bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of sodium transport mediates regulation of thyroid follicle volume in response to hypotonic media
Authors: Yap A. S. , Armstrong J. W. , Cragoe E. J. , Bourke J. R. , Huxham G. J. , Manley S. W.
Published: December 2017

The thyroid epithelium possesses a bidirectional fluid transport system capable of absorbing Na+ and secreting Cl-. In the present studies we have examined its possible role in the regulation of thyroid follicular size. When exposed to hypotonic media (200 mosM) cultured porcine thyroid follicles first swelled and then displayed a regulatory volume decrease (RVD) over 60 min. This was associated with a transient depolarization of the transepithelial potential difference (TEP) and subsequent hyperpolarization with a time course similar to RVD. Phenamil (1 microM), an antagonist of epithelial Na+ channels, did not affect initial swelling but prevented the subsequent follicular RVD. Phenamil abolished hyperpolarization of TEP, but the loop diuretic bumetanide, which inhibits Cl- secretion in thyroid cells, did not prevent it. Exposure to hypotonic medium produced a slow hyperpolarization of the intracellular potential (basolateral membrane potential) consistent with an increase in basolateral membrane K+ conductance. Ba2+ and quinidine, which are known to inhibit K+ channels in epithelia, prevented RVD. Addition of the K+ ionophore valinomycin (1 microM) caused follicle shrinkage that was prevented by phenamil (1 microM). We conclude that cultured follicles respond to hypotonically induced stretch by activating outwardly directed Na+ transport through a mechanism which involves change in the basolateral K+ conductance. This response would be characteristic of a system that controlled follicle volume. However, it is not clear from these studies whether the cells responded primarily to the increase in follicle volume or to the change in cell volume that is expected to accompany hypotonic challenge.
Glucocorticoids activate the ATP-ubiquitin-dependent proteolytic system in skeletal muscle during fasting
Authors: Wing S. S. , Goldberg A. L.
Published: December 2017

Glucocorticoids are essential for the increase in protein breakdown in skeletal muscle normally seen during fasting. To determine which proteolytic pathway(s) are activated upon fasting, leg muscles from fed and fasted normal rats were incubated under conditions that block or activate different proteolytic systems. After food deprivation (1 day), the nonlysosomal ATP-dependent process increased by 250%, as shown in experiments involving depletion of muscle ATP. Also, the maximal capacity of the lysosomal process increased 60-100%, but no changes occurred in the Ca(2+)-dependent or the residual energy-independent proteolytic processes. In muscles from fasted normal and adrenalectomized (ADX) rats, the protein breakdown sensitive to inhibitors of the lysosomal or Ca(2+)-dependent pathways did not differ. However, the ATP-dependent process was 30% slower in muscles from fasted ADX rats. Administering dexamethasone to these animals or incubating their muscles with dexamethasone reversed this defect. During fasting, when the ATP-dependent process rises, muscles show a two- to threefold increase in levels of ubiquitin (Ub) mRNA. However, muscles of ADX animals failed to show this response. Injecting dexamethasone into the fasted ADX animals increased muscle Ub mRNA within 6 h. Thus glucocorticoids activate the ATP-Ub-dependent proteolytic pathway in fasting apparently by enhancing the expression of components of this system such as Ub.
Acute fasting is ineffective in suppressing pituitary-gonadal function of pubertal male rats
Authors: Bergendahl M. , Huhtaniemi I.
Published: December 2017

Effects of short-term fasting (3–4 days) on pituitary-testicular functions were studied during sexual maturation in male rats at 25, 35, 45, 55, and 65 days of age. Among the main findings, testicular testosterone decreased by 41–68% at all ages (P < 0.01–0.05). The pituitary steady-state mRNA levels of the common alpha-subunit (28–55%) and follicle-stimulating hormone (FSH) beta-subunit (25–50%) decreased (P < 0.01–0.05) at 25, 55, and 65 days of age but not at 35 and 45 days; the luteinizing hormone (LH) beta-subunit did not respond at any age. Fasting decreased serum LH (P < 0.01) at 25, 55, and 65 days of age but not at 35 and 45 days. Likewise, fasting decreased pituitary and/or serum FSH only in the 25- and 65-day-old rats (P < 0.01–0.05). In conclusion, LH and FSH secretion, and the gene expression of common alpha- and FSH beta-subunits, decreased consistently during short-term fasting only in prepubertal (25 days) and adult (65 days) but not in peripubertal animals (35 and 45 days). Hence, the pubertal rise in gonadotropins represents such a strong positive induction that it largely overrides the antigonadotropic effect of fasting.
Catabolism of cysteine, cystine, cysteinesulfinate, and OTC by isolated perfused rat hindquarter
Authors: Ensunsa J. L. , Hirschberger L. L. , Stipanuk M. H.
Published: December 2017

The metabolism of cysteine and related compounds was investigated in the isolated perfused hindquarter of the rat. An erythrocyte-based perfusion medium was used; use of a perfluorochemical emulsion, FC-43, resulted in apparent chemical oxidation of cysteine, whereas bovine erythrocytes did not appear to contribute significantly to the metabolism of cysteine. Rat skeletal muscle perfused with L-[35S]cysteine, L-[35S]cystine, L-[35S]cysteinesulfinate, or L-2-oxo-[35S]thiazolidine-4-carboxylate (OTC) for 2 h produced [35S]sulfate and [35S]taurine. In all cases, the partitioning of cysteine or cysteinesulfinate between metabolism to taurine and sulfate was similar, suggesting that cysteine metabolism in hindquarter may occur via formation and catabolism of cysteinesulfinate by either cysteinesulfinate decarboxylase or aspartate (cysteine-sulfinate) aminotransferase. However, the activity of cysteine dioxygenase was extremely low, suggesting that the conversion of cysteine to cysteinesulfinate may have been non-enzymatic.
Response of rat heart and skeletal muscle protein in vivo to insulin and amino acid infusion
Authors: McNulty P. H. , Young L. H. , Barrett E. J.
Published: December 2017

