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At least 1,333 records · Page 74Linked to original sources
PubMed1997

Sleeve recording of upper esophageal sphincter resting pressures during cricopharyngeal myotomy.

OBJECTIVE: The manometric effects of a 6-cm cricopharyngeal myotomy are recorded while the operation is being performed from cervical esophagus to the cricopharyngeus and then to the hypopharynx. SUMMARY BACKGROUND DATA: Cricopharyngeal myotomy is used in the treatment of oropharyngeal dysphagia of different causes. The operation decreases the resting pressure in the upper esophageal sphincter (UES). The components responsible for this decrease have not been clarified. METHODS: Fourteen patients with oropharyngeal dysphagia underwent a sleeve recording of the UES resting pressures under general anesthesia before and after sequential myotomy of the pharyngoesophageal junction. Patients were assessed in the awake state before and after the whole myotomy. RESULTS: Upper esophageal pressures remain unchanged after division of 2 cm of the cervical esophageal muscle. Section of 2 cm of the cricopharyngeal area results in a significant decrease of the sphincter resting pressure (p < 0.01). The division of 2 cm of hypopharyngeal muscle results in a further significant reduction of the resting pressure (p < 0.005). CONCLUSIONS: Extension of the cricopharyngeal myotomy over hypopharyngeal musculature produces a more significant decrease of UES resting pressure.

Aged↗
PubMed2004

Coaxing HIV-1 from resting CD4 T cells: histone deacetylase inhibition allows latent viral expression.

BACKGROUND: Histone deacetylase (HDAC), a host mediator of gene repression, inhibits HIV gene expression and virus production and may contribute to quiescence of HIV within resting CD4 T cells. OBJECTIVES: To test the ability of valproic acid (VPA), an inhibitor of HDAC in clinical use, to induce expression of HIV from resting CD4 T cells. METHODS: Chromatin immunoprecipitation measured the capability of VPA to deacetylate the HIV promoter, a remodeling of chromatin linked to gene expression. The effect of VPA on resting CD4 T cell phenotype was measured by flow cytometric analysis, and its effect on de novo HIV infection of peripheral blood mononuclear cells was measured ex vivo. Outgrowth of HIV from resting CD4 T cells of aviremic, HIV-infected donors treated with highly active antiretroviral therapy was compared in limiting-dilution cultures after mitogen stimulation or exposure to VPA. RESULTS: VPA induced acetylation at the integrated HIV proviral promoter, but CD4 cells exposed to VPA did not become activated or more permissive for de novo HIV infection. VPA induced outgrowth of HIV from the resting CD4 cells of aviremic patients at concentrations achievable in vivo as frequently as did mitogen stimulation. CONCLUSIONS: With advances in antiretroviral therapy, HIV infection might be cleared by intensive time-limited treatment coupled with practical strategies that disrupt latency without enhancing new infection. HDAC inhibitors are capable of inducing expression of quiescent provirus, without fully activating cells or enhancing de novo infection, and may be useful in future clinical protocols that seek to eradicate HIV infection.

Acetylation↗
PubMed1990

Long-term haemodynamic effects of amlodipine at rest and during exercise in essential hypertension.

The long-term haemodynamic responses to amlodipine, a new long-acting calcium antagonist, were studied both at rest and during exercise in 18 patients (mean age 43 years) with essential hypertension. Blood pressure was measured intra-arterially, cardiac output by dye dilution and heart rate by electrocardiogram. After 11 months of treatment with 5-10 mg amlodipine once daily (mean dose 9 mg/day), mean arterial pressure was reduced by 14% sitting at rest. The reduction in blood pressure was associated with a marked reduction in the total peripheral resistance index (TPRI) of 19% (P less than 0.001). Similar responses were seen supine at rest and during 50W, 100W and 150W bicycle exercise. No significant changes were seen in heart rate. There was a slight increase in stroke index, and cardiac index was preserved at rest and during exercise with a slight trend towards an increase. In 10 of the patients, blood pressure was monitored by a portable blood pressure recorder (Accutracker II, Suntech Medical instruments, Raleigh, North Carolina, USA). Blood pressure was well controlled throughout the full 24 h period after one daily dose. In conclusion, amlodipine exerts a clear antihypertensive effect, both at rest and during exercise, through reduction in the TPRI and without a fall in cardiac pump function. No changes in heart rate were seen and there was no tendency for a reduction in the stroke index during 8 min of exercise at 150 W; on the contrary there was a trend towards an increase. The incidence of side-effects was low (ankle oedema in two patients).

Amlodipine↗
PubMed1998

Haemodynamic effects of inhibition of nitric oxide synthase and of L-arginine at rest and during exercise.

OBJECTIVE: To compare effects of N(G)-monomethyl-L-arginine (L-NMMA; a NO synthase inhibitor) and L-arginine (a NO synthase substrate) on haemodynamics in healthy men at rest and during exercise. METHODS: We infused L-NMMA and saline placebo intravenously in two groups of eight healthy men. Each group underwent a two-phase, randomized, single-blind crossover study. Men in one group received 3 mg/kg L-NMMA and men in the other group received 6 mg/kg L-NMMA. Haemodynamic measurements were performed before, during and after a 12 min stepped exercise protocol starting 6 min after the intravenous infusion. A further six men received, according to the same study design, 30 g L-arginine over 30 min and saline placebo before exercise. Blood pressure was measured by sphygmomanometry and cardiac output by bioimpedance, allowing computation of total systemic vascular resistance index (SVRI). RESULTS: Infusion of 6 mg/kg L-NMMA into men at rest produced modest increases (compared with effect of saline placebo) in systolic and diastolic blood pressures of 4.1 +/- 1.1 and 12.6 +/- 3.5%, respectively (means +/- SEM, P < 0.01 for both comparisons) and a marked increase in SVRI of 39.2 +/- 5.2% (P < 0.01). Cardiac index and heart rate were 22.0 +/- 3.3 and 17.0 +/- 4.4% lower after administration of L-NMMA (P < 0.01 for each comparison) than after infusion of saline placebo. During exercise there was no significant difference between total SVRI after infusions of L-NMMA and saline (difference not significant, diminished with increasing exercise). Six minutes into recovery the difference between total SVRI after infusions of L-NMMA and saline reappeared with SVRI 25 +/- 6.9% higher after infusion of L-NMMA than after infusion of saline (P < 0.01). Administration of L-arginine had no significant effect on haemodynamics in men at rest, during exercise and during recovery. CONCLUSIONS: Effects of L-NMMA on total systemic vascular resistance during exercise are less marked than are those on subjects at rest, probably because vasodilatation of resistance vessels of skeletal muscle during exercise is mediated mainly by factors other than NO. Our results also suggest that NO synthesis in healthy men is not substrate limited either at rest or during exercise.

Adult↗
PubMed1990

Chronic hemodynamic effects of tiapamil and felodipine in essential hypertension at rest and during exercise.

Sixteen men with previously untreated diastolic blood pressure of 100-120 mm Hg were studied hemodynamically at rest supine and sitting and during a 100 W bicycle exercise. Blood pressure (BP) was recorded intra-arterially, and cardiac output (CO) by the dye-dilution method. After initial study, patients were treated with tiapamil in increasing doses (300-600 mg b.i.d., with a mean daily dose of 980 mg). The patients were restudied and then changed to felodipine (5-10 mg b.i.d., with a mean daily dose of 15 mg). Casual (cuff) BP at rest sitting was as follows: end placebo, 166/105 mm Hg; 1 year of tiapamil, 148/92 mm Hg; 1 year of felodipine, 139/86 mm Hg. Pretreatment hemodynamic results at rest sitting were as follows: BP, 169/105 mm Hg; MAP, 129 mm Hg; cardiac index (CI), 2.43 L/min/m2; total peripheral resistance index (TPRI), 4,305 dyn s/cm-5/m2. Both drugs reduced systolic (SAP), diastolic (DAP), and mean (MAP) arterial pressure significantly in all situations. BP reduction seemed to be more pronounced on felodipine than on tiapamil. Felodipine reduced MAP by 15% at rest supine, 14% at rest sitting, and 11% during exercise. The BP reduction was entirely due to reduction in TPRI (15, 16, and 13%, respectively). CI as well as stroke index (SI) and heart rate (HR) were unchanged. Tiapamil did not reduce TPRI significantly and the fall in BP was due to a combination fall in TPRI and CI.

Adult↗
PubMed2003

Comparison of 99mTc-sestamibi-18F-fluorodeoxyglucose dual isotope simultaneous acquisition and rest-stress 99mTc-sestamibi single photon emission computed tomography for the assessment of myocardial viability.

Dual isotope simultaneous acquisition single photon emission computed tomography (DISA SPECT) offers the advantage of obtaining information on myocardial perfusion using Tc-sestamibi ( Tc-MIBI) and metabolism using F-fluorodeoxyglucose ( F-FDG) in a single study. The prerequisite is that the Tc-MIBI images are not degraded by scattered 511 keV photons or poor count statistics due to the lower efficiency of the extra high energy (EHE) collimator. Therefore, we compared the registered Tc-MIBI uptake and image quality of DISA and single isotope acquisition. Furthermore, we investigated whether DISA yields additional information for the assessment of myocardial viability in comparison with rest-stress Tc-MIBI. Nineteen patients with known coronary artery disease and irreversible perfusion defects on previous rest-stress MIBI test studies were investigated. After oral glucose loading and simultaneous injection of 600 MBq of Tc-MIBI and 185 MBq of F-FDG at rest, DISA was performed using energy windows of 140 (+/-15%), 170 (+/-20%) and 511 keV (+/-15%). Planar 140 keV images were corrected for scatter by subtraction using the 170 keV window. The single and dual isotope Tc-MIBI images were both displayed in a polar map with 128 segments normalized to maximum counts. F-FDG and Tc-MIBI images were visually scored for a perfusion-metabolism mismatch pattern using nine regions per heart. There was an excellent correlation (r =0.93, P<0.0001) between the Tc-MIBI uptake detected in the single and dual isotope acquisition. The average difference between the dual and single isotope Tc-MIBI uptake was -1.2% (not significantly different from zero) and the coefficient of variation of the difference was 8.7%. Of the 79 regions with irreversible perfusion defects on previous rest-stress Tc-MIBI, six regions in five patients showed a perfusion-metabolism mismatch pattern. We conclude that DISA does not affect the quality of the Tc-MIBI images. Furthermore, F-FDG- Tc-MIBI DISA may show viability in a small but significant (7.6%, P<0.0034) number of regions with irreversible perfusion defects on rest-stress Tc-MIBI.

Adult↗
PubMed1985

Does performance of tasks affect the resting focus of accommodation?

Measurements of the resting focus of accommodation were obtained with an infrared optometer while subjects engaged in four tasks: (1) passive viewing in darkness; (2) passