Biomedical subjects

H Kanaide

Publications and source records attributed to H Kanaide.

At least 163 records · Page 9Linked to original sources

PubMed1987

Metabolic and physical changes during calcium paradox induced in the rat heart.

Early changes in metabolic and physical properties were determined in rat hearts during calcium paradox. Calcium paradox was induced under constant perfusion pressure (60 mmHg) or constant coronary flow rate (9.8 ml/min). Within 30 s after calcium repletion, in either case, NADH increased, despite a decrease in ATP and increases in ADP and AMP. Surface spectrophotometry showed a deoxygenation of the myoglobin, thereby indicating myocardial oxygen depletion. These changes were predominant under conditions of constant pressure perfusion. In association with a rapid development of contracture, there were also a reduction in coronary flow (18%) in constant pressure perfusion, and an increase in perfusion pressure (208%) under constant flow perfusion. Thus, tissue deoxygenation has to be given due attention in the early development of calcium paradox, particularly in case of a constant pressure perfusion. Under constant flow perfusion, the physical stress due to high pressure perfusion against contracture may play an important role in the development of calcium paradox. This may be the first reported evidence for tissue anoxia in calcium paradox.

Adenine Nucleotides↗

PubMed1986

Complete overlap of caffeine- and K+ depolarization-sensitive intracellular calcium storage site in cultured rat arterial smooth muscle cells.

Changes in the concentration of cytosolic free calcium were recorded microfluorometrically in rat vascular smooth muscle cells in primary culture and loaded with quin-2. The effects of caffeine and high extracellular K+ on the release of calcium from the intracellular storage sites were determined. In the absence of extracellular calcium, both the depolarization of plasma membrane with excess extracellular K+ and the application of caffeine induced a transient and dose-dependent elevation of the cytosolic free calcium concentration, with durations of 4 and 2 min, respectively. Transient elevations of calcium repeatedly appeared in response to both repetitive depolarization (100 mM K+) and caffeine (10 mM) applications with progressive reductions in peak levels. In either case, the fifth or later treatments induced little or no rise in levels of the cytosolic calcium. The amount of released calcium induced by high K+ depolarization after (n-1) time applications (1 less than or equal to n less than or equal to 5) of caffeine was equal to that induced by the n-th application of caffeine. The amount of released calcium induced by caffeine after (n-1) time exposures (1 less than or equal to n less than or equal to 5) to K+ depolarization was equal to that observed during the n-th exposure to K+ depolarization. These results indicate that caffeine- and depolarization-sensitive intracellular calcium storage sites may be identical and that caffeine and K+, in optimal concentrations, will release an equal amount of calcium from the same storage site in cultured arterial smooth muscle cells, irrespective of the amount of stored calcium.

Aminoquinolines↗

PubMed1986

Inhibition of calcium transients in cultured vascular smooth muscle cells by pertussis toxin.

Effects of pertussis toxin on Ca2+ transients in rat arterial smooth muscle cells in primary culture were monitored, using quin 2-microfluorometry. In the presence or the absence of extracellular Ca2+, norepinephrine, histamine, caffeine and high extracellular K+ induced elevations in cytosolic Ca2+ concentration. Cytosolic Ca2+ elevations induced by norepinephrine and histamine were inhibited by pretreatment of the cells with pertussis toxin, time- and dose-dependently. However, elevations induced by caffeine and K+-depolarization were unaffected by the pretreatment with this toxin. Thus, it is suggested that GTP binding protein, a pertussis toxin substrate and involved in the receptor-mediated cytosolic Ca2+ transients, is not involved in transient elevations in cytosolic Ca2+ induced by caffeine and K+-depolarization in cultured vascular smooth muscle cells.

Animals↗

PubMed1986

Intracellular free calcium transients induced by norepinephrine in rat aortic smooth muscle cells in primary culture.