Whether insulin, at physiological concentrations, stimulates net muscle protein synthesis in vivo remains unresolved. To examine this, we infused either saline, insulin (2.8 mU.kg-1.min-1, euglycemic clamp), an amino acid solution, or insulin plus amino acids for 4 h into awake overnight-fasted rats. Heart and skeletal muscle protein synthesis was measured by either a continuous tracer infusion method, using L-[1-14C]leucine, L-[2,5-3H]leucine, or L-[ring-2,6-3H]phenylalanine or by injection of L-[ring-2,6-3H]phenylalanine with a pool-flooding bolus of unlabeled phenylalanine. In heart, synthesis rates obtained using the arterial plasma specific activity of [3H]phenylalanine administered as either a tracer infusion or flooding bolus were comparable in saline-treated rats (range 10.9 +/- 1.2 to 12.2 +/- 0.9%/day) and were not affected by infusion of insulin or amino acids. Estimates using continuous infusion of L-[1-14C]leucine were significantly lower (P < 0.001), except when unlabeled amino acids were given also. In skeletal muscle, rates estimated using the flooding bolus (6.7 +/- 0.8%/day) were also not affected by insulin or amino acids. Estimates using continuous infusion of [3H]leucine (2.6 +/- 0.3%/day) or [3H]phenylalanine (2.8 +/- 1.0%/day) were lower and were still lower using [14C]leucine (1.6 +/- 0.6%/day), but increased toward those estimated with the flooding bolus during amino acid infusion. We conclude that, in heart muscle of the mature rat in vivo, neither insulin nor amino acids affect protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Glutamine transport in human skeletal muscle
Authors: Ahmed A. , Maxwell D. L. , Taylor P. M. , Rennie M. J.
Published: December 2017

Sarcolemmal vesicles isolated from human skeletal muscle obtained at surgery showed approximately 14-fold enrichment of sarcolemmal marker enzymes 5'-nucleotidase and K-stimulated phosphatase. [3H]glutamine transport in these vesicles was stereospecific, largely Na dependent, and tolerated Li-for-Na substitution. Glutamine transport was stimulated by an inside negative membrane potential, and 25 mM glutamine stimulated 22Na (0.1 mM) uptake into vesicles by 50%, indicating rheogenic cotransport of Na and glutamine. Alanine transport was Na dependent but did not tolerate Li-for-Na substitution. Transport of L-[3H]glutamine was inhibited by 35-65% with a 20-fold excess of glutamine, asparagine, and alanine; cysteine, alpha-(methylamino)isobutyrate, and 2-amino-2-norborane carboxylic acid had smaller inhibitory effects, although cysteine had an unusually large inhibitory effect on glutamine transport at 1,000-fold excess compared with most other amino acids. Glutamine transport showed sensitivity to pH values < 7.0. Glutamine transport consisted of a Na-dependent and a Na-independent component, both of which appeared saturable. The kinetic characteristics of the Na-dependent component were different in different types of muscles, with half-maximal concentrations (mM) varying from 1.6 +/- 0.4 (tibialis anterior) to 0.56 +/- 0.0.2 (gluteus maximus) and maximal velocity (pmol.mg protein-1.s-1) of 1.3 +/- 0.27 to 5 +/- 1.25 in the same muscles. The results demonstrate both marked similarities and important differences between the principal glutamine transporter in human skeletal muscle and the known system Nm transporter in rat skeletal muscle.
Leucine metabolism in lactating and dry goats: effect of insulin and substrate availability
Authors: Tesseraud S. , Grizard J. , Debras E. , Papet I. , Bonnet Y. , Bayle G. , Champredon C.
Published: December 2017

Early lactating goats show insulin resistance with respect to extramammary glucose utilization. However, much less is known about the two major factors, insulin and plasma amino acid concentration, that regulate protein metabolism in lactating goats. To examine this question, the in vivo effect of acute insulin was studied in goats during early lactation (12-31 days postpartum), midlactation (98-143 days postpartum), and the dry period (approximately 1 yr postpartum). Insulin was infused (at 0.36 or 1.79 nmol/min) under euglycemic and eukaliemic clamps. In addition, appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidemia or to create hyperaminoacidemia and maintain this condition under insulin treatment. Leucine kinetics were assessed using a primed continuous infusion of L-[1-14C]-leucine, which started 2.5 h before insulin. In all animals the insulin treatments failed to stimulate the nonoxidative leucine disposal (an estimate of whole body protein synthesis) under both euaminoacidemic and hyperaminoacidemic conditions. Thus, in goat as well as humans, infusion of insulin fails to stimulate protein synthesis even when combined with a substantially increased provision of amino acids. In contrast, insulin treatments caused a dose-dependent inhibition of the endogenous leucine appearance (an estimate of whole body protein degradation). Under euaminoacidemia the initial slope from the plot of the endogenous leucine appearance as a function of plasma insulin (an insulin sensitivity index) was steeper during early lactation than when compared with the dry period. A similar trend occurred during midlactation but not to any significant degree. These differences were abolished under hyperaminoacidemia. It was concluded that the ability of physiological insulin to inhibit protein degradation was improved during lactation, demonstrating a clear-cut dissociation between the effects of insulin on protein and glucose metabolism. This adaptation no doubt may provide a mechanism to save body protein.
Effects of blockade of fatty acid oxidation on whole body and tissue-specific glucose metabolism in rats
Authors: Jenkins A. B. , Storlien L. H. , Cooney G. J. , Denyer G. S. , Caterson I. D. , Kraegen E. W.
Published: December 2017

We examined the effect of the long-chain fatty acid oxidation blocker methyl palmoxirate (methyl 2-tetradecyloxiranecarboxylate, McN-3716) on glucose metabolism in conscious rats. Fasted animals [5 h with or without hyperinsulinemia (100 mU/l) and 24 h] received methyl palmoxirate (30 or 100 mg/kg body wt po) or vehicle 30 min before a euglycemic glucose clamp. Whole body and tissue-specific glucose metabolism were calculated from 2-deoxy-[3H]-glucose kinetics and accumulation. Oxidative metabolism was assessed by respiratory gas exchange in 24-h fasted animals. Pyruvate dehydrogenase complex activation was determined in selected tissues. Methyl palmoxirate suppressed whole body lipid oxidation by 40-50% in 24-h fasted animals, whereas carbohydrate oxidation was stimulated 8- to 10-fold. Whole body glucose utilization was not significantly affected by methyl palmoxirate under any conditions; hepatic glucose output was suppressed only in the predominantly gluconeogenic 24-h fasted animals. Methyl palmoxirate stimulated glucose uptake in heart in 24-h fasted animals [15 +/- 5 vs. 220 +/- 28 (SE) mumol x 100 g-1 x min-1], with smaller effects in 5-h fasted animals with or without hyperinsulinemia. Methyl palmoxirate induced significant activation of pyruvate dehydrogenase in heart in the basal state, but not during hyperinsulinemia. In skeletal muscles, methyl palmoxirate suppressed glucose utilization in the basal state but had no effect during hyperinsulinemia; pyruvate dehydrogenase activation in skeletal muscle was not affected by methyl palmoxirate under any conditions. The responses in skeletal muscle are consistent with the operation of a mechanism similar to the Pasteur effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Importance of transcapillary insulin transport to dynamics of insulin action after intravenous glucose
Authors: Yang Y. J. , Hope I. D. , Ader M. , Bergman R. N.
Published: December 2017

Insulin action in vivo is determined by both transendothelial insulin transport (TET) across the capillary and subsequent insulin binding and postreceptor events. To examine TET under non-steady-state conditions, we performed intravenous glucose tolerance tests (IVGTT; 0.3 g/kg; n = 7) on conscious dogs. At basal, insulin in lymph was only 53 +/- 7% of plasma insulin (P < 0.001), whereas lymph glucose exceeded plasma levels (109 +/- 4 vs. 104 +/- 4 mg/dl, respectively; P < 0.02). On injection, dynamics of glucose in plasma and lymph were similar, suggesting rapid equilibration of glucose between compartments. In contrast, insulin appearance in lymph was delayed relative to plasma (5.1 +/- 1.3 vs. 2 +/- 0 min), peaked later (21 +/- 2 vs. 8 +/- 2 min), attained peak value of only 52 +/- 6% of plasma insulin (range, 35-76%), and remained lower than plasma insulin throughout the IVGTT (P < 0.05 or better). Minimal model-derived insulin sensitivity (SI) averaged 3.55 +/- 0.75 x 10(-4) min-1/(microU/ml). There was a strong linear relationship between lymph insulin and its effect on glucose disappearance [X(t), r = 0.95 +/- 0.01]. Determination of the relative contributions of TET and post-TET insulin-sensitive processes to overall SI revealed that cellular sensitivity to interstitial insulin dominated (r2 = 0.55), but was not the exclusive determinant of, overall SI, as insulin transport was also important (r2 = 0.21). TET is a previously unrecognized contributor to SI in vivo.
Blood-brain barrier transport of neuropeptides: analysis with a metabolically stable dermorphin analogue
Authors: Samii A. , Bickel U. , Stroth U. , Pardridge W. M.
Published: December 2017

To avoid the confounding effect of metabolic degradation, the stable mu-opioid peptide agonist [D-Arg2,Lys4]-dermorphin analogue (DALDA) was used to quantitate blood-brain barrier (BBB) permeability by intravenous injection and internal carotid artery perfusion techniques. With intravenous injection, the BBB permeability-surface area products for [3H]DALDA (0.84 +/- 0.13 microliters.min-1.g-1) and [14C]sucrose (0.39 +/- 0.05 microliters.min-1.g-1) correlated with the lipid solubility of the two molecules: the 1-octanol-Ringer partition coefficient for DALDA was approximately 2 log orders greater than that for sucrose. The brain delivery of [3H]DALDA at 30 min after intravenous administration was 0.019 +/- 0.002% of the injected dose per gram, and analgesia was induced with a 5-mg/kg dose administered systemically. In contrast to the result after intravenous injection, the BBB permeability-surface area product for DALDA estimated with the internal carotid artery perfusion technique was manyfold greater. This was due to nonspecific absorption of the peptide into the cerebral microvasculature, which precluded use of the capillary depletion technique to study transcytosis through the BBB after internal carotid artery perfusion. The present studies show that the brain delivery of a metabolically stable peptide, such as DALDA, is comparable to that for sucrose, correlates with lipid solubility, and is mediated by a nonsaturable mechanism, probably free diffusion.
Immunohistochemical localization of the 1,25(OH)2D3 receptor and calbindin D28k in human and rat pancreas
Authors: Johnson J. A. , Grande J. P. , Roche P. C. , Kumar R.
Published: December 2017

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] is required for normal glucose-stimulated insulin release from pancreatic beta-cells. Biochemical characterization techniques have demonstrated the presence of the 1,25(OH)2D3 receptor (VDR) in homogenates of whole pancreas. Autoradiographic studies using radiolabeled 1,25(OH)2D3 suggest that the VDR is localized to beta-cells but are inconclusive. We used immunohistochemical techniques to stain serial sections from both human and rat pancreas with polyclonal antibodies to human VDR, chick calbindin D28k, insulin, glucagon, and somatostatin. VDR was present in the islet cells and also at low levels in acinar cells of the human and rat pancreas. Calbindin D28k was distributed in a manner similar to the VDR in pancreatic islets but was not present in acini. These results show for the first time that VDR and calbindin D28k are present in human pancreatic tissue. VDR and calbindin D28k are focally distributed throughout pancreatic islet cell types in humans and rats; VDR is also present in the exocrine pancreas. These findings suggest that 1,25(OH)2D3 may influence both endocrine and exocrine pancreatic function.
Whole body protein synthesis in healthy adult humans: 13CO2 technique vs. plasma precursor approach
Authors: el-Khoury A. E. , Sanchez M. , Fukagawa N. K. , Young V. R.
Published: December 2017

Different methods for the estimation of whole body protein synthesis (PS) in healthy adult humans were simultaneously compared in seven young adult subjects (6 males, 1 female) fed for 6 days a diet providing 1 g protein.kg-1.day-1 and approximately 188 kJ.kg-1.day-1. A 24-h intravenous tracer study with L-[1-13C]leucine was performed starting at 6 P.M. on day 6. During fasted (6 h) and fed (6 h) steady states, PS was estimated using an approach based on 13CO2 excretion (PSexcr) and on urinary nitrogen excretion data (corrected for changes in body urea pool). Simultaneously, we used the conventional two-pool model and plasma [13C]ketoisocaproate enrichment for estimating PS. The latter mean estimates of PS were significantly higher than PSexcr during fasting [861 +/- 58 (SD) vs. 663 +/- 160 mg protein.kg-1.6 h-1; P < 0.01] and feeding (985 +/- 63 vs. 779 +/- 127 mg protein.kg-1.6 h-1; P < 0.01) and were much less variable. In hourly small-meal feeding, urinary nitrogen excretion was not a reliable index of body protein oxidation when measured over short periods of 6 h, thereby introducing a lack of precision in PSexcr. We suggest that application of the 13CO2 technique to measure PS in humans is limited by the need for relatively prolonged experimental periods of urine collection and tracer infusion within a given physiological state.
Transmembrane transport and intracellular kinetics of amino acids in human skeletal muscle
Authors: Biolo G. , Fleming R. Y. , Maggi S. P. , Wolfe R. R.
Published: December 2017

We have used stable isotopic tracers of amino acids to measure in vivo transmembrane transport of phenylalanine, leucine, lysine, alanine, and glutamine as well as the rates of intracellular amino acid appearance from proteolysis, de novo synthesis, and disappearance to protein synthesis in human skeletal muscle. Calculations were based on data obtained by the arteriovenous catheterization of the femoral vessels and muscle biopsy. We found that the fractional contribution of transport from the bloodstream to the total intracellular amino acid appearance depends on the individual amino acid, varying between 0.63 +/- 0.02 for phenylalanine and 0.22 +/- 0.02 for alanine. Rates of alanine and glutamine de novo synthesis were approximately eight and five times their rate of appearance from protein breakdown, respectively. The model-derived rate of protein synthesis was highly correlated with the same value calculated by means of the tracer incorporation technique. Furthermore, amino acid transport rates were in the range expected from literature values. Consequently, we conclude that our new model provides a valid means of quantifying the important aspects of protein synthesis, breakdown, and amino acid transport in human subjects.
Role of adenosine in noradrenergic neurotransmission
Authors: Kuan C. J. , Jackson E. K.
Published: December 2017

The purpose of this study was to evaluate the hypothesis that endogenous adenosine modulates noradrenergic neurotransmission in vivo during sustained periods of sympathetic nerve stimulation associated with a reduction in tissue blood flow. This hypothesis was tested in the rat mesentery in vivo by comparing the effects of periarterial (sympathetic) nerve stimulation (PNS) on mesenteric blood flow and norepinephrine (NE) spillover from the mesentery in control rats vs. rats treated with the adenosine receptor antagonist 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX; 10 mg + 150 micrograms/min iv). In both control rats and rats pretreated with DPSPX, sustained PNS (7 Hz for 30 min) caused an initial large decrease in mesenteric blood flow and increase in NE spillover; however, these responses attenuated over the 30-min stimulation period. The time course of PNS-induced changes in mesenteric blood flow and NE spillover were not altered by treatment with DPSPX. However, administration of DPSPX prevented inhibition of noradrenergic neurotransmission in the rat mesentery by 2-chloroadenosine, which indicated that an effective level of DPSPX was achieved. We conclude that even during sustained sympathetic nerve stimulation associated with reductions in tissue perfusion, endogenous adenosine does not modulate noradrenergic neurotransmission in vivo in the rat mesentery.
Accuracy of volume measurement of rabbit left ventricle by balloon method
Authors: Goto Y. , Slinker B. K. , LeWinter M. M.
Published: December 2017

