Takio Hayashi

The Effects of Streptozotocin Diabetes on Hepatic Triglyceride Lipase Activity in the Rat

The function of the hepatic triglyceride lipase (H-TGL) is not yet clear. The purpose of the present study was to investigate the possible hormonal regulation of H-TGL. Postheparin plasma was obtained 3 min after the intravenous injection of 50 U/250 g body weight of heparin into male Wistar rats. The lipase activities were measured using substrate containing [14C] triolein emulsified with gum arabic and were expressed in mumoles of free fatty acid released/ml/hour (mean +/- SD). H-TGL was the lipase activity remaining after inhibition of lipoprotein lipase (LPL) by 1.0 M NaCl. Diabetic rats were prepared by intravenous injection of streptozotocin (STZ), 65 mg/kg body weight. The contributions of H-TGL and LPL to the total plasma triacylglycerol hydrolase (TGH) activity depend on the amount of heparin injected and the time of blood withdrawal after heparin injection. H-TGL was maximally released at higher heparin (50 U/250 g body weight) concentrations, compared to LPL which was maximally released at lower heparin (5 U/250 g body weight) concentrations. H-TGL was significantly higher at 3 min after the injection of 50 U of heparin/250 g body weight than at 20 min. Twenty-four-hour fasting produced a significant fall in H-TGL compared to H-TGL in fed rats. Total TGH was significantly lower in diabetic rats 3 days after STZ injection. In diabetic rats 3, 5, and 7 days after STZ injection, H-TGL were significantly lower than those in control rats. H-TGL and H-TGL/total TGH were 9.49 +/- 0.99 and 0.551 +/- 0.071, respectively, in rats 3 days after STZ injection, compared to H-TGL (13.46 +/- 0.69) and H-TGL/total TGH (0.739 +/- 0.052) in control nondiabetic rats. When diabetic rats were treated with insulin, total TGH (14.37 +/- 3.01) and H-TGL (6.77 +/- 4.12) rose to 25.16 +/- 1.02 (total TGH) and 16.49 +/- 1.13 (H-TGL), that were comparable to activities in control nondiabetic rats. Separation of H-TGL and LPL was performed using heparin-Sepharose affinity chromatography of postheparin plasma. The enzyme activity of peak I from STZ rats, which is eluted by 0.72 M NaCl-Veronal buffer, pH 7.4 and corresponds to H-TGL, was approximately half the activity from control rats. TGH released by heparin from isolated rat liver parenchymal cells was investigated. The enzyme activites released from isolated liver parenchymal cells prepared from STZ rats was approximately half that from control rats. The role of insulin in the regulation of LPL has been well documented. Our findings suggest that H-TGL also is under hormonal regulation by insulin in rats.

Glucocorticoids increase Ca2+ influx through dihydropyridinirsensitive channels linked to activation of protein kinase C in vascular smooth muscle cells

To clarify whether protein kinase is associated with glucocorticoid-induced Ca2+ influx into vascular smooth muscle cells, we investigated the effects of protein kinase inhibitors on dexamethasone-induced 45Ca2+ uptake and dihydropyridine binding in A7r5 cells. Protein kinase C inhibitors (staurosporine and UCN-01) abolished the dexamethasone-induced 45Ca2+ uptake and [methyl-3H]PN 200-110 binding. In contrast, KT5720 and KT5823, which are more specific inhibitors of cAMP-dependent protein kinase and cGMP-dependent protein kinase, respectively, did not affect the effects of dexamethasone. Treatment with 100 nM dexamethasone for 48 hours increased protein kinase C activity in A7r5 cells. These results suggest that glucocorticoids increase Ca2+ influx through dihydropyridine-sensitive channels, linked to activation of protein kinase C in vascular smooth muscle cells.

Primary Cardiac B-Cell Lymphoma

A 67-year-old woman was admitted to a hospital because of the recent onset of general malaise. She had a classic lilac-colored rash over her eyelids, the bridge of her nose, her cheeks, elbows, and knees and weakness in the proximal limb muscles. A diagnosis of dermatomyositis was confirmed by skeletal muscle biopsy. She was started on a course of oral glucocorticoids. Three months later, she complained of dyspnea. An echocardiogram revealed a massive pericardial effusion with evidence of both right atrial and ventricular collapse consistent with cardiac tamponade. Pericardiocentesis yielded 1000 mL of exudative bloody fluid with a lactate dehydrogenase value of 23 950 IU/L. Cytology revealed cells believed to represent lymphoma. The patient was referred to Fukui Medical School for …

Relation of angiographically defined coronary artery disease and plasma concentrations of insulin, lipid, and apolipoprotein in normolipidemic subjects with varying degrees of glucose tolerance

We investigated the association between hyperinsulinemia and changes in lipid, lipoprotein, and apolipoprotein that would increase the risk of coronary artery disease (CAD) independent of glucose tolerance. A coronary angiogram was recorded in 127 male subjects, including 41 with normal glucose tolerance, 41 with impaired glucose tolerance, and 45 with non-insulin-dependent diabetes mellitus (NIDDM). Subjects were divided into 2 groups according to results: the group with CAD (n = 94) and the group with normal coronary arteries (n = 33). All subjects were normolipidemic (total cholesterol < 230 mg/dl and triglycerides < 150 mg/dl). The CAD group had a significantly lower plasma level of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I (apo A-I) and a higher level of apolipoprotein B (apo B) than the normal group with normal glucose tolerance. In considering subjects with impaired glucose tolerance or NIDDM, the CAD group had a significantly lower plasma level of HDL cholesterol and apo A-I and a significantly higher plasma level of total cholesterol, triglycerides, and apo B than the normal group. In each of the subjects with normal and impaired glucose tolerance, and NIDDM, the elevation of plasma insulin concentration during both the complete test period and the early phase of an oral glucose challenge was significantly higher in the CAD than in the normal group. In all subjects, graded reductions in HDL cholesterol and apo A-I and graded increases in plasma total cholesterol, triglycerides, and apo B were observed with increasing tertiles of the postglucose challenge measurements of insulinemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Dexamethasone modulates the expression of endothelin-1 and -A receptors in A7r5 vascular smooth muscle cells.

Endothelin-1 (ET-1) is synthesized and released by vascular smooth-muscle cells (VSMCs). Glucocorticoids induce the release of ET-1 from VSMCs into the medium. We investigated whether glucocorticoids modulate ET-1 action by an autocrine production of ET-1 in A7r5 VSMCs. Dexamethasone (100 nM) stimulated the release of ET-1 into the medium. Treatment with 100 nM dexamethasone for 24 h reduced the peak increase of intracellular free Ca2+ induced by ET-1 (100 nM) by 50%, an effect that was dose-dependently inhibited by the specific ET(A)-receptor antagonist FR139317. Scatchard plots of [125I]-ET-1 binding revealed that dexamethasone reduced the number of maximal ET-1 binding sites without altering their binding affinity. FR139317 reversed the decrease in ET-1 binding capacity induced by dexamethasone. Northern blot analysis revealed that dexamethasone increased the level of prepro-ET-1 messenger RNA (mRNA) and decreased the level of ET(A)-receptor mRNA. FR139317 prevented the decrease in the level of ET(A)-receptor mRNA induced by dexamethasone. Results indicate that dexamethasone downregulates ET(A) receptors in A7r5 VSMCs at the mRNA level, in part by the autocrine production of ET-1.

