Glucose transporter recycling in rat adipose cells. Effects of potassium depletion

Depletion of intracellular potassium (K+) induced a 4-fold increase in basal and 1 microM phorbol-12-myristate-13-acetate (PMA)-stimulated 3-O-methylglucose transport in rat adipose cells. K+ depletion had no effect on the maximum insulin (0.7 microM)-stimulated transport rate but enhanced the sensitivity to insulin 3-fold (EC50 = 0.05 versus 0.15 nM) by a mechanism that did not result from changes in the insulin receptor binding, autophosphorylation, or tyrosine kinase activity. Western blotting analysis revealed that K+ depletion induced a 2.2-fold increase in GLUT4 in plasma membranes from basal cells, enhanced the PMA-stimulated GLUT4 translocation by 4-fold, and increased the 5-fold insulin-stimulated GLUT4 translocation by 15%, indicating the presence of an inactive GLUT4 intermediate. The time course for insulin's stimulation of transport activity was accelerated by K+ depletion (t1/2 = 3 versus 1.5 min). Conversely, the reversal of transport activity, on removal of insulin, was delayed (t1/2 = 11 versus 22 min). The corresponding t1/2 values for the loss of GLUT4 were 22 min in control cells and 40 min in K(+)-depleted cells, again indicating the existence of an inactive intermediate. Photolabeling intact cells with the impermeant, exofacial photolabel 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 - yloxy)-2-propylamine in the continuous presence of insulin revealed that K+ depletion had no effect on the GLUT4 externalization rate but halved the rate of internalization. K+ depletion elicited entirely analogous effects on the recycling of insulin-like growth factor II/mannose 6-phosphate receptor, strongly supporting the involvement of a coated pit mechanism in the recycling of GLUT4 transporters. An inactive conformation of GLUT4 has been detected in plasma membranes from insulin-stimulated cells, which is enhanced by K+ depletion, suggesting a limitation in the adipose cells' capacity to express active GLUT4 transporters.

Disseminated pancreatic polypeptidioma

Pancreatic polypeptidioma, a pancreatic endocrine tumor, is an extremely uncommon disease and its clinical features and responses to therapy are not well known. We present a 33-year-old woman with disseminated pancreatic polypeptidioma, who subsequently showed various signs and symptoms of metastases, including bone pain, cranial nerve palsy, spinal block, and hematuria, and died 22 months after the presentation. Responses to various therapeutic regimens including hepatic arterial embolization, radiation therapy, systemic chemotherapy, and administration of interferon-alpha or somatostatin analogue, are discussed. Particular note in this case is a prompt response of bone metastases to the radiotherapy.

Long-term alpha 1 blockade does not reverse cardiac hypertrophy in spontaneously hypertensive rats

Not all antihypertensive drugs induce regression of left ventricular (LV) hypertrophy in hypertension, although they may equally lower blood pressure. The effects of alpha 1-blockers on regression have been inconsistent. In this study, bunazosin, a selective alpha 1-blocker, (15 mg/kg/day in food) was given to male spontaneously hypertensive rats (SHR) from 15 to 35 weeks of age to evaluate its effects on cardiac hypertrophy, hemodynamics, and neurohumoral factors. Age- and sex-matched SHR served as controls. LV function and cardiac output were determined by a micromanometer and thermodilution, respectively. Bunazosin significantly decreased blood pressure in conscious rats (from 209 to 192 mmHg, p < 0.01) but did not reduce LV mass. Heart rate, LV end-diastolic pressure, dp/dtmax, and cardiac output were similar in the 2 groups. Plasma renin activity was unaltered but plasma norepinephrine levels were higher in the treated rats (p < 0.05). Thus, bunazosin produced a significant relative reduction of blood pressure but did not reverse LV hypertrophy in SHR. Inadequate afterload reduction (8%) due to severe hypertension (> 200 mmHg) may explain the absence of regression. The rise of plasma norepinephrine levels may also offset the beneficial effects of bunazosin.

Use of bismannose photolabel to elucidate insulin-regulated GLUT4 subcellular trafficking kinetics in rat adipose cells. Evidence that exocytosis is a critical site of hormone action

The subcellular trafficking of tracer-tagged GLUT4 between the plasma membranes and low-density microsomes of rat adipose cells has been studied. Cell-surface GLUT4 have been initially tracer-tagged in the insulin-stimulated state with the [3H]bismanose photolabel 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(D-mannos- 4-yloxy)-2- propylamine. The half-time for internalization of tracer-tagged GLUT4 when insulin is removed by collagenase treatment is similar to that observed for the decrease in immunodetectable GLUT4 in the plasma membranes and the decrease in glucose transport activity in the intact cells. In contrast, internalization of tracer-tagged GLUT4 also occurs when cells are maintained in the continuous presence of insulin even though the plasma membrane level of immunodetectable GLUT4 and glucose transport activity in the intact cells are unaltered. These data show, for the first time, that insulin has little, if any, effect on the rate constant for GLUT4 endocytosis, but instead, primarily increases the rate constant for exocytosis. Tracer-tagged GLUT4 that is returned to the low-density microsomes can be restimulated with fresh insulin to recycle to the plasma membranes and to a steady-state distribution level that is the same as that observed in cells that are maintained in the continuous presence of insulin. These data suggest that the cells' entire complement of GLUT4 is involved in the recycling process. Following insulin stimulation of adipose cells initially in the basal state, the increase in immunodetectable GLUT4 in the plasma membranes precedes the increase in accessibility of GLUT4 to exofacial 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2- propylamine photolabeling, and this in turn precedes the increase in cellular glucose transport activity. Such time course data suggest that there may be plasma membrane intermediate states in the GLUT4 trafficking pathway. The kinetic properties of GLUT4 translocation and its recycling have been interpreted in terms of a subcellular trafficking model that identifies exocytosis, possibly involving-hypothetical "docking" and "fusion" steps, as the critical site of hormone action.

Isolation and characterization of a thiamin pyrophosphokinase gene, THI80, from Saccharomyces cerevisiae

The thi80 mutant of Saccharomyces cerevisiae (Nishimura, H., Kawasaki, Y., Nosaka, K., Kaneko, Y., and Iwashima, A. (1991) J. Bacteriol. 173, 2716-2719) shows markedly reduced activity of thiamin pyrophosphokinase (TPK; EC 2.7.6.2). We have isolated a DNA fragment carrying the THI80 gene from a yeast genomic library by its ability to complement constitutive synthesis of the thiamin-repressible acid phosphatase, encoded by the PHO3 gene, of thi80 mutant cells. On the other hand, the thi80 locus was found to be located 3.3 centimorgans proximal to the smp3 locus on the right arm of chromosome XV by genetic mapping analysis, and one more fragment bearing the THI80 gene trailing SMP3 gene was obtained by the plasmid eviction method. The nucleotide sequence of the overlapped region between the two isolated DNAs contained an open reading frame of 957 base pairs, encoding a 319-amino acid polypeptide with a calculated molecular weight of 36,616. When the intact THI80 open reading frame was expressed as a fusion protein carrying three vector-encoded amino acids at its N terminus in Escherichia coli lacking TPK, marked TPK activity was detected in the procaryotic cells, proving that the THI80 gene of S. cerevisiae encodes a structural gene of TPK. A gene disruption experiment demonstrated that the THI80 gene was essential for growth, and therefore, revealed that TPK is the only enzyme capable of synthesizing thiamin pyrophosphate in yeast. Studies of Northern blot analysis and the enzyme assay demonstrated that the THI80 gene expression is regulated mainly at the mRNA level by the intracellular thiamin pyrophosphate and requires the positive regulatory factors encoded by THI2 and THI3 genes. However, unlike thiamin-repressible acid phosphatase and the enzymes involved in thiamin synthesis of S. cerevisiae, TPK was found to be expressed constitutively at a low level and incompletely repressed by exogenous thiamin.

Construction of an antigenic map of the haemagglutinin-esterase protein of influenza C virus

Four different antigenic sites (A-1, A-2, B-1, B-2) have been identified previously on the haemagglutinin-esterase (HE) glycoprotein of influenza C/Ann Arbor/1/50 virus with seven monoclonal antibodies (MAbs). In this study we produced 30 additional anti-HE MAbs, nine of which demonstrated at least one of the following activities: haemagglutination inhibition, receptor-destroying enzyme inhibition, haemolysis inhibition, and neutralization (group A). The remaining had none of these activities (group B). These antibodies, and those previously isolated, were used to construct a more complete antigenic map of the HE molecule. Operational and topological analyses showed that a minimum of nine non-overlapping or partially overlapping antigenic sites were present on the HE protein, five recognized by group A MAbs (A-1 to A-5) and four by group B (B-1 to B-4). Among these antigenic sites, site A-5 was unique in that MAbs to this site inhibited the receptor-destroying activity without influencing the receptor-binding activity, which supports the idea that the sites responsible for these two functions are separate. It was also found that several group B MAbs were cross-reactive with host cell antigens.

Rescue of neuronal function by cross-regeneration of cutaneous afferents into muscle in cats

1. This study investigates the relation between the peripheral innervation of low-threshold cutaneous afferents and the postsynaptic potentials elicited by electrical stimulation of those afferents. 2. In cats deeply anesthetized with pentobarbital sodium, cord dorsum potentials (CDPs) and postsynaptic potentials (PSPs) in spinal motoneurons were elicited by stimulation of the caudal cutaneous sural nerve (CCS), the lateral cutaneous sural nerve (LCS), and the medial gastrocnemius (MG) muscle nerve. We tested 1) unoperated cats, and cats in which CCS has been 2) chronically axotomized and ligated, 3) cut and self-reunited, 4) cut and cross-united with LCS, or 5) cut and cross-united with the MG. Terminal experiments were performed 3-36 mo after initial surgery. 3. In cats in which the CCS had been self-reunited or cross-united distally with LCS, tactile stimulation of the hairy skin normally innervated by the distal nerve activated afferents in the CCS central to the coaptation, indicating that former CCS afferents had regenerated into native or foreign skin, respectively. 4. In cats in which the CCS had been cross-united distally with the MG, both stretch and contraction of the MG muscle activated the former CCS afferents. 5. In unoperated cats, CDPs elicited by stimulation of CCS and of LCS exhibited a low-threshold N1 wave and a higher-threshold N2 wave. These waves were greatly delayed and appeared to merge after chronic axotomy of CCS. Regeneration of CCS into itself, into LCS, or into MG restored the normal latencies and configurations of these potentials. 6. In unoperated cats, stimulation of CCS, of LCS, and of MG each produced PSPs of characteristic configurations in the various subpopulations of motoneurons of the triceps surae. CDPs and PSPs elicited by the CCS cross-regenerated into LCS or MG were typical of those generated by the normal CCS, i.e., there was no evidence of respecification of central synaptic connections to bring accord between center and periphery after cross-regeneration. 7. Chronic axotomy of CCS increased the latencies of PSPs from CCS; regeneration of CCS into the CCS, LCS, or MG restored normal latencies. 8. In summary, CDPs and PSPs in motoneurons from the cutaneous sensory nerve CCS are altered by chronic axotomy of CCS, thus indicating their target dependency. These alterations are restored by regeneration of CCS into not only a native or foreign cutaneous target, but also into skeletal muscle. We conclude that muscle as well as skin is capable of providing trophic support for cutaneous afferents.

[A case of bronchial artery aneurysm communicating with pulmonary artery]

A 48-year-old man was admitted to our hospital because of an abnormal shadow on the chest rentogenogram detected by the regular health screening. A tumorous shadow about 10 mm in diameter existed in the right lower lobe on chest X-ray film. It was suggested that the tumor was receiving blood flow from the aortic system by IVDSA and dynamic CT, right bronchial angiogram demonstrated a dilatation and aneurysm formation associated with anastomosis of the pulmonary artery. Aneurysmectomy and right bronchial arterial ligation were performed, and no other complication was observed. Bronchial artery aneurysm is a rare disease, and 25 cases have been previously reported in the literature in Japan.

Ampicillin concentrations in radicular cysts following a single oral administration of bacampicillin

1. Ampicillin concentrations in cyst wall (wall) and cyst fluid (fluid) of radicular cyst and serum following a single oral administration of bacampicillin (equivalent to 500 mg of ampicillin) were measured by a paper disk method. 2. The mean peak concentrations of ampicillin in wall, fluid, and serum occurred at identical times, 1.5 hr, and were 2.39 micrograms/g, 0.77, and 10.24 micrograms/ml, respectively. 3. Mean ampicillin concentration ratios of wall/serum, fluid/serum, and fluid/wall at the peak time were 0.23, 0.07, and 0.40, respectively. 4. Mean ampicillin concentrations in wall and fluid at the peak time exceeded MIC (minimum inhibitory concentration) for 90% (0.5 microgram/ml) for clinically isolated strains of alpha-hemolytic Streptococci.