Although the intraventricular balloon method has been commonly used to measure left ventricular volume of the isolated heart preparation of various animals, the accuracy of the method has not been examined in the ventricle of small animals such as the rabbit. To assess the accuracy of the intraventricular balloon method in measuring left ventricular volume, we measured the space between the balloon inflated in the left ventricle and the endocardial surface in eight Formalin-fixed rabbit left ventricles. The space was only 0.05–0.12 ml (1.5–3.6% of total left ventricular volume) at intraballoon pressures of 40–160 mmHg. However, it increased to 0.37 ml (14.6% of total ventricular volume) with a decrease in pressure to 5 mmHg. We conclude that the intraventricular balloon method accurately measures left ventricular volume in the rabbit, especially in the high pressure range.
Support of arterial blood pressure by major pressor systems in conscious dogs
Authors: Brand P. H. , Metting P. J. , Britton S. L.
Published: December 2017

The roles of the autonomic nervous system, vasopressin, and angiotensin II in support of blood pressure were evaluated in seven conscious, resting dogs while hydrated or dehydrated. Mean arterial blood pressure (MAP) was monitored, and the dogs were given hexamethonium to block autonomic ganglia. Thirty minutes later, they were given captopril, and after another 30 min, a vasopressin V1 antagonist, d(CH2)5TyrMeAVP, was given. The order okf administration of captopril and d(CH2)5TyrMeAVP was alternated in different experiments. Hexamethonium had no effect on steady-state MAP in either hydrated or dehydrated dogs. In hydrated dogs, the average MAP was 100 mmHg; d(CH2)5TyrMeAVP decreased MAP by approximately 12 mmHg, and captopril decreased MAP by 24 mmHg. The magnitude of the effect of these two inhibitors was independent of the order of their administration. Dehydration doubled the effect of d(CH2)5TyrMeAVP on MAP but had no effect on the response to captopril. The results suggest that 1) autonomic function is not essential for maintenance of arterial blood pressure in resting dogs; 2) during autonomic ganglionic blockade, arterial blood pressure is supported by both angiotensin II and vasopressin; and 3) dehydration increases the role of vasopressin in control of blood pressure.
Adenosine and hypoxia stimulate proliferation and migration of endothelial cells
Authors: Meininger C. J. , Schelling M. E. , Granger H. J.
Published: December 2017

The proliferation of bovine aortic or coronary venular endothelial cells (EC) in vitro was stimulated by the addition of adenosine (0.5 or 5.0 microM) to the culture medium. Cell counts of adenosine-treated aortic EC were 23–76% and coronary venular EC 19–52% greater than nontreated controls. Because adenosine is known to be released by hypoxic tissues, cell proliferation was quantitated when aortic EC were grown at 2% O2. Cell counts were 41–102% greater under hypoxic conditions than when cells were grown at standard tissue culture conditions (approximately 20% O2). When culture medium conditioned by coronary EC grown at 2% O2 was added to EC growing at standard conditions, cell counts were 24–69% greater than controls with medium conditioned by coronary EC grown at 20% O2. This suggests that hypoxia causes endothelial cells to release a factor(s) into the medium that can stimulate cell proliferation. The addition of the adenosine receptor blocker 8-phenyltheophylline (10(-5) M) prevented the stimulation of proliferation caused by hypoxia-conditioned medium, 2% O2 or 5.0 microM adenosine, suggesting that adenosine mediates its effect via an external membrane receptor. Adenosine also stimulated EC chemotaxis. Taken together, these results suggest that adenosine, released as a result of tissue hypoxia, may act as an angiogenic stimulus for the growth of new blood vessels.
Evaluation of right and left ventricular size in SHR-Wistar hybrids
Authors: Grassi de Gende A. O.
Published: December 2017

The relative right and left ventricular sizes were evaluated in hybrid rats obtained by crossing spontaneously hypertensive (SHR) and pure Wistar strains to detect cardiac hypertrophy dissociated from the hypertension genetically transmitted by the SHR strain. In female hybrids of the the F1, F2, and F3 generations, both ventricles were found to have bigger size in relation to body weight than in the pure Wistar, whereas only the F3 group was hypertensive. All generations of male hybrids had arterial pressure values in the hypertensive range, which were not consistently accompanied by increases in the ventricle mass. The correlation between arterial pressure and indexes of ventricular size was assessed in sex-age matched groups. In a range of systolic pressure values of 100– 200 mmHg, the variables showed no correlation or poor positive correlation (correlation coefficient values from -0.3641 to 0.6153). The correlation was not improved in the F3 generation as would be expected, because these hybrids underwent higher left pressure load than the preceding generations. The results indicate that increased ventricular size in SHR-Wistar hybrids may be independent from the hypertension genetically transmitted by the SHR strain and suggest that some of the previously proposed factors, i.e., cardioadrenergic activity or the growth factor isolated from SHR hearts, may be playing a role in the ventricular hypertrophy process in this strain. If this characteristic of hybrids is a constant in pure SHR strain, its validity as a model of cardiac hypertrophy due to left pressure overload would be questioned.
Separation of cardiac myosin heavy chains by gradient SDS-PAGE
Authors: Esser K. A. , Boluyt M. O. , White T. P.
Published: December 2017

Separation of alpha- and beta-myosin heavy chains (MHCs) in cardiac ventricles of rats by gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was accomplished and compared with the separation of myosin isozymes obtained with pyrophosphate gels. Whole muscle homogenates were electrophoresed on a 4–9% linear gradient SDS polyacrylamide gel for 3–4 h. MHC bands were identified by the migration distance relative to a MHC standard and immunoblot results with a monoclonal antibody to MHC. The MHC bands were further identified as alpha and beta based on the electrophoretic mobility of ventricular homogenates from hypothyroid and hyperthyroid rats and ventricular and slow soleus skeletal muscle homogenates from control rats. The beta-MHC migrated faster than alpha-MHC, and laser densitometry revealed separate peaks when both MHCs were present. With homogenates containing MHC ranging from 0 to 100% alpha, the separation of MHCs with gradient SDS-PAGE correlated highly (r = 0.97) with separation of myosin isozymes by pyrophosphate gel electrophoresis. The SDS-PAGE technique reported herein is a quick, valid, and direct method for the identification and quantification of ventricular MHCs.
Inotropic sensitivity to beta-adrenergic stimulation in early sepsis
Authors: Smith L. W. , McDonough K. H.
Published: December 2017

In early sepsis, maintenance of in vivo cardiovascular performance is at least partly dependent on sympathetic support to hearts with intrinsic contractile defects. Yet prolonged sympathetic stimulation, as occurs in sepsis, would be expected to alter the heart's ability to respond to this stimulation. We have investigated myocardial inotropic sensitivity to beta-adrenergic stimulation in a model of sepsis in which animals, at the time studied, exhibited bacteremia, normal arterial blood pressure and cardiac output, elevated heart rate, and elevated plasma catecholamines. Intrinsic myocardial contractile function, as assessed by the maximal rate of left ventricular pressure development (LV dP/dtmax) in an isovolumically contracting heart preparation, was significantly depressed in septic animals. To determine whether hearts from septic animals could respond normally to beta-adrenergic stimulation, we studied inotropic response to a bolus of isoproterenol in these isolated hearts. With maximal isoproterenol stimulation, hearts from septic animals were able to attain the same dP/dtmax as were hearts from control animals. With lower levels of isoproterenol, there was also no difference in inotropic indexes between the two groups when response was expressed as a percent of the maximal increase in dP/dtmax achieved with isoproterenol. These results suggest that in early sepsis, despite intrinsic myocardial contractile dysfunction, the ability of the heart to modulate its inotropic state in response in beta-adrenergic stimulation is intact.
NE turnover in genetically hypertensive rats of Lyon strain. I. Brain nuclei
Authors: Sautel M. , Sacquet J. , Vincent M. , Sassard J.
Published: December 2017

Several indirect evidences of alterations in the central catecholaminergic structures were obtained in genetically hypertensive rats. Because they could be of pathogenetic value, we measured, in the present work, the in vivo turnover (TO) of norepinephrine (NE) in brain areas of 5- and 22-wk-old genetically hypertensive (LH) rats of the Lyon strain, and their simultaneously selected normotensive (LN) and low blood pressure (LL) controls. Among the changes observed, the increased TO of NE in the A2 and A6 regions of 5-wk-old LH rats and its decrease in the posteroventral hypothalamic nucleus of 22-wk-old LH animals appeared likely to compensate for hypertension. On the contrary, the decreased TO of NE in the anterior hypothalamic nucleus observed at 5 wk and in the A6 and A1 areas at 22 wk of age in LH rats could participate in the development or the maintenance of hypertension. Above all, it was postulated that the increased TO of NE found in the A7 region of 5-wk-old LH rats could play a primary role in the pathogenesis of hypertension in the Lyon model.
Cyclic AMP modulates Ca-activated K channel in cultured smooth muscle cells of rat aortas
Authors: Sadoshima J. , Akaike N. , Kanaide H. , Nakamura M.
Published: December 2017

Effects of adenosine 3',5'-cyclic monophosphate (cAMP) on single Ca-activated K current (IK(Ca)) in cultured smooth muscle cells of the rat aorta were investigated with the patch-clamp technique. In cell-attached patch configurations, extracellular application of isoproterenol (10(-5) M) increased the Ca-activated K currents. The increase in the currents was due to an increase in the probability of channel openings (Po). Neither unit conductance nor the maximum number of the channel in the patch was affected by the drug. The effects were inhibited by adding propranolol (10(-6) M). The extracellular application of forskolin (10(-5) M) or dibutyryl cAMP (10(-4) M) mimicked the effects of isoproterenol. In inside-out patch configurations, activated cAMP-dependent protein kinase (A kinase) in the bathing solution increased the sensitivity of the Ca-activated K channels to intracellular free calcium concentration ([Ca]i) and enhanced Po. Kinetic analyses of the IK(Ca) showed that cAMP-dependent phosphorylation of the Ca-activated K channels significantly reduced the mean closed time between bursting openings. We conclude from these observations that the Ca-activated K channels in aortic cells may increase Po through cAMP-dependent phosphorylation.
alpha-Adrenoceptors and cold-induced vasoconstriction in human finger skin
Authors: Ekenvall L. , Lindblad L. E. , Norbeck O. , Etzell B. M.
Published: December 2017

Experiments were designed to determine how cold-induced vasoconstriction is mediated in superficial vessels of human finger skin. alpha-Adrenoceptor antagonists were administered into the finger skin by iontophoresis, and local cooling was applied by a laser-Doppler probe supplied with Peltier elements. Cold-induced vasoconstriction was abolished after administration of the alpha 2-adrenoceptor antagonist rauwolscine but not after the alpha 1-adrenoceptor antagonist doxazosin. The results indicate that vasoconstriction on local cooling in human finger skin is mainly mediated by adrenoceptors of the alpha 2-subtype.
Intramural distribution of intestinal blood flow during sympathetic stimulation
Authors: Shepherd A. P. , Riedel G. L.
Published: December 2017

Recent studies indicate that the mucosal circulation of the small intestine possesses more potent local circulatory control mechanisms than the muscularis. Several lines of evidence support this assertion: the absence of reactive hyperemia in the muscularis, the confinement of glucose-induced hyperemia to the mucosal circulation, and the more effective autoregulation of villus blood flow in comparison with total blood flow. Therefore, we postulated that the mucosal circulation would exhibit a more pronounced ability to escape the vasoconstrictor influence of sympathetic nerve stimulation. To test this hypothesis, we used laser-Doppler velocimetry (LDV) to study the effects of perivascular nerve stimulation on blood flow in the muscularis and mucosa of isolated dog intestine. In two series of experiments, we measured total blood flow to a gut loop with an electromagnetic flow probe on the supply artery, while LDV measurements were made either on the mucosa or on the muscularis. Sympathetic stimulation (10 Hz) transiently reduced total blood flow to approximately 10% of control in both studies. Muscularis and mucosal blood flow both reached minimal values. Subsequently, total blood flow and the two regional perfusions exhibited "autoregulatory escape," but the propensity for blood flow to escape from sympathetic vasoconstriction was significantly greater in the mucosa than in the muscularis. These data provide more evidence that, compared with the muscularis, the intestinal mucosa possesses more potent local control mechanisms that oppose neurogenic vasoconstriction.
Substrate exchange in human limb muscle during exercise at reduced blood flow
Authors: Lundgren F. , Bennegard K. , Elander A. , Lundholm K. , Schersten T. , Bylund-Fellenius A. C.
Published: December 2017

The substrate exchange of the calf muscles during leg exercise was compared in patients with chronically reduced blood flow and in matched controls. The arteriovenous differences of glucose, lactate, pyruvate, free fatty acids, glycerol, acetoacetate, beta-OH-butyrate, oxygen, and carbon dioxide were analyzed at rest, at the end of two exercise periods at various work loads, and after 10 min of recovery. Calf blood flow was measured with an electrocardiogram-triggered, computerized, strain gauge, venous occlusion plethysmograph. The results indicate that there was increased extraction of oxygen and ketone bodies in patients with reduced blood flow during exercise, whereas the glucose extraction tended to be lower than in controls. The leg respiratory quotient was lower in the patients even at the point of claudicating pain, suggesting oxidation of endogenous fat. The simultaneously elevated lactate release can be explained by local hypoxia in some muscle fiber populations. The findings are discussed in relation to the enzymatic adaptations known to occur in the calf muscle tissue of these patients.
Pulmonary hypertension due to monocrotaline pyrrole is reduced by moderate thrombocytopenia
Authors: Ganey P. E. , Sprugel K. H. , White S. M. , Wagner J. G. , Roth R. A.
Published: December 2017

To elucidate further the role of the platelet in the development of monocrotaline pyrrole (MCTP)-induced lung injury and pulmonary hypertension, MCTP-treated rats were made thrombocytopenic by cotreatment with an anti-rat platelet serum (PAS). Lung injury was assessed from increases in lung weight, lavage fluid protein concentration, and lactate dehydrogenase activity and from accumulation in lung tissue of 125I-labeled albumin. These indexes of injury were not different in MCTP-treated rats with normal or reduced platelet numbers at day 4,8, or 14. In MCTP-treated rats not receiving the PAS, pulmonary arterial pressure was elevated by day 8. However, pulmonary arterial pressure was the same as controls at both day 8 and day 14 in MCTP-treated rats made moderately thrombocytopenic by cotreatment with PAS. More marked reduction of platelet number abolished the protective effect of thrombocytopenia against pulmonary hypertension. In a separate series of experiments, treatment with antibodies to platelet-derived growth factor (PDGF), a potential mediator in the response to MCTP-induced injury, did not protect rats from the cardiopulmonary effects of MCTP. These data indicate that moderate reduction of the number of circulating platelets prevents MCTP-induced pulmonary hypertension but not MCTP-induced lung injury, suggesting that the platelet is involved in the pulmonary hypertensive response to MCTP-induced lung injury by unknown mechanisms.
Regionally variable pulmonary artery responses to C3a
Authors: Crowell R. E. , Reed W. P. , Van Epps D. , Anaya T. , Chenoweth D. E. , Leach J. , Chick T. W.
Published: December 2017

Products of the complement (C) cascade may have direct effects on pulmonary vascular tissue and contribute to pulmonary vasoconstriction in states of C activation. We studied the effects of C3a, a C-derived vasoactive peptide, on isolated rabbit hilar (HPA) and main pulmonary arteries (MPA). C3a elicited concentration-dependent constriction of HPA (10(7) M to 5 x 10(7) M) but minimal response in MPA at all concentrations tested. The difference between HPA and MPA responses was significant (P less than 0.05, paired t test). To evaluate HPA desensitization to C3a, the peptide was reapplied at 60 min in some tissues and at 120 min in others. All tissues consistently exhibited less constriction at 60 min than observed with previous exposures. Histamine contribution to the HPA response to C3a was determined by exposing the tissues for 30 min before C3a application to pyrilamine (1 x 10(-5) M), an histamine H1-receptor antagonist. Pyrilamine reduced the HPA response to C3a by 70-85%. We conclude that 1) isolated rabbit PA responses exhibit regional variability to C3a over a range of concentrations; 2) C3a desensitizes HPA for at least 60 min, but the tissue demonstrates variable recovery within 120 min; and 3) HPA responses to C3a are reduced by pyrilamine, an H1-receptor antagonist.
Endogenous opiate modulation of baroreflexes in normotensive and hypertensive rats
Authors: Szilagyi J. E.
Published: December 2017

It is evident that hypertension is associated with elevated endogenous opiates. This study was designed to examine the role of endogenous opiates in the development and/or maintenance of two-kidney renovascular hypertension and in baroreceptor reflex function in conscious hypertensive rats. Naloxone administration during the onset of hypertension significantly attenuated the rise in blood pressure. After one week, systolic blood pressure in naloxone-treated rats was 27 mmHg lower than in 0.9% NaCl-treated hypertensive rats. Acute naloxone infusions in chronic hypertensive animals also significantly lowered blood pressure (-10%) and heart rate (-26%). Baroreceptor function was significantly enhanced in both normotensive (+135%) and hypertensive (+207%) rats after administration of naloxone. Furthermore, naloxone treatment also caused the baroreflex response to shift from the higher reset state toward that seen in normotensive counterparts. The inability of naloxone methyl bromide to alter baroreflex sensitivity indicates that the site(s) of action of opiates resides in the brain. These data support a role for opiates in the development and/or maintenance of renovascular hypertension, which may be related to alterations in baroreceptor reflex function.
Myocardial metabolism and coronary flow: effects of endotoxemia
Authors: Rumsey W. L. , Kilpatrick L. , Wilson D. F. , Erecinska M.
Published: December 2017

The effects of sublethal endotoxemia on the regulation of coronary flow by myocardial metabolism were examined in the isolated perfused heart preparation. Fasted Sprague-Dawley rats were injected (ip) with either endotoxin (0.5 mg/kg of body wt) or 5% dextrose 12 h before heart perfusion. The efficacy of endotoxin treatment was determined by measurement of plasma [NH3] and [urea] and colonic temperature. During perfusion with buffer containing glucose-pyruvate, oxygen consumption and coronary flow were increased by 17 and 42%, respectively, in hearts from endotoxin-treated rats as compared with those from controls. In the hearts from endotoxemic animals, the mitochondrial [NAD+]/[NADH] was decreased by approximately 25%, and the active form of pyruvate dehydrogenase was increased by 36% as compared with control hearts. [ATP]f/[ADP]f[Pi] was unaltered. The enhanced metabolic rate was associated with comparable changes in peak systolic pressure development, maximal positive and negative dP/dt, and the tension-time index when measured in the isovolumetric preparation. In these hearts, stimulation of respiration by perfusion with an alternate source of fuel or inhibition by infusion of amytal elicited large, transient increases in the level of coronary flow that returned rapidly to prestimulus values. By contrast, in hearts from controls, the transient increase in flow was coupled to sustained vasodilation, i.e., approximately 30% rise in flow for either metabolic condition. In both groups, [ATP]f/[ADP]f[Pi] either increased or decreased with stimulation or inhibition of respiration, respectively. Adenosine (1.2 microM) produced a 35% increase in flow in the hearts from the control animals, whereas it was without significant effect in those from the endotoxin-treated animals. It is concluded that sublethal endotoxemia causes 1) an increased metabolic rate and enhanced mechanical activity in the heart and 2) an uncoupling of flow from regulation by cardiac metabolism.
Carotid sinus baroreceptor control of splanchnic resistance and capacity
Authors: Brunner M. J. , Greene A. S. , Frankle A. E. , Shoukas A. A.
Published: December 2017

The contribution of the splanchnic vascular bed in the carotid sinus baroreceptor reflex control of vascular resistance and capacity was studied in nine pentobarbital-anesthetized dogs. The splanchnic circulation was vascularly isolated in an unopened abdomen and perfused at constant flow and venous pressure. Decreasing carotid sinus pressure from 200 to 50 mmHg resulted in a 72% increase in splanchnic vascular resistance and a decrease in splanchnic blood volume of 4.7 ml/kg. Changes in splanchnic inflow from 0 to 70 ml.min-1.kg-1 resulted in linear changes in splanchnic arterial pressure. Increasing carotid sinus pressure significantly decreased the slope (P less than 0.005) and intercept (P less than 0.025) of the splanchnic pressure-flow relationship. It is concluded that in the dog, the splanchnic vascular bed contributes a major portion of blood volume mobilized by the carotid sinus reflex.
Phosphoinositide metabolism and metabolism-contraction coupling in rabbit aorta
Authors: Coburn R. F. , Baron C. , Papadopoulos M. T.
Published: December 2017

We tested a hypothesis that metabolism-contraction coupling in vascular smooth muscle is controlled by the rate of delivery of energy to ATP-dependent reactions in the inositol phospholipid transduction system that generate second messengers exerting control on smooth muscle force. Rabbit aorta was contracted by norepinephrine (NOR) under conditions of normoxia and hypoxia (bath PO2 less than 40 mmHg), and changes in inositol phospholipid pool sizes and metabolic flux rates (JF) were determined. JF was determined by labeling free cytosolic myo-inositol by incubation of unstimulated muscle with myo-[3H]inositol and then measuring rates of incorporation of this isotope into inositol phospholipids and inositol phosphates when the muscle was activated by NOR. JF measured during maintenance of NOR-induced force was markedly inhibited during hypoxia to 40-50% of that determined during normoxia; rates of increases in inositol phosphate radioactivities were similarly depressed during NOR activation under hypoxia. The hypoxia-induced decrease in JF was associated with four- to fivefold increase in phosphatidylinositol 4-phosphate (PIP) total pool size, suggesting PIP kinase was inhibited and rate limiting. Total pool sizes of phosphatidylinositol, phosphatidylinositol bisphosphate, and phosphatidic acid were unchanged from values seen during activation under normoxia. These data suggest that activation of inositol phospholipid metabolism, which generates inositol 1,4,5-trisphosphate (IP3) and diacylglycerol, is blunted under conditions where aerobic energy production is inhibited. Data are consistent with “rate-limiting” effects of decreased ATP delivery, or decreased phosphate potential, on PIP kinase and reactions that control resynthesis of phosphatidylinositol.