In cultured rat arterial smooth muscle cells treated with quin 2, cytosolic Ca2+ transients induced by norepinephrine were recorded microfluorometrically. In the presence or absence of extracellular Ca2+, norepinephrine induced transient and dose-dependent elevations in cytosolic Ca2+, with a similar time course, the peak levels being observed at 2 min. These transient elevations in cytosolic Ca2+ were dose-dependently inhibited by alpha-adrenergic antagonists, the order of potency being prazosin greater than phentolamine greater than yohimbine, irrespective of the presence of extracellular Ca2+. We propose that with or without extracellular Ca2+, norepinephrine activates mainly alpha-1 adrenoceptors leading to a release of Ca2+ from intracellular stores. This would explain the transient elevation in cytosolic Ca2+ in rat aortic vascular smooth muscle cells in primary culture.

Aminoquinolines↗

PubMed1986

Histamine activates H1-receptors to induce cytosolic free calcium transients in cultured vascular smooth muscle cells from rat aorta.

Using an intracellularly trapped dye, quin 2, the effects of histamine on cytosolic free calcium concentrations in rat aortic vascular smooth muscle cells in primary culture were recorded, microfluorometrically. When the cells were exposed to histamine, both in the presence and the absence of extracellular Ca2+, there was a rapid, transient and dose-dependent elevation of cytosolic Ca2+ concentrations, with a similar time course. This elevation of cytosolic Ca2+ was dose-dependently inhibited by mepyramine, but not by cimetidine. Thus, histamine activates H1- but not H2- receptors to mediate a release of Ca2+ from the store sites, and there is a rapid and transient elevation of cytosolic Ca2+.

Aminoquinolines↗

PubMed1986

Binding of [3H]prazosin to porcine aortic membranes: interaction of calcium antagonists with vascular alpha-1 adrenoceptors.

The characteristics of [3H]prazosin binding and the interaction of Ca antagonists with alpha-1 adrenoceptors in the porcine aortic membranes were investigated. The binding characteristics of [3H]prazosin, namely, the kinetics and affinity of binding, saturability, competition by adrenergic agonists and antagonists, stereoselectivity and the localization of binding sites, indicated that [3H]prazosin binds specifically to the alpha-1 adrenoceptors in the sarcolemma of porcine aortic smooth muscle cells. In the inhibition study by several Ca antagonists, the specific binding of [3H]prazosin to aortic membranes was inhibited by verapamil (Ki = 0.66 microM), D600 (Ki = 0.86 microM), nicardipine (Ki = 2.3 microM) and d-cis diltiazem (Ki = 9.8 microM). Nifedipine and nitrendipine, potent dihydropyridine Ca antagonists, only partially inhibited the [3H]prazosin binding, up to 10(-4) M. l-Cis and dl-trans diltiazem, the less potent stereoisomers as Ca channel blockers compared with the d-cis form, showed a similar and greater potency as a competitor to alpha-1 adrenoceptors, respectively. These observations indicate that verapamil, D600, nicardipine and diltiazem interact with vascular alpha-1 adrenoceptors and that the potency of these compounds as a competitor to alpha-1 adrenoceptors does not parallel their potency as Ca channel blockers.

Animals↗

PubMed1986

Binding of [3H]-nitrendipine and [3H]-diltiazem to rat myocardial sarcolemma.

The binding properties of two major and chemically distinct calcium antagonists, [3H]-nitrendipine and [3H]-diltiazem, were investigated in highly purified rat cardiac sarcolemma. In the case of [3H]-nitrendipine, there appeared a single set of high affinity binding sites with a B max of approximately 0.9 pmol X mg-1 protein and a KD of approximately 0.15 nmol/l. Because of the extremely high value obtained for KD (29 mumol/l), the specificity of [3H]-diltiazem binding seemed questionable. The specific binding of 0.1 nmol/l [3H]-nitrendipine to cardiac sarcolemma was inhibited by nitrendipine and nifedipine (1 mumol/l), only partly inhibited by verapamil (1 mumol/l), and was enhanced by diltiazem (0.1-10 mumol/l). The stimulation of [3H]-nitrendipine binding by diltiazem was associated with an increase in the number of binding sites, Bmax, but with no change in the KD or the Hill coefficient. An enantiomer of diltiazem (1-cis) neither stimulated nor inhibited the [3H]-nitrendipine binding. These results strongly suggest that major prototype calcium antagonists have distinct and variously interacting sites of action in the rat cardiac sarcolemma.