Myelo-monocytoid immunophenotypes of B-cell chronic lymphocytic leukemia cells

Leukemia cells from ten patients with B-cell chronic lymphocytic leukemia (B-CLL) and one with B-CLL of mixed cell type (B-CLL/PL) were analyzed to delineate the cellular characteristics, especially the myelomonocytic nature. Most of the surface phenotypes were consistent with the previous reports. However, the frequency of positivity for CD22 and CD25 was much higher in the examined cases of B-CLL than in Western reports. B-CLL cells frequently possessed antigens which are mainly expressed in myelomonocytic cells: 8/10 for CD11b and 4/10 for CD11c, although the presence of CD14 was not apparent (0/10). In addition, colony stimulating factor-1 receptors (CSF-1R) were expressed in 6 of the 10 B-CLL cases. The reactivity with antigens such as CD14, CD11c, and CSF-R was markedly enhanced by in vitro incubation. Alterations in antigen expression and in in vitro survival by growth factors for myelomonocytic lineage were observed in certain cases. These data imply that not only are B-CLL cells phenotypically closely related to myelomonocytic lineage but that they may also be influenced by growth factors for that lineage.

Mixed haplotype A beta Z/A alpha d class II molecule in (NZB x NZW)F1 mice detected by T cell clones

We have tried to demonstrate the existence of a mixed haplotype MHC class II molecule in (NZB x NZW)F1 (B/WF1) mice. When a large panel of keyhole limpet hemocyanin-specific T cell clones derived from B/WF1 mice was analyzed, several clones were shown to be restricted by a F1-specific A beta Z/A alpha d class II molecule. Autoreactive A beta Z/A alpha d-specific T cell clones were also obtained. The ability of the association and expression of A beta Z with A alpha d was confirmed by hybridoma and transfection experiments. Hybridoma cell lines created by fusion of NZW (H-2z) spleen cells with M12.C3 (a A beta d- variant cell line derived from M12.4.1 (H-2d) B lymphoma) cells expressed A beta Z determinants. Transfection of A beta Z genomic DNA to M12.C3 cells resulted in the expression of A beta Z determinants. These hybridoma cell lines and transfectants were able to stimulate A beta Z/A alpha d-specific T cell clones, suggesting the expression of A beta Z/A alpha d molecules on the cell surface. However, attempts to demonstrate the existence of mixed haplotype MHC class II molecules in B/WF1 mice by two-dimensional (nonequilibrium pH gradient gel electrophoresis/SDS-PAGE) gel electrophoresis analysis with the use of anti-class II mAb failed to demonstrate the existence of mixed haplotype A beta Z/A alpha d or A beta d/A alpha z class II molecules in B/WF1 mice. Analysis of mixture of TA beta Z cell and B/WF1 spleen cell lysates immunoprecipitated by anti-A beta Z mAb suggested that the amount of haplotype mixed A beta Z/A alpha d molecules in B/WF1 spleen cells is less than 1/10 that of haplotype matched A beta/A alpha pairs. Our results suggest that, although undetectable by biochemical analysis, small amounts of mixed haplotype A beta Z/A alpha d molecules exist in B/WF1 spleen cells. Also, T cell clones which recognize them exists in B/WF1 mice. Because autoimmune symptoms of B/WF1 mice are shown to be related to heterozygosity at the H-2 region, autoreactive T cell clones which recognize the mixed haplotype A beta Z/A alpha d class II molecule might be involved for the induction of autoimmunity in B/WF1 mice.

Mixed haplotype A beta Z/A alpha d class II molecule in (NZB x NZW)F1 mice detected by T cell clones

We have tried to demonstrate the existence of a mixed haplotype MHC class II molecule in (NZB x NZW)F1 (B/WF1) mice. When a large panel of keyhole limpet hemocyanin-specific T cell clones derived from B/WF1 mice was analyzed, several clones were shown to be restricted by a F1-specific A beta Z/A alpha d class II molecule. Autoreactive A beta Z/A alpha d-specific T cell clones were also obtained. The ability of the association and expression of A beta Z with A alpha d was confirmed by hybridoma and transfection experiments. Hybridoma cell lines created by fusion of NZW (H-2z) spleen cells with M12.C3 (a A beta d- variant cell line derived from M12.4.1 (H-2d) B lymphoma) cells expressed A beta Z determinants. Transfection of A beta Z genomic DNA to M12.C3 cells resulted in the expression of A beta Z determinants. These hybridoma cell lines and transfectants were able to stimulate A beta Z/A alpha d-specific T cell clones, suggesting the expression of A beta Z/A alpha d molecules on the cell surface. However, attempts to demonstrate the existence of mixed haplotype MHC class II molecules in B/WF1 mice by two-dimensional (nonequilibrium pH gradient gel electrophoresis/SDS-PAGE) gel electrophoresis analysis with the use of anti-class II mAb failed to demonstrate the existence of mixed haplotype A beta Z/A alpha d or A beta d/A alpha z class II molecules in B/WF1 mice. Analysis of mixture of TA beta Z cell and B/WF1 spleen cell lysates immunoprecipitated by anti-A beta Z mAb suggested that the amount of haplotype mixed A beta Z/A alpha d molecules in B/WF1 spleen cells is less than 1/10 that of haplotype matched A beta/A alpha pairs. Our results suggest that, although undetectable by biochemical analysis, small amounts of mixed haplotype A beta Z/A alpha d molecules exist in B/WF1 spleen cells. Also, T cell clones which recognize them exists in B/WF1 mice. Because autoimmune symptoms of B/WF1 mice are shown to be related to heterozygosity at the H-2 region, autoreactive T cell clones which recognize the mixed haplotype A beta Z/A alpha d class II molecule might be involved for the induction of autoimmunity in B/WF1 mice.

Cardiopulmonary function after pulmonary lobectomy in patients with lung cancer

The effects of pulmonary lobectomy on cardiopulmonary function were investigated in 9 patients with lung cancer. Hemodynamic studies at rest and during exercise were performed before and 4 to 6 months after the operation. Differences in hemodynamics between before and after operation were observed with respect to heart rate, pulmonary arterial pressure, pulmonary vascular resistance index, and stroke volume index. Heart rate, pulmonary arterial pressure, and pulmonary vascular resistance index were significantly increased after operation, whereas stroke volume index was significantly decreased. It is thought that cardiac index was preserved by the increase in heart rate despite a decrease in stroke volume index associated with the decreased pulmonary vascular bed after the operation. When driving pressure and cardiac index were studied after operation, the pressure at rest and during exercise was higher, and the pressure-flow curve increased more steeply, as compared with the preoperative values. These results suggest a significant deterioration in cardiopulmonary function after lobectomy. As the patient characteristics were heterogeneous (five lobectomies and four bilobectomies), and their findings are limited, additional studies may be necessary in the future.

Effects of prolonged application of isoprenaline on intracellular free magnesium concentration in isolated heart of rat

1. The effect of prolonged application of isoprenaline on intracellular free-Mg2+ concentration ([Mg2+]i) was examined by use of 31P-nuclear magnetic resonance (31P-n.m.r.) in rat isolated hearts. Left ventricular pressure (LVP) was simultaneously measured. 2. [Mg2+]i was estimated from the separation of the alpha- and beta-ATP peaks, using the dissociation constant of MgATP 38 microM (established previously). In normal (phosphate-free, Krebs-Henseleit) solution, [Mg2+]i was approximately 0.4 mM. 3. When isoprenaline was applied for 100 min, a transient increase in [Mg2+]i was observed during the initial 25 min, whilst concentrations of ATP ([ATP]) and phosphocreatine ([PCr]) decreased and [Pi] correspondingly increased. During the subsequent 75 min of isoprenaline application, [Mg2+]i decreased below its resting levels. Washout of isoprenaline restored [Mg2+]i and [PCr], but [ATP] remained low. These changes elicited by isoprenaline were not observed in the presence of propranolol, a typical alpha-adrenoceptor blocker. 4. Isoprenaline increased both LVP and heart rate. The increased LVP and heart rate slowly returned to lower values during prolonged application of isoprenaline, but remained higher than those before application. 5. The transient rise in [Mg2+]i elicited by isoprenaline could be attributed to the decrease in [ATP] resulting in a release of Mg2+. The subsequent decrease in [Mg2+]i during the prolonged applications suggests that beta-adrenoceptor stimulation itself facilitates Mg(2+)-extruding mechanism(s).

Induction chemoradiotherapy followed by surgery for stage III non-small cell lung cancer

Twenty-five patients with stage III, non-small cell lung cancer were treated with cisplatin-based chemotherapy and thoracic radiation therapy followed by surgery. Thirteen patients had stage IIIA disease and 12, stage IIIB disease. The chemotherapy and radiotherapy were intensively combined with only a few days' interval between them. Radiation therapy delivering a total dose of 50-70 Gy was started 10 days after the beginning of chemotherapy. A few additional courses of chemotherapy were repeated until a thoracotomy was performed. All but two surgically-treated patients underwent tumor resection, with 19 lobectomies and four pneumonectomies. Eighteen patients underwent curative and five, non-curative resections. Pathological examination of the resected specimen provided accurate intrathoracic information. Six patients (24%) showed a pathologically complete response, with no cancer cells detected in the resected specimens. Severe postoperative complications occurred in five patients (20%), with one death. The disease recurred in five of the 18 patients who underwent a curative resection. A second primary tumor developed in two other patients. Seventeen patients (68%) are alive, with a median follow-up of 37 months after thoracotomy. The estimated three-year survival was 67% for all patients.

Angiotensin II-induced endothelium-dependent relaxation of fowl aorta

In the domestic fowl, angiotensin II (ANG II) decreases blood pressure in vivo and causes endothelium-dependent relaxation of aortic smooth muscles in vitro. To characterize ANG II-induced vasorelaxation, we compared endothelium-dependent vasodilatory effects of [Asp1,Val5]-ANG II (fowl ANG II) and acetylcholine (ACh) with the endothelium-independent vasorelaxing effect of sodium nitroprusside (SNP) on isometric tension of fowl aortic rings. Hemoglobin (Hb), gossypol, and N omega-nitro-L-arginine methyl ester (L-NAME), inhibitors for endothelium-derived relaxing factor (EDRF) in mammalian blood vessels, partially inhibited vasorelaxation induced by ANG II and ACh in fowl. Hb also markedly attenuated SNP-induced vasorelaxation, but not 8-bromoguanosine 3',5'-cyclic monophosphate-induced relaxation. 3,4,5-Trimethoxybenzoic acid 8-(diethylamino)octyl ester hydrochloride (TMB-8) or the removal of Ca2+ from the bathing medium attenuated the ACh-induced relaxation but did not significantly reduce vasorelaxation induced by ANG II or SNP. In the zero Ca2+ medium, aortic rings showed tachyphylaxis to ACh, while ANG II caused tachyphylaxis regardless of the presence or absence of external Ca2+. Furthermore, pretreatment of the ring with a high dose of ACh abolished the vasorelaxation response to ANG II, suggesting that ACh and ANG II may share a common Ca2+ pool. Calmidazolium, a calmodulin antagonist, abolished the vasorelaxation induced by ANG II and ACh but not that by SNP. Comparison of the vasodilatory effects of several ANG II analogues on fowl aortic rings showed an approximate potency order of [Asp1,Val5]-ANG II = [Asp1,Ile5]-ANG II > [Asn1,Ile5]-ANG II = [Sar1,Ile5]-ANG II > [Val5]-ANG III.(ABSTRACT TRUNCATED AT 250 WORDS)

Haemodynamic and neurohumoral changes in spontaneously hypertensive rats with aortocaval fistulae

1. Our aim was to evaluate the effects of an aortocaval fistula (1 mm) on cardiorenal haemodynamics, cardiac hypertrophy and neurohumoral factors in spontaneously hypertensive rats and to compare the results with those observed in Wistar rats at 2 weeks after fistulae placement. Sham-operated spontaneously hypertensive rats and Wistar rats served as controls. 2. Heart weight was significantly increased in spontaneously hypertensive rats (34%) and in Wistar rats (43%) at 2 weeks after fistula creation. Left ventricular systolic pressure and dp/dtmax. were significantly decreased (both P < 0.01) in spontaneously hypertensive rats with fistulae which had higher left ventricular end-diastolic pressure than Wistar rats with fistulae (P < 0.01). Signs of circulatory congestion (ascites, tachypnoea, prostration) were observed only in the overloaded spontaneously hypertensive rats (45%). Cardiac index was comparably increased in both fistulae groups due to an increase in stroke index, since heart rate was not increased. 3. Fistulae placement decreased renal blood flow and kidney weight, and increased blood urea nitrogen to a greater degree in spontaneously hypertensive rats (all P < 0.05); serum creatinine levels were unaltered. Plasma noradrenaline concentration was increased in spontaneously hypertensive rats with fistulae (P < 0.05), whereas plasma renin activity was not changed. 4. Thus, spontaneously hypertensive rats with fistulae developed overt haemodynamic signs of high-output heart failure with frequent ascites and dyspnoea, whereas most of these findings were milder or absent in Wistar rats. This model provides an opportunity to evaluate the pathophysiological and pharmacological responses in high-output heart failure.

Hemodynamic and neurohumoral responses to exercise in patients with congestive heart failure

Hemodynamic and neurohumoral responses to supine bicycle exercise were evaluated in 16 patients with congestive heart failure (New York Heart Association functional class II-III) and in 8 normal controls. We determined cardiac output by the dye-dilution method, and forearm hemodynamics by plethysmography. The patients had lower resting cardiac and stroke indexes (p < 0.05) than the normal controls. During exercise, the increase in the cardiac index due to an increase in heart rate, was less than that in the controls. Resting and exercise systemic vascular resistance indices were higher in the patients (p < 0.05). The patients had lower resting forearm blood flow and higher forearm vascular resistance (p < 0.05), and the increases during exercise were comparable in the 2 groups. However, forearm venous tone and venous pressure increased more in the patients (p < 0.05). Exercise duration was shorter in the patients (p < 0.01). Resting plasma angiotensin II and norepinephrine were similar in the 2 groups, but plasma 6-keto-prostaglandin F1 alpha and atrial natriuretic peptide were higher in the patients. During exercise, all of these neurohumoral parameters rose more in the patients than in the controls (p < 0.05). Thus, the patients exhibited impaired central and peripheral hemodynamics both at rest and during exercise. The excessive exercise responses of all of the neurohumoral factors suggest that both vasoconstrictor and vasodilator systems are activated in heart failure.

Kinetics of GLUT1 and GLUT4 glucose transporters expressed in Xenopus oocytes

The predominant mechanism by which insulin activates glucose transport in muscle and adipose tissue is by affecting the redistribution of the facilitated hexose carriers, GLUT1 and GLUT4, from an intracellular site to the plasma membrane. A quantitative analysis of this process has been hampered by the lack of reliable determinations for kinetic constants catalyzed by each of these isoforms. In order to obtain such information, each transporter was expressed in Xenopus oocytes by the injection of mRNA encoding rat GLUT1 or GLUT4. Equilibrium exchange 3-O-methylglucose uptake was measured and the data fitted to a two-compartment model, yielding Km = 26.2 mM and Vmax = 3.5 nmol/min/cell for GLUT1 and Km = 4.3 mM and Vmax = 0.7 nmol/min/cell for GLUT4. Measurement of the abundance of cell surface transporters was accomplished by two independent protocols: photolabeling with the impermeant hexose analog 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2-propylamine and subcellular fractionation of oocytes. Data obtained by either technique revealed that the ratio of plasma membrane GLUT1 to GLUT4 was about 4; this paralleled the relative maximal velocities for hexose transport, indicating that the turn-over numbers for the two isoforms were the same. Moreover, measurement of the concentration of exofacially disposed transporters with 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2-propylamine allowed calculation of the turnover number to be about 20,000 min-1. These data indicate that, at low substrate concentrations, the catalytic efficiency of GLUT4 is significantly greater than GLUT1. Extrapolation to mammalian systems suggests that GLUT4 is responsible for virtually all of the hexose uptake in insulin-responsive targets, particularly in the presence of hormone.

Are diabetic hearts more resistant to ischemia/reperfusion injury?

The present study was designed to investigate the cardiac impairment during ischemia/reperfusion injury in rats with streptozotocin-induced diabetes vs controls. Male rats were divided into three groups: controls, one-week diabetic rats (1wDM) and four-week diabetic rats (4wDM). In the isolated working heart, left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), and maximum positive and negative dP/dt were measured before ischemia and after 20 min of global ischemia followed by 30 min reperfusion. In the pre-ischemic state, hearts of 4wDM showed a significant (p < 0.05) depression of the maximum positive and negative dP/dt compared with those of controls and 1wDM. There were no significant differences in LVDP and LVEDP among the three groups. The incidence of reperfusion-induced ventricular fibrillation (VF) was 75% for controls, 15% for 1wDM rats, and 27% for 4wDM rats. In hearts without reperfusion-induced VF, there were no differences in the three groups, between the pre- and post-ischemic values in LVDP, LVEDP, and maximum positive and negative dP/dt. These findings suggest that diabetic hearts exhibit no susceptibility to ischemia/reperfusion injury.