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E Ogata
Publications and source records attributed to E Ogata.
[Role of thyroid hormones in sugar metabolism system].
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1,25-Dihydroxyvitamin D3 inhibits synthesis and enhances degradation of proteoglycans in osteoblastic cells.
The effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), an active form of vitamin D3, on the metabolism of proteoglycans by an osteoblastic cell line MC3T3-E1 were studied. Cells metabolically labeled with [35S]sulfate and/or [3H]glucosamine synthesized large and small dermatan sulfate proteoglycans and heparan sulfate proteoglycan. The incorporation of [35S]sulfate into proteoglycans for 1 h was reduced by 1,25-(OH)2D3 in a dose-dependent manner with a maximum reduction of 40% obtained at 10(-8)M 1,25-(OH)2D3. This effect was observed for all the proteoglycans with the decrease for the large dermatan sulfate proteoglycan most prominent. Treatment with 1,25-(OH)2D3 did not influence the degree of sulfation nor the molecular size of the glycosaminoglycan chains. Thus, the change in the incorporation of [35S] sulfate reflects net change in the synthesis of proteoglycans. When cells were treated with beta-D-xyloside, 1,25-(OH)2D3 also inhibited net synthesis of dermatan sulfate glycosaminoglycan chains on this exogenous substrate suggesting that it decreases the capacity of the cells for glycosaminoglycan synthesis. The incorporation of [3H]glucosamine into hyaluronic acid was also inhibited up to 70% by 10(-8) M 1,25-(OH)2D3. Treatment with 24,25-dihydroxyvitamin D3 did not cause significant changes in the proteoglycan synthesis. Degradation of proteoglycans associated with the cell layer was enhanced by treatment with 1,25-(OH)2D3 at 10(-8) M. Proteoglycans exogenously added to the culture were also degraded with a cell-mediated process which was stimulated by treatment with 10(-8) M 1,25-(OH)2D3. These results demonstrate that 1,25-(OH)2D3 reduces the synthesis and stimulates the degradation of proteoglycans in osteoblastic cells in culture.
Existence of parathyroid hormone binding sites on murine hemopoietic blast cells.
We demonstrated that 125I-labeled human parathyroid hormone (1-34;8,18-Nle,34-Tyr)[[125I]hPTH(1-34)] bound specifically to hemopoietic blast cells supported by granulocyte-macrophage colony-stimulating factor. Half-maximal inhibition of binding was achieved at concentrations of unlabeled hPTH(1-34) of about 5 x 10(-9)M. Insulin and hPTH(39-68) did not compete for PTH binding sites. Specific binding of hPTH(1-34) was detected in neither macrophages nor multinucleated cells (MNC's). Furthermore, treatment of hemopoietic blast cells with hPTH(1-34) stimulated MNC formation, and the range of concentrations (10(-10)-10(-8)M) over which hPTH(1-34) caused these effects was similar to that which inhibited the binding of [125I]hPTH(1-34). These findings suggest the presence of a PTH receptor on osteoclast precursors and the direct effect of PTH on them, resulting in osteoclast-mediated bone resorption.
Platelet-derived growth factor stimulates synthesis of 1,2-diacylglycerol from monoacylglycerol in Balb/c 3T3 cells.
1,2-Diacylglycerol (1,2,-DAG) plays an important role in the protein kinase C-mediated signal-transduction system. Several reports have shown that 1,2-DAG is generated through various pathways other than classical phospholipid hydrolysis. We observed a rapid incorporation of [3H]myristate into 1,2-DAG in platelet-derived-growth-factor (PDGF)-treated Balb/c 3T3 cells. [14C]Palmitate was similarly incorporated into 1,2-DAG. The effect of PDGF, which was inhibited by cycloheximide, became maximal after 60 min treatment with PDGF, and disappeared 300 min after removal of PDGF. Treatment with triacylglycerol lipase revealed that labelled saturated fatty acid was incorporated into the sn-1 position. PDGF barely stimulated incorporation of [3H]glycerol or [14C]glucose into 1,2-DAG. Incorporation of [3H]myristate into 1,2-DAG preceded that into triacyglycerol and phospholipids. These results suggest that synthesis of 1,2-DAG from monoacylglycerol is enhanced in PDGF-treated cells. However, there is no significant difference in the activity of monoacylglycerol acyltransferase measured in vitro in quiescent and PDGF-treated cells. The reason for this discrepancy is discussed.
Parathyroid hormone-related protein in adult T-cell leukemia-lymphoma.
OBJECTIVE: To determine whether parathyroid hormone-related protein is synthesized and secreted by the tumor cells of patients with adult T-cell leukemia-lymphoma. DESIGN AND PATIENTS: Convenience sample of three patients with adult T-cell leukemia-lymphoma. Two patients developed hypercalcemia, and one patient was normocalcemic. SETTING: Inpatient facilities at two university-affiliated medical centers. INTERVENTION: All patients had a lymph node biopsy. In addition, samples of ascitic or pleural fluid, or both, were obtained from these patients. MEASUREMENTS AND RESULTS: Using RNA blot analysis, we showed that parathyroid hormone-related protein (PTHrP) messenger RNAs (mRNAs) were constitutively expressed in the tumor cells from all patients. Cyclic adenosine monophosphate (cAMP) production-stimulating activity, assessed using osteoblast-like UMR106 cells, was demonstrated in the pleural and ascitic fluids from the two patients who developed hypercalcemia. The elution profiles of the cAMP production-stimulating activity in the ascitic fluid extracts were very similar to those of the tumor extracts from hypercalcemic nude rats that had been implanted with a human cancer tumor. CONCLUSIONS: Parathyroid hormone-related protein is produced by tumor cells in adult T-cell leukemia-lymphoma, which may be an important factor in the development of hypercalcemia in the patients with this disease. However, the development of hypercalcemia may depend on other factors such as the number of tumor cells, access of the protein into systemic circulation, and the presence of some additional substances.
Possible direct linkage of insulin-like growth factor-II receptor with guanine nucleotide-binding proteins.
In mouse Balb/c3T3 fibroblasts, insulin-like growth factor (IGF)-II activates a calcium-permeable cation channel through a cell surface IGF-II receptor (Kojima, I., Nishimoto, I., Iiri, T., Ogata, E., and Rosenfeld, R. G. (1988) Biochem. Biophys. Res. Commun. 154, 9-19; Matsunaga, H., Nishimoto, I., Kojima, I., Yamashita, N., Kurokawa, K., and Ogata, E. (1988) Am. J. Physiol. 255, C442-C446). In the action of IGF-II, a pertussis toxin (or islet-activating protein; IAP)-sensitive GTP-binding protein (G protein) is inferred to be involved (Nishimoto, I., Hata, Y., Ogata, E., and Kojima, I. (1987) J. Biol. Chem. 262, 12120-12126). In the present study, we examined the direct coupling of the IGF-II receptor with G proteins. In broken Balb/c3T3 cell membranes, 10 nM IGF-II rapidly attenuated the IAP-catalyzed ADP-ribosylation of a 40-kDa protein in a manner requiring magnesium ion. The IGF-II-mediated attenuation in the IAP substrate activity was 80% recovered after washing off IGF-II and inhibited by coexisting guanosine 5'-O-(2-thiodiphosphate), while either aluminum fluoride solution (10 mM NaF plus 100 microM AlCl3) or 100 microM guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) reproduced the action of IGF-II. When purified IAP substrate G proteins (Gi1, Gi2, G0) were incubated with IGF-II in the presence of membranes from IAP-treated Balb/c3T3 cells, the attenuation in the IAP substrate activity was evident in Gi2, but not in Gi1 or G0. On the other hand, 10 nM insulin had no effect on the modification of the 40-kDa IAP substrate in Balb/c3T3 cell membranes, whereas 10 nM IGF-I elicited a slow onset of the IAP sensitivity attenuation from the 40-kDa protein. However, the specific involvement of the IGF-II receptor in the modification of the IAP substrate induced by low concentrations of IGF-II was suggested by the observations that (i) IGF-I receptor-lacking cell membranes were effective for the Gi2 modification by IGF-II, (ii) the ability of membranes to mediate the action of IGF-II was markedly attenuated in IGF-II receptor-lacking cell membranes, and (iii) agonistic anti-IGF-II receptor antibody mimicked the action of IGF-II on the 40-kDa protein in Balb/c3T3 cell membranes in a dose-dependent manner similar to that observed in the antibody-induced blocking of membrane IGF-II binding.(ABSTRACT TRUNCATED AT 400 WORDS)
[Clinical studies using a highly sensitive radioimmunoassay for mid-region and carboxy terminus of parathyroid hormone in normal, hypo- and hypercalcemic states].
