showed decreased Km for placental 5-D and increased Vmax for brain 5-D. CM-Sephadex chromatography of solubilized placental microsomes was performed to determine whether phospholipids cause a reduction in the Km of placental 5-D in hyperthyroid rats. T3 5-D activity was undetectable unless protein-containing fractions were combined with phospholipid-containing fractions in the reaction mixture. Kinetic studies revealed that phospholipids had no effects on either Km or Vmax of placental T3 5-D. These data indicate that 5-D activity in the rat placenta is increased in hyperthyroidism with different kinetic changes from those in the brain, and that phospholipids have no effects on the kinetic parameters of placental 5-D whereas they are essential for the enzyme activity.

Intercellular adhesion molecule-1 (ICAM-1) in the sera of patients with Graves' disease: correlation with disease activity and treatment status

Intercellular adhesion molecule (ICAM-1), a ligand for lymphocyte function-associated antigen-1 (LFA-1), plays an important role in a variety of immune-mediated mechanisms such as lymphocyte attachment to cultured Graves' thyroid cells. We report the detection of a soluble form of the ICAM-1 molecule (sICAM-1) in sera from patients with Graves' disease (GD) and other thyroid disorders. The mean (+/- SD) sICAM-1 concentration in 28 euthyroid control subjects was 1931 +/- 681 pmol/L. The mean sICAM-1 concentration in 25 untreated hyperthyroid patients with GD was significantly elevated (3065 +/- 890 pmol/L), and decreased significantly (2489 +/- 845 pmol/L) after treatment with antithyroid drugs and/or 131I. Of 14 GD patients who had been in remission following administration of antithyroid drugs, 12 had recurrent disease. In 10 of the 12 patients in whom GD recurred, the sICAM-1 concentration (3807 +/- 796 pmol/L) increased significantly. The mean sICAM-1 concentration in patients with hypothyroidism due to chronic thyroiditis (n = 15:2895 +/- 569 pmol/L) was significantly elevated over that of control subjects, and not different from untreated hyperthyroid patients. The mean sICAM-1 concentration in patients with subacute thyroiditis (n = 13: 3036 +/- 441 pmol/L) was significantly elevated, while the mean sICAM-1 concentration in patients with nodular goiter (n = 10: 2318 +/- 490 pmol/L) was within the normal range. These results indicate that mean serum sICAM-1 concentration was significantly elevated in patients with untreated GD, and it decreased after treatment and increased at the time of recurrence. Therefore, the elevated serum concentration of sICAM-1 in patient with GD probably reflects ongoing immune processes.

A microplate assay for quantitation of anchorage-independent growth of transformed cells

We developed a 96-well microplate assay to quantitate anchorage-independent growth of transformed cells. Wells of tissue culture microtiter plates are coated with poly(2-hydroxyethyl methacrylate) (poly-(HEMA)) to prevent cell attachment, and cells suspended in liquid media are seeded into the treated plates. Cell growth is assessed by tetrazolium dye reduction or by counting [3H]thymidine incorporation into DNA. There appeared to be a close correlation between growth in poly(HEMA)-coated plates and colony formation in soft agar, i.e., fibroblasts transformed by various oncogene proliferated in the coated plates, whereas their normal counterparts did not. Transformed cells on the nonadhesive surface were round and formed multicellular spheroids which resembled colonies in soft agar. Cells carrying either temperature-sensitive v-src or inducible v-Ki-ras oncogene proliferated on poly(HEMA)-coated plates only when they displayed transformed phenotype. This method is simple, quick, quantitative, and economical and in many cases might be more practical than conventional soft agar colony formation assay for measurement of anchorage-independent growth.

Lack of an effect of Madopar on the disposition of tolcapone and its 3-O-methylated metabolite in rats

The effect of Madopar (benserazide and L-dopa, 1:4) on the disposition of the new selective inhibitor of catechol-O-methyltransferase, tolcapone, in rats was investigated. There was no statistically significant difference in the pharmacokinetic parameters of tolcapone in the presence or absence of Madopar except for a change in the mean residence time after oral administration. Thus, we rejected the hypothesis that the consumption of S-adenyl-L-methionine by Madopar would change the disposition of tolcapone. There were no statistically significant differences in the cumulative amount absorbed of drug and the absorption rate in the presence or absence of Madopar. We concluded that there was no interaction between tolcapone and Madopar.

Long-term effects of radioiodine on thyrotrophin receptor antibodies in Graves' disease

OBJECTIVE

Graves' disease is recognized as an organ-specific autoimmune disorder caused by the presence of TSH receptor antibodies. The long-term effects of 131I treatment for Graves' disease on TSH receptor antibodies have not previously been studied. We have measured the TSH-binding inhibitory immunoglobulin (TBII) index and thyroid stimulating antibody (TSAb) activity in patients with Graves' disease following treatment with 131I.

DESIGN

A retrospective study.

PATIENTS

Two hundred and twenty-five patients with Graves' disease who were treated with 131I 1-13 years earlier were studied (1 year: 27 patients; 2-5 years: 42 patients; 6-9 years: 79 patients; 10-13 years: 77 patients).

MEASUREMENTS

The TBII index was measured as the percentage 125I-TSH bound to pig thyroid membranes and TSAb activity as the amount of cAMP produced by cultured FRTL-5 cells.

RESULTS

TBII was detected in 78% of patients prior to 131I administration. Following 131I administration, the incidence of positive TBII was 85% at the end of the first year decreasing to 40, 19, and 17% at 2-5, 6-9 and 10-13 years, respectively. The frequency of a positive TSAb was 74% at the end of the first year, and also decreased to 49, 27 and 29% at 2-5, 6-9 and 10-13 years, respectively. At more than 2 years after 131I therapy, the frequencies of hyperthyroidism in TBII and TSAb positive patients were 42% (19/45) and 30% (19/63), respectively, which were significantly higher than those in TBII and TSAb negative patients (8%: 12/153 and 8%:11/131, respectively). The frequency of hyperthyroidism after 131I treatment in patients with negative TBII before treatment (7%:2/29) was significantly lower than that (29%:30/102) in patients with positive TBII before treatment.

CONCLUSIONS

These results indicate that (1) the TBII index and TSAb activity decreased over a period of more than 2 years after 131I therapy for Graves' disease, and (2) the TBII index before treatment may influence the long-term outcome of 131I therapy.

Enhanced plasma GH responses to simultaneous administration of TRH and GHRH in patients with primary hypothyroidism

The mechanism of aberrant GH responses to TRH was indirectly evaluated in 7 patients with primary hypothyroidism. All patients showed GH response to TRH. When TRH was administered together with GHRH, the plasma GH response was much greater than after a single administration of TRH or GHRH (TRH+GHRH vs. TRH or GHRH: max. delta GH, 16.4 +/- 3.2 vs. 5.4 +/- 1.3 or 6.0 +/- 0.8 microgram/L; AUC, 1282.7 +/- 234.7 vs. 384.0 +/- 95.0 or 441.8 +/- 66.2, both P < 0.01). The combined administration of TRH and GHRH caused an additive, but not a synergistic, GH response. In contrast, 8 normal subjects showed neither any plasma GH response to TRH nor enhancement by TRH of GHRH-induced GH response following combined administration. It is concluded that the sites of action of TRH seemed to be different from GHRH in patients with primary hypothyroidism.

Conversion of epidermal growth factor (EGF) into a stimulatory ligand for A431-cell growth by herbimycin A by decreasing the level of expression of EGF receptor

We examined effect of the tyrosine kinase inhibitor herbimycin A on A431 human epidermoid carcinoma cells which over-express epidermal growth factor (EGF) receptor. Herbimycin A inhibited the autophosphorylation of EGF-stimulated receptors in intact cells both time- and dose-dependently. The inhibition was found to be due to a decrease in the level of expression of the receptor amount, because herbimycin A equally decreased the receptor quantity and EGF-stimulated receptor kinase activity in intact cells, but did not exhibit a direct inhibitory effect on EGF receptor kinase activity in vitro. The decrease of the level of EGF receptor was also confirmed by 125I-EGF binding to herbimycin A-treated cells, and Scatchard analysis showed that the decrease in the receptor number occurred in the major population of the low-affinity binding ones, whereas the number with high-affinity binding was unaffected. Interestingly, although the proliferation of A431 cells was inhibited by EGF, herbimycin A converted EGF into a stimulatory ligand for cell growth, as determined by both cell number and DNA synthesis. These findings indicated that herbimycin A decreased the level of expression of EGF receptor by a mechanism other than inactivation of the receptor kinase and reversed the transformed phenotype of A431 cells to a normal one in the proliferative response to EGF.

Effects of thyroid hormone on carbonic anhydrase I levels in human erythroid (YN-1) cells

We recently have reported that patients with hyperthyroidism have red blood cell carbonic anhydrase I (CAI) levels that reflect the patient's integrated thyroid hormone level over the preceding few months. In the present study, the effect of T3 on CAI concentrations in the human erythroleukemic cell line, YN-1, was studied. The presence of high affinity (1.9 x 10(9) L/mol), low capacity (20.4 fmol/10(6) cells) T3 binding sites was demonstrated in YN-1 cell nuclei. T3 at a physiological free T3 concentration (0.54 nmol/L) significantly (32 +/- 7%, P < 0.01) decreased CAI concentrations in YN-1 cells before induction of differentiation. The effect of T3 on CAI levels was more obvious (42 +/- 7%, P < 0.01) in the presence of transforming growth factor-beta 1 (TGF-beta 1), which induces hemoglobin synthesis and differentiation in YN-1 cells. These results suggest that the YN-1 cell line may be used to study T3 action on human red blood cell CAI.