Animals↗

PubMed1986

Adriamycin and altered membrane functions in rat hearts.

To evaluate the potential roles of alterations of membrane functions and resulting calcium overload in the pathogenesis of acute adriamycin cardiotoxicity, we observed sarcolemmal, sarcoplasmic reticular and mitochondrial functions in isolated hearts perfused by the Langendorff technique and exposed to adriamycin. Myocardial tissue calcium content was increased to 120 and 130% of the control level after 30 and 60 min perfusion with adriamycin (50 micrograms/ml), respectively. Sarcolemmal ouabain-sensitive Na+,K+-ATPase activity was decreased by 46% after 30 min perfusion, compared with the control. Mitochondrial calcium uptake was also depressed but sarcoplasmic reticular calcium uptake and binding remained unaltered. Mitochondrial respiratory activity was depressed after 60 min perfusion, when glutamate was used as a substrate, thereby indicating that adriamycin had an inhibitory effect on the NADH-dehydrogenase system. Thus, among membrane functions directly or indirectly regulating calcium movement, the inhibition of enzyme systems susceptible to lipid peroxidation may play important roles in calcium overload induced by adriamycin.

Animals↗

PubMed1985

Cytosolic-free calcium transients in cultured vascular smooth muscle cells: microfluorometric measurements.

Microfluorometric recordings were made of changes in the concentration of cytosolic-free calcium in cultured rat vascular smooth muscle cells treated with quin 2, an intracellularly trapped dye, under several conditions. Nitroglycerin decreased calcium in both the presence and absence of extracellular calcium and strongly and progressively decreased the extent of transient increases in calcium induced by repeated applications of caffeine in the absence of extracellular calcium. Therefore nitroglycerin probably decreases cytosolic-free calcium by accelerating the extrusion of calcium through the sarcolemmal membrane.

Aminoquinolines↗

PubMed1985

K+-depolarization induces a direct release of Ca2+ from intracellular storage sites in cultured vascular smooth muscle cells from rat aorta.

Using an intracellularly trapped dye, quin 2, effects of K+-depolarization on cytosolic free calcium concentrations were recorded microfluorometrically in rat aorta vascular smooth muscle cells in primary culture. When the cells were exposed to high extracellular K+ in Ca+-free media containing 2mM EGTA, there was a transient and dose-dependent elevation of cytosolic Ca2+ concentrations. However, the concentration of the cytosolic Ca2+ was not elevated when the intracellularly stored Ca2+ was depleted by the repetitive treatment with caffeine prior to the application of high K+. Thus depolarization of plasma membrane, per se, directly induces a release of Ca2+ from intracellular storage sites in vascular smooth muscle cells, and the main fraction of this released Ca2+ is derived from the caffeine sensitive storage sites; perhaps from the sarcoplasmic reticulum.

Aminoquinolines↗

PubMed1985

Specific binding of [3H] mepyramine to histamine H1-receptors in the sarcolemma from porcine aorta and coronary artery.

We studied the subcellular distribution and the properties of [3H] mepyramine binding in the porcine vascular smooth muscle. A close correlation was observed between the specific binding activity of [3H] mepyramine and the extent of the enrichment of sarcolemmal marker enzyme in 4 subfractions obtained by sucrose density gradient centrifugation of the aortic microsome. In the binding isotherm in the sarcolemmal fractions from the aorta and coronary artery, there was no difference in the Kd value, but the Bmax of the coronary artery was significantly lower than that of the aorta. Thus, there is a single type of high affinity mepyramine binding site in the porcine vascular smooth muscle sarcolemma and the number of H1-receptors of the coronary artery may be smaller than that of the aorta.

Aminopyridines↗

PubMed1985

Coronary venous perfusion of the ischemic myocardium during acute coronary artery occlusion in isolated rat hearts.

Effects of retrograde coronary venous perfusion on oxygen supply and energy metabolism of ischemic myocardium of the isolated perfused rat heart were examined by means of NADH fluorescence photography. Occlusion of the left coronary artery produced regional ischemia of the left ventricular free wall, as evidenced by the sharply demarcated increase in NADH fluorescence. During ischemia, a narrow area of minimal fluorescence (140 +/- 10 microns), indicating sufficient oxygenation for oxidative phosphorylation, was observed around the epicardial coronary veins in the ischemic lesion. Retrograde perfusion was introduced through the coronary vein (left cardiac vein) that drained off the ischemic area, which resulted in a marked reduction of the area of increased NADH fluorescence in the epicardial surface. In the cross-sectional view, although the myocardium of the entire ischemic area induced by left coronary artery occlusion could be perfused by venous retroperfusion, the effect on reduction of the area of increased NADH fluorescence was seen only in the epicardial half of the myocardium. Retrograde coronary venous perfusion also resulted in a small increase in tension development (P less than 0.05), a decrease in resting tension (P less than 0.01), and partial preservation of myocardial high energy phosphate content (P less than 0.01). We propose that coronary venous retroperfusion improves oxygenation, partially preserves oxidative phosphorylation in the epicardium, and improves contractile function in the ischemic region.

Acute Disease↗

PubMed1985

Effort angina without coronary obstruction in a patient with Takayasu's aortitis: a case report.

Angina occurring in patients with Takayasu's aortitis is attributed to the narrowing of the coronary ostium and/or aortic regurgitation. We treated a patient with Takayasu's aortitis with effort angina, in whom there was no obstruction of the ostium or aortic regurgitation. Treadmill exercise stress test revealed significant ST depression in leads V4-6, II, III and aVF with chest pain. Examinations of lactate in coronary sinus as well as arterial blood suggested the occurrence of myocardial ischemia during atrial pacing. The DPTI/TTI index was decreased and the left ventricular end-diastolic pressure was increased during angina. It is considered that the reduced coronary perfusion pressure resulted from a low diastolic aortic pressure and the elevated left ventricular end-diastolic pressure decreased the DPTI/TTI index and contributed to the development of subendocardial ischemia.

Adult↗

PubMed1985

Changes in subcellular calcium transport in rat hearts during the calcium paradox.

Changes in the transport of calcium in the sarcoplasmic reticulum (SR) and mitochondria (MT), of the rat heart during calcium paradox were investigated. Calcium binding and uptake by SR in the paradox hearts were from about 1.5 to 2 times greater than in normal hearts, whereas in the MT of the paradox hearts they were about half those of normal hearts. There was no difference between paradox and normal hearts in calcium stimulated ATPase activity in the SR. The ultrastructure of the MT was disrupted in calcium paradox, but the SR was essentially the same as in normal hearts. We propose that during calcium paradox, the intracellular calcium overload damages both calcium transport and the ultrastructure of the MT, but that calcium transport by the SR is accelerated to compensate for the calcium overload.

Adenosine Triphosphatases↗

PubMed1985

The distribution of ischaemia in perfused Wistar rat hearts following coronary artery occlusion.

Ischaemia induced in Wistar rat hearts by ligation of the main coronary arteries, was studied by NADH-fluorescence photography. The coronary anatomy was examined by barium angiography and intravascular resin infusion and it was confirmed that the main arteries were the left and right coronaries and the septal artery. The septal artery branched from the right coronary orifice in 90% of hearts examined. The long-axial cross-sectional view of the heart showed the ischaemic area to be limited to the left ventricular free wall following ligation of the left coronary, to the right ventricular free wall following ligation of the right coronary artery and to the ventricular septum after ligation of the septal artery. When the left coronary artery was ligated at its origin, the ratio of ischaemic area to cross-sectional area increased from the base to the apex of the heart. The borders of the epicardial ischaemic area induced by left and right coronary ligation made contact without any overlapping or broad separation. This indicates that the area perfused by the left and right coronary arteries was contiguous but physically separated.