Parathyroid hormone radioimmunoassay (RIA), specific for mid-region of the PTH molecule, has been proven to be extremely useful for the differential diagnosis of abnormal calcium metabolism. Recently, we developed a highly sensitive RIA for PTH, consisting of PTH antiserum (CH9), 125I labelled Tyr42 hPTH (43-68) and synthetic hPTH (1-84) as standard. This RIA cross-reacted with mid-region and carboxyl terminals of PTH. The within-assay and between-assay coefficients of variation were less than 4.6% and less than 8.6%, respectively. The limit of detection was 50pg/ml. The levels of serum calcium, serum phosphate, serum creatinine, Tmpo4/GFR and creatinine clearance (Ccr) in normal healthy volunteers aged 20 to 50 years remained almost constant and showed 9.24 +/- 0.34mg/dl (mean +/- SD, n = 242), 3.34 +/- 0.38mg/dl (n = 242), 0.870 +/- 0.121mg/dl (n = 242), 3.20 +/- 0.54mg/dl GF (n = 189) and 103 +/- 17ml/min (n = 137), respectively. All healthy volunteers (n = 326) had measurements of PTH in the blood. From 20 to 50 years, normal PTH mean was 374 +/- 97pg/ml (+/- SD, n = 237) and ranged from 180-568pg/ml, and from 60 to 80 years it was 471 +/- 133pg/ml (n = 34) and ranged from 205-737pg/ml. Since we found that PTH was markedly elevated above normal when Ccr was below 40ml/min, and PTH was very significantly correlated with the reciprocal of Ccr (r = 0.8996, P less than 0.001) using a multivariate analysis, all of the patients whose Ccr was higher than 40ml/min were selected and examined in the following studies. Serum PTH values completely separated patients with surgically proven primary hyperparathyroidism (1 degree HPT) from malignant associated hypercalcemia (MAH), and patients with idiopathic hypoparathyroidism (IHP) from pseudohypoparathyroidism (PHP), both of which were diagnosed by Ellsworth-Howard test. PTH values in all of the patients with 1 degree HPT (n = 23) were above normal, but those with MAH (n = 6) were below the normal or lower normal range. PTH values in patients with PHP (n = 7) showed above normal, while those with IHP (n = 5) were below the normal range. PTH was normalized in post operative status in all patients after parathyroidectomy (n = 6). These results indicate that this PTH RIA is extremely useful for the differential diagnosis in diseases with calcium abnormalities.
A stimulatory effect of somatostatin: enhancement of activin A-mediated FSH secretion in rat pituitary cells.
The interaction between somatostatin and activin A was studied in terms of FSH secretion in rat pituitary cells in primary culture. Incubation of pituitary cells with 1 nM activin A for 48 hrs resulted in an increase in FSH release into incubation medium. The effect of activin A was dependent on cell-density and the higher the density, the smaller the stimulatory action of activin A. Somatostatin, by itself, did not affect the FSH secretion. When 100 nM somatostatin was included together with activin A or the cells were pretreated with somatostatin for 2 hrs, the activin A-induced FSH secretion was enhanced. This potentiation effect of somatostatin was inversely dependent on the cell-density. These results indicate that somatostatin enhances, rather than inhibits, the activin A action in pituitary cells.
Secretion of parathyroid hormone-like activity from human T-cell lymphotropic virus type I-infected lymphocytes.
Because many patients with adult T-cell leukemia/lymphoma (ATLL) develop hypercalcemia with similar characteristics to those of humoral hypercalcemia of malignancy (HHM) (Arch. Intern. Med., 148: 921-925, 1988), we investigated if ATLL cells produce parathyroid hormone (PTH)-like activity. Conditioned media from cultures of human T-cell lymphotropic virus type I-infected cell line (MT-2) as well as peripheral lymphocytes from a hypercalcemic ATLL patient stimulated cyclic AMP production in osteoblast-like rat osteogenic sarcoma cells (UMR 106) and bone resportion in organ cultures of fetal mouse calvaria. Furthermore, the stimulation of cyclic AMP production by conditioned medium of MT-2 cells was inhibited by human PTH(3-34), indicating that MT-2 cells secrete PTH-like activity. The PTH-like activity from MT-2 cells was chromatographically indistinguishable from the one extracted from a solid tumor causing HHM. The present results along with our previous observation that MT-2 cells constitutively express mRNA for PTH-related protein (Biochem. Biophys. Res. Commun., 154: 1182-1188, 1988) demonstrate that a PTH-like activity is synthesized and secreted by these cells, and are consistent with the hypothesis that elaboration of PTH-like activity by ATLL cells may be the mechanism by which hypercalcemia develops in ATLL patients as well as in solid cancer patients with HHM. However, these results do not rule out the possibility that other factors such as interleukin 1 are also involved and may act in concert with PTH-like activity in the development of hypercalcemia in ATLL.
Dual effect of activin A on cell growth in Balb/c 3T3 cells.
Effects of activin A on cell growth were studied in Balb/c 3T3 cells. When incubated with serum, activin A inhibited serum-induced increase in DNA synthesis in a concentration-dependent manner. Activin A also inhibited serum-induced increase in cell number. When added in quiescent cells, activin A did not affect competence-inducing activity of PDGF. Activin A by itself had a small competence-inducing activity. In contrast, when added in competent cells, activin A inhibited progression activity of platelet-poor plasma. These results indicate that activin A has dual action on cell proliferation in Balb/c 3T3 cells.
Calcium rather than cyclic AMP is an intracellular messenger of parathyroid hormone action on glycogen metabolism in isolated rat hepatocytes.
The synthetic 1-34 fragment of human parathyroid hormone (1-34hPTH) stimulated glucose production in isolated rat hepatocytes. The effect of 1-34hPTH was dose-dependent and 10(10) M-1-34 hPTH elicited the maximum glucose output, which was approx. 80% of that by glucagon. Although 1-34hPTH induced a small increase in cyclic AMP production at concentrations higher than 10(-9) M, 10(-10) M-1-34hPTH induced the maximum glucose output without significant elevation of cyclic AMP. This is in contrast to the action of forskolin, which increased glucose output to the same extent as 10(-10) M-1-34hPTH by causing a 2-fold elevation of cyclic AMP. In addition to increasing cyclic AMP, 1-34hPTH caused an increase in cytoplasmic free calcium concentration ([Ca2+]c). When the effect of 1-34hPTH on [Ca2+]c was studied in aequorin-loaded cells, low concentrations of 1-34hPTH increased [Ca2+]c: the 1-34hPTH effect on [Ca2+]c was detected at as low as 10(-12) M and increased in a dose-dependent manner. 1-34hPTH increased [Ca2+]c even in the presence of 1 microM extracellular calcium, suggesting that PTH mobilizes calcium from an intracellular pool. In line with these observations, 1-34hPTH increased the production of inositol trisphosphate. These results suggest that: (1) PTH activates both cyclic AMP and calcium messenger systems and (2) PTH stimulates glycogenolysis mainly via the calcium messenger system.
Na-Ca exchanger as a calcium influx pathway in adrenal glomerulosa cells.
When aequorin-loaded glomerulosa cells were incubated in isotonic Na2+-free medium containing N-methyl-D-glucamine instead of NaCl, there was an increase in cytoplasmic free calcium concentration, [Ca2+] c, which was not observed when extracellular calcium concentration was reduced to 1 microM. Upon removal of extracellular sodium, there was nearly five-fold increase in fractional efflux ratio of calcium. The reduction of extracellular sodium resulted in a stimulation of calcium influx rate, the magnitude of which was dependent on extracellular sodium concentration. Similar stimulation of calcium influx was observed when extracellular sodium was replaced with lithium. Nitrendipine did not affect the calcium influx induced by the reduction of extracellular sodium while a derivative of amiloride 3',4'-dichlorobenzamil, which inhibits Na-Ca exchange, attenuated calcium influx observed in sodium-free medium. These results indicate that removal of extracellular sodium leads to an increase in [Ca2+] c by stimulating calcium influx and that calcium enters the cell via Na-Ca exchanger.
Stimulation of insulin secretion by transforming growth factor-beta.
Effects of transforming growth factor-beta (TGF-beta) on insulin secretion were studied in rat pancreatic islets. When islets were incubated in a batch incubation system with various concentrations of TGF-beta in the presence of 2.8 mM glucose, TGF- beta increased insulin release in a concentration-dependent manner. Both TGF- beta 1 and TGF- beta 2 were equally effective. The stimulatory action of TGF- beta was greater in the presence of stimulatory concentration of glucose. In perifusion system, TGF- beta induced an immediate monotonic increase in insulin secretion. These results indicate that TGF- beta is a stimulator of insulin secretion.
Increased sympathoadrenomedullary activity and left ventricular hypertrophy in young patients with borderline hypertension.
Echocardiographic dimensions and endocrinological examination were performed in 71 young patients with borderline hypertension (BHT) and 31 age-matched normotensive subjects (NT). Patients with BHT had significantly higher relative wall thickness (RWT) and left ventricular mass index than NT, although all BHT patients showed no asymmetric increase in the ratio of septal to posterior wall thickness. Moreover, these BHT patients demonstrated an increased cardiac output and an augmented mean circumferential fiber shortening rate (mean Vcf), suggesting left ventricular hyperfunction. Overall, there was a positive correlation between RWT and mean Vcf in BHT patients (r = 0.700, P less than 0.001), although there was no significant relationship between RWT and blood pressure. Furthermore, these BHT patients had higher plasma epinephrine (PE) and plasma renin activity compared to NT, suggesting the increased sympathoadrenomedullary activity in BHT. These BHT patients were divided into two groups with regards to PE levels; namely a high PE group (PE greater than or equal to 46 pg/ml) and a normal PE group (PE less than 46 pg/ml). The high PE group had a significantly higher mean Vcf and RWT than the normal PE group. These findings suggest that in young BHT patients left ventricular hypertrophy could be related to abnormalities of the sympathoadrenomedullary systems.
Human PTH(1-34) infusion test in differential diagnosis of various types of hypoparathyroidism: an attempt to establish a standard clinical test.
To introduce a simple procedure and reliable diagnostic criteria for parathyroid hormone (PTH) infusion test, 128 patients with either pseudo- (PsH) or idiopathic hypoparathyroidism (IdH) and 25 normocalcemic controls were studied. Incremental responses of urinary cyclic AMP and phosphate to 20 micrograms (67 U) or 30 micrograms (100 U) of human PTH(1-34) were assessed by using simple parameters of urinary excretion rates of the two substances. The results are summarized as follows. (1) PTH dose-cyclic AMP response relation suggests that 100 U of PTH is more appropriate than 67 U as a standard test dose for adults. (2) By presenting the magnitude of cyclic AMP response as either net increase or fold increase during 1 h after 100 U of PTH infusion, we can differentiate PsH type I from others without overlap. (3) Differentiation between PsH and IdH or normocalcemic subjects by phosphaturic response is less clearcut than that made by cyclic AMP response whatever indices and criteria are used. Thus it seems difficult to diagnose PsH type II merely based on the discrepancy between cyclic AMP and phosphaturic responses to exogenous PTH. (4) The test results are essentially similar in the examinations performed before and during vitamin D therapy. However, when the magnitude of phosphaturic response is expressed as net increase during 2 h after PTH, it tends to be enhanced after vitamin D therapy in patients with PsH compared to the response before therapy.
Hypocalcemia increases and hypercalcemia decreases the steady-state level of parathyroid hormone messenger RNA in the rat.
To examine the effects of serum calcium concentrations on PTH biosynthesis, rats were made hyper- (serum total calcium, approximately 3.5 mM) or hypocalcemic (approximately 1.25 mM) and steady-state levels of PTH mRNA in parathyroid cells were measured by the primer extension method using a 32P-labeled synthetic oligomer. PTH mRNA levels increased about twofold in the rats made slightly hypocalcemic by infusion of calcium-free solution and decreased slightly in those made hypercalcemic by CaCl2 infusion (120-150 mumol/h) compared with the levels present in nonfasting control rats. Infusion of calcitonin (0.5 U/h) or EGTA (90 mumol/h) with calcium-free solution increased PTH mRNA levels further (two- to sevenfold) above the levels present in animals infused with calcium-free solution alone. These changes in PTH mRNA levels were observed after 48- but not 24-h infusion, and there was an inverse correlation between PTH mRNA levels and serum calcium concentrations. The results suggest that changes in serum calcium concentrations in the near physiological range regulate the biosynthesis of PTH by affecting steady-state levels of PTH mRNA when hypercalcemia or hypocalcemia continues for a relatively long period.
Ambient C1- ions modify rat mesangial cell contraction by modulating cell inositol trisphosphate and Ca2+ via enhanced prostaglandin E2.
Our recent observation showed that angiotensin II (AII) and arginine vasopressin (AVP) stimulate Ca2+-activated Cl- conductance in mesangial cells. These data raise the possibility that mesangial cell function may be modulated by extracellular chloride concentration [( Cl-]o). The present study was undertaken to test this possibility using cultured rat mesangial cells. When the [Cl-]o was reduced to zero, the percentage of mesangial cells showing contraction responding to AII and AVP was decreased from 72 +/- 9 to 33 +/- 10% and from 60 +/- 4 to 24 +/- 11%, respectively. Ca2+ transients induced by AII and AVP, measured in mesangial cells loaded with Ca2+-sensitive photoprotein aequorin, were attenuated as [Cl-]o decreased. Also, when [Cl-]o decreased, inositol trisphosphate (IP3) levels of mesangial cells were suppressed, both in the presence and absence of AII or AVP. PGE2 production by mesangial cells increased when [Cl-]o decreased and the effects of ambient Cl- deprivation could be restored by addition of indomethacin to the Cl- -free medium. Moreover, PGE2 decreased mesangial cell contractility, Ca2+ transients, and IP3 production in response to AII and AVP. These data suggest that the decrease in [Cl-]o attenuates mesangial cell contraction by suppressing IP3 production and thus Ca2+ transients in response to AII and AVP through enhanced PGE2 production.