The activation of nitric oxide synthase by copper ion is mediated by intracellular Ca2+ mobilization in human pulmonary arterial endothelial cells

1 The aim of the study was to elucidate the vasodilatory mechanism due to Cu2+ by assessing nitric oxide (NO) production as determined by NOx (NO, NO2−, and NO3−) that is released from human pulmonary arterial endothelial cell (HPAEC) monolayers using a NO chemiluminescence analyzer, and also to assess Ca2+ movement using 45Ca and fura 2 in HPAEC. 2 Cu2+ (10−6–10−4 m) significantly increased NO production in a dose‐dependent manner when extracellular Ca2+ was present. 3 45Ca influx into the adherent cells was dose‐dependently enhanced by Cu2+ (10−6–10−4 m), but not by Mn2+, Zn2+ or Fe2+. 4 [Ca2+]i, measured by monitoring the fluorescence changes of fura 2, was significantly elevated in the presence of Cu2+. 5 The increase in [Ca2+]i induced by Cu2+ was inhibited by either diethyldithiocarbamate (DDC) or the depletion of extracellular Ca2+. 6 The dihydropyridine receptor agonist, BayK8644, significantly attenuated the Cu2+‐induced increase in [Ca2+]i in a dose dependent manner and nitrendipine or nifedipine, the dihydropyridine receptor antagonists, dose‐dependently inhibited a Cu2+‐induced increase in [Ca2+]i. 7 These results suggest that Cu2+ activates eNOS through the mechanism of [Ca2+]i elevation due to Ca2+ influx into HPAEC and that the Cu2+‐induced [Ca2+]i elevation in HPAEC is likely due to activation of the dihydropyridine‐like receptors.

Diltiazem inhibits DNA synthesis and Ca2+ uptake induced by insulin, IGF-I, and PDGF in vascular smooth muscle cells

SummaryProliferation of vascular smooth muscle cells (VSMC) has been shown to play a key role in the atherosclerotic lesions. It has been demonstrated that serum-derived peptidic growth factors, such as insulin, platelet-derived growth factor (PDGF), or epidermal growth factor (EGF), provide mitogenic signals in VSMC and that the interplay of Ca2+ and other messengers is necessary for triggering proliferation. Since Ca2+ channel blockers act on the voltage-dependent Ca2+ channel to inhibit Ca2+ influx, it is conceivable that they affect the proliferative action of growth factors. In this study we have evaluated the effects of diltiazem, a 1,5-benzothiazepine-derived Ca2+ channel blocker, on [3H]thymidine incorporation into DNA stimulated by insulin, insulinlike growth factor I (IGF-I), or PDGF in cultured VSMC from rat aorta. We have also investigated the effects of insulin, IGF-I, and PDGF on Ca2+ uptake in VSMC. After exposure to insulin (10−10 to 8×10−6 M) or IGF-I (10−10 to 10−7 M) for 48 hours, VSMC incorporated [3H]thymidine to 200–280% of maximum (with insulin or IGF-I alone) compared to control. The effect of IGF-I was approximately 10–100 times more potent than that of insulin. PDGF (0.5–15 ng/ml) also induced an increase in [3H]thymidine incorporation into DNA of VSMC. Additivity is observed between PDGF with insulin or IGF-I, but not between insulin and IGF-I. Sixty minute treatment with insulin (5×10−8 to 10−6 M), IGF-I (10−8 to 10−6 M), or PDGF (1.0–15.0 ng/ml) increased the unidirectional45Ca2+ uptake during a 5 minute period. The 30 minute45Ca2+ uptake of insulin (10−7 to 10−6 M)- or IGF-I (10−8 to 10−7 M)-treated cells was significantly greater than that of nontreated cells; 3.5 ng/ml PDGF accelerated45Ca2+ uptake more than 10−6 M insulin or 10−7 M IGF-I. Diltiazem (10−9 to 2×10−5 M) inhibited not only the increase in [3H]thymidine incorporation but also that of the45Ca2+ uptake stimulated by insulin, IGF-I, or PDGF in a dose-dependent manner. These data suggest that coordinate control of VSMC proliferation by insulin or IGF-I and PDGF may play a cardinal role in the development of atherosclerosis and that a Ca2+ channel blocker may suppress atheroma formation by inhibiting VSMC proliferation evoked by serum-derived growth factors through a mechanism that attenuates the increase of intracellular Ca2+ concentration. Furthermore, the effects of insulin, IGF-I, and PDGF on proliferation of VSMC may be coupled to an increase of Ca2+ influx.

Effects of nicorandil on cell proliferation and cholesteryl ester accumulation in arterial smooth muscle cells in culture

SummaryCa2+ regulates a variety of cellular mechanisms in vascular cells as well as in platelets. Nicorandil interacts with the intracellular Ca2+-activated processes in vascular smooth muscle cells, while Ca2+ channel blockers such as verapamil and diltiazem block voltage-dependent Ca2+ channels. The effects of nicorandil are due to the hyperpolarization of the membrane, interference with mobilization of Ca2+ from the intracellular storage sites, and blockade of receptor-operated Ca2+ channels. In the present study, the effects of nicorandil on cell proliferation and cholesteryl ester accumulation in rat arterial smooth muscle cells in culture were compared to Ca2+ channel blockers. Smooth muscle cells were prepared from rat thoracic aorta, and the rate of proliferation was determined by measuring the cell number and by [3H]-thymidine incorporation into cellular DNA. The effect of nicorandil on cholesteryl ester content in smooth muscle cells was determined by thin-layer chromatography of the cell extracts. Nicorandil at concentrations of 10−6 to 10−4 M, as well as Ca2+ channel blockers (verapamil and diltiazem) inhibited the proliferation and DNA synthesis of cultured smooth muscle cells. The acute inhibitory effects on cell proliferation were observed significantly 16 hours after the addition of the three agents in serum-stimulated cells. These effects were dose dependent, both in acute and in chronic treatment with the three agents. Addition of 10−5 M nicorandil to medium supplemented with 10% serum resulted in a decrease of the net cholesteryl ester content by 18±1%, while cellular free cholesterol content was the same as control. Similar results were also obtained in the presence of verapamil and diltiazem. These data suggest that nicorandil may suppress atheroma formation, not only by inhibiting cell proliferation but also by decreasing cholesteryl ester accumulation in arterial smooth muscle cells.

The Characteristics of Renal Mineralocorticoid Receptors in Glycyrrhizinic Acid or Deoxycorticosterone-Induced Hypertensive Rats

The relationship between blood pressure and the characteristics of renal mineralocorticoid receptors was studied in glycyrrhizinic acid (GR) or deoxycorticosterone (DOC) induced hypertensive rats. The apparent maximum binding (Bmax) of aldosterone to renal mineralocorticoid receptors was 3.1 +/- 0.2 X 10(-13) mol/mg cytosol protein and the dissociation constant (Kd) was 1.6 +/- 0.5 nM. GR treatment reduced the concentration of cytosol mineralocorticoid receptors (Bmax) but did not affect the Kd. In unilaterally adreno-nephrectomized rats, GR induced hypertension and hypokalemia as seen in DOC treated rats. After the discontinuation of GR, blood pressure was normalized with concomitant recovery of free cytosol mineralocorticoid receptors in 14 weeks. On the contrary, in DOC treated rats, the characteristics of mineralocorticoid receptors in kidney were already normal one week after the cessation of DOC treatment. However, blood pressure remained high up to 15 weeks. These findings suggest that the persistence of hypertension after GR discontinuation might be caused by a long-standing effect of GR on renal mineralocorticoid receptor mechanisms.

A case of marked hemorrhagic cardiac tamponade induced by aortic wall perforation

心内膜炎を伴った感染性心内膜炎の加療中に重篤な出血性心タンポナーデを併発した1症例.心膜ドレナージ,輸血等にて心タンポナーデの症状・所見改善するも,心不全が増悪し,緊急大動脈弁置換術を施行した.術中所見にて,大動脈弁上部の上行大動脈壁に頭足方向に28mmの亀裂を認め,この部位からの出血により心タンポナーデが発症したことが示唆された.