Animals↗

PubMed1985

Rat vascular smooth muscle cells in culture contract upon Ca2+ repletion after depletion.

We investigated the effects of Ca2+-repletion following depletion on cultured vascular smooth muscle cells (SMCs) from the rat aorta. With Ca2+-repletion, the cells in primary cultures contracted, as indicated by a decrease in cell area. The process was slow (30 min to maximum effect) and reversible (relaxation completed by 120 min). Contraction during Ca2+-repletion was never observed in subcultured cells. The SMCs in primary culture after treatment maintained the ability to grow and to exclude dye, with a normal plating efficiency. There was no treatment-related additional leakage of intracellular enzymes, LDH and CPK, into the medium. Ca2+-repletion at first accelerated the 45Ca uptake by SMCs (1-5 min after repletion) and then increased Ca2+ efflux after about 10 min of Ca2+-repletion. We conclude that Ca2+-repletion after depletion induces a transient and reversible contraction of vascular SMCs in primary culture, without cell injury and in association with a transient increase in Ca2+ influx and then efflux. This phenomenon may relate to the decrease in perfusion flow in hearts and kidneys during Ca2+-repletion after depletion (Ca2+-paradox).

Animals↗

PubMed1984

Toxicity of renal lysosomal contents on aortic smooth muscle cells in culture.

Effects of hog renal lysosomal contents and renin on cultured rat aortic smooth muscle cells (SMCs) were studied in attempts to determine mechanisms related to production of arterial lesions. The lysosomal contents rich in renin and with the pressor and the cytotoxic effects in vivo, inhibited the plating efficiency of SMCs in a dose- and incubation time-dependent manner. No inhibition occurred with the purified hog renin. The possibility that renal lysosomal contents contain a substance(s), other than renin, which has a direct toxic effect on vascular SMCs has to be given attention.

Animals↗

PubMed1984

Total adenine nucleotide stores and sarcoplasmic reticular Ca transport in ischemic rat heart.

We studied the relation between the contractility and metabolic changes in reperfusion after ischemia, and the effect of diltiazem on these changes, in an isolated rat heart perfused using the Langendorff method. After aerobic perfusion at 80 cmH2O, the perfusion pressure was reduced to 10 cmH2O to induce global ischemia. Substrate was removed from the perfusate during ischemia. After 30 or 60 min of ischemia, the heart was reperfused in an aerobic condition. During ischemia, the total adenine nucleotide level (TAN: sum of ATP, ADP, and AMP) was progressively reduced and the ATP-to-ADP ratio was one-third of the value obtained in an aerobic condition. With 30 min of subsequent reperfusion, ATP increased, and the shorter the duration of ischemia, the closer ATP/ADP approached the value of an aerobic condition, whereas TAN was equivalent to the value shown immediately before reperfusion. Thus the degree of ATP recovery by reperfusion mainly depends on the amount of TAN immediately before reperfusion and the mitochondrial function of oxidative phosphorylation that determines ATP/ADP. The calcium transport activity of the sarcoplasmic reticulum of myocardial cells was affected by ischemia and showed no amelioration or further deterioration by subsequent reperfusion. When diltiazem (10(-5)M) was added to the perfusate continuously from 5 min before ischemia, during ischemia, and until 10 min of reperfusion, the amount of TAN in ischemia and reperfusion and the calcium transport activity during reperfusion were maintained at relatively high levels. The degree of contractility recovery by reperfusion showed direct correlations with both the tissue ATP amount and the level of calcium transport activity in the sarcoplasmic reticulum.

Adenine Nucleotides↗