The synthesis of metallothionein-like protein containing zinc in liver of rat after administration of calcium and calcitonin

Subcutaneous (s.c.) and intraperitoneal (i.p.) injection and oral administration of calcium (Ca) into rats increased Ca content of liver compared with control rats. When liver cytosol was filtered through a Sephadex G-75 column, zinc (Zn) content of metallothionein (MT)-like protein fraction was several times higher in Ca treatment than in control. Zn and copper (Cu) content of high-molecular (HM) and moderate-molecular (MM) fractions and Cu content of MT fraction was unaffected by Ca treatment. Zn in MT fraction showed two peaks in the direct-connection method of high-performance liquid chromatography to atomic absorption spectrophotometer (AAS). The retention time of these two peaks agreed with those of Zn or cadmium (Cd) in MT fraction of liver cytosol obtained from Zn- or Cd-administered rat. These results show that MT-like protein containing Zn is induced by Ca. In conditions showing a slight increase in liver Ca and a significant decrease in serum Ca by synthetic [Asu1,7] eel calcitonin (CT) injection, gel filtration of liver cytosol obtained from CT-treated rats showed a higher content of Zn and a higher radioactivity of [3H]cystine than that from control injection. This suggests that CT causes an increase in liver Ca and results in induction of MT-like protein containing Zn by Ca.

Human parathyroid hormone inhibits renal 24-hydroxylase activity of 25-hydroxyvitamin D3 by a mechanism involving adenosine 3',5'-monophosphate in rats

The in vivo effect of PTH on renal 24-hydroxylase activity of 25-hydroxyvitamin D3 (25OHD3) was examined in vitamin D-deficient thyroparathyroidectomized rats by a recently developed sensitive in vitro assay of 25OHD3-hydroxylases using rat kidney homogenates and by an in vivo assay measuring the accumulation of tritiated metabolites in plasma 5 h after injection of 25OH[3H]D3. Infusion for 20 h of either human PTH-(1-34) (except at 800 pmol/h) or cAMP did not significantly change the plasma levels of calcium and phosphorus compared with those in thyroparathyroidectomized rats given 125 ng 1,25-dihydroxyvitamin D3 to induce renal 24-hydroxylase activity. On the other hand, human PTH-(1-34) markedly inhibited renal 24-hydroxylase activity and stimulated 1-hydroxylase activity. The effective concentration of human PTH-(1-34) was much lower for inhibiting 24-hydroxylase than for stimulating 1-hydroxylase activity. Infusion of less than 100 nmol/h cAMP similarly inhibited 24-hydroxylase activity without enhancing 1-hydroxylase activity. Either theophylline (1.0 mumol/h) or a submaximal dose (25 pmol/h) of human PTH-(1-34) alone inhibited 24-hydroxylase activity only slightly, but the concomitant infusion of both chemicals markedly inhibited 24-hydroxylase activity without stimulating 1-hydroxylase activity. These effects of human PTH-(1-34) and cAMP occurred similarly in both the in vitro and the in vivo assays. The present study clearly indicates that besides its well known action in stimulating 1-hydroxylase activity, PTH inhibits renal 25OHD3-24-hydroxylase activity by a mechanism involving cAMP.

Lp(a) lipoprotein as a risk factor for coronary heart disease and cerebral infarction

Attempts were made to prepare antisera monospecific for Lp(a) lipoprotein and to investigate the distribution of subjects according to plasma levels of Lp(a) in Japanese controls and patients with coronary heart disease or cerebral infarction. Positive plasma reactions to the double diffusion test for Lp(a) (Ouchterlony) were observed in 32.3% of the healthy Japanese subjects, which is similar to results previously reported in western countries. The plasma threshold level of 17 mg/dl was considered an appropriate point for dividing subjects into positive and negative groups depending on reactions to the double diffusion test. When subjects were divided into two groups at 17 mg/dl, a significant association was found between a high plasma level of Lp(a) and either coronary heart disease or cerebral infarction in the distribution of the cortical artery. These results suggest that Lp(a) may play an important part as a risk factor for coronary heart disease and cerebral infarction.

Characterization of plasma lipoproteins in survivors of cerebral infarction

To characterize the plasma lipoproteins in survivors of cerebral infarction, plasma lipoproteins were ultracentrifugally fractionated into VLDL, LDL, HDL2 and HDL3, and the concentrations of cholesterol, phospholipid, apolipoprotein and triglyceride in each lipoprotein class were determined. Subjects examined were 15 male healthy controls and 15 male survivors of cerebral infarction situated in the distribution of cerebral cortical artery. The concentrations of VLDL-cholesterol and VLDL-triglyceride and the percent content of VLDL-cholesterol were higher in survivors than in controls. The concentration of LDL-triglyceride was higher and the percent content of LDL-cholesterol was lower in survivors than in controls. While the plasma concentration of triglyceride was higher in survivors than in controls, those of HDL, HDL2 and HDL3 were lower in survivors. The concentrations of cholesterol, phospholipid and apolipoprotein in either HDL2 or HDL3 were also reduced in survivors as compared with controls. In either HDL2 or HDL3, the percent content of triglyceride was higher and that of phospholipid was lower in survivors than in controls. These results were in good agreement with those reported for survivors of myocardial infarction, suggesting that the underlying derangement in lipoprotein metabolism is common to myocardial and cerebral infarction.

[Clinical study on unmodified intravenous dried ion-exchange resin treated human normal immunoglobulin, SM-4300]

Unmodified intravenous dried ion-exchange resin treated human normal immunoglobulin, SM-4300, was administered to 4 patients with severely intractable infectious diseases. Obvious antipyretic effect, opsonic effect and and investigational findings on healing are not observed. However, in both subjective and objective clinical effects, we obtained the following test results, that is, 1 case of effective and 2 cases of rather effective. No side effects by SM-4300 were observed.

Reduction of 2,4-dinitrotoluene by Wistar rat liver microsomal and cytosol fractions

2,4-Dinitrotoluene (2,4-DNT) is an important industrial nitroaromatic compound. 2,4-Diaminotoluene (2,4-DAT), one of the urinary metabolites of 2,4-DNT, is carcinogenic when fed to rats. The objectives of these studies were to determine whether 2,4-DAT was formed from 2,4-DNT in rat liver and to clarify the nature of enzymes responsible for reduction of 2,4-DNT to 2,4-DAT. Data obtained from thin-layer and high-pressure liquid chromatography indicated that metabolites produced by microsomal preparations were 2-amino-4-nitrotoluene (2A4NT) and its isomer (4A2NT). This microsomal activity is probably mediated by cytochrome P-450 because the reduction is blocked by carbon monoxide and primary amines [aniline, n-octylamine, and 2,4-dichloro-6-phenylphenoxyethylamine (DPEA)]. In contrast, 2,4-DNT was metabolized via 2A4NT and 4A2NT to 2,4-DAT by cytosolic preparations. The greatest part of the reduction activity was due to cytosolic xanthine oxidase because the reduction was blocked by allopurinol. The results of this investigation suggest that reduction of 2,4-DNT to 2,4-DAT by cytosolic xanthine oxidase may play a role in 2,4-DNT hepatocarcinogenicity.

Interaction between cadmium and copper in relation to the collagen metabolism of embryonic chick bone in tissue culture

To investigate the interaction between Cd and Cu in relation to the content of collagen in bone, femurs obtained from 9-day-old chick embryos were cultivated with a combination of Cd and Cu concentrations of 8.9 microM and below for 4 days. When 2.23 or 4.45 microM Cd was added to the medium containing 4.45 or 8.90 microM Cu, the presence of both Cd and Cu caused a remarkable decrease in collagen synthesis compared with a decrease in collagen synthesis caused by either Cd or Cu alone. The results show that Cd and Cu caused an interactive inhibition of collagen synthesis, which was not due to an increase in collagen degradation by Cd and Cu. At concentrations showing inhibition, Cd caused an increase in Cu content and Cu caused an increase in Cd content. The increase in Cd content was mainly caused by the accumulation of Cd in bone mineral. The increase in Cu content was due to binding to metallothionein-like protein in the cytosol induced by Cd. The relationship between inhibition and the increase in both Cd and Cu was not confirmed after division of the bone into diaphysis and epiphysis. The present study showed that Cu aggravated the bone matrix damage caused by Cd.

The effect of cadmium on the collagen solubility of embryonic chick bone in tissue culture

The effect of cadmium (Cd) on the solubility of bone collagen was examined in cultured tibiae from 9-day chick embryos. The solubility of collagen was not significantly increased by 8.9 microM Cd, but showed a significant increase at 13.4 microM Cd. As the [3H]hydroxyproline (Hyp) formation was inhibited by Cd at 8.9 and 13.4 microM [3H]Hyp formation and collagen solubility were investigated in the presence of 200 microM Fe2+, a metal which is known to prevent the inhibitory effects of Cd on prolyl hydroxylase in vitro. Fe affected neither a decrease in [3H]Hyp formation nor an increase in collagen solubility caused by Cd. This suggests that a Cd-induced increase in collagen solubility may be due to the decrease of lysyl oxidase activity, not to the formation of underhydroxylated collagen. Zn at 48 and 134 microM depressed the Cd-induced increase in collagen solubility, but caused no increase in collagen solubility. Our present and previous results suggest that Zn can protect the disturbance of both the collagen synthesis and the collagen cross linking caused by Cd.

The effect of aluminum on the metabolism of embryonic chick bone in tissue culture

The effect of aluminum (Al) on bone metabolism was assessed in organ cultures of embryonic chick bone. Al of 10(-4)M and above caused an inhibitory effect on mineralization without inhibiting matrix formation and a stimulative effect on demineralization without stimulating matrix degradation. Therefore, Al was shown to influence the mineral metabolism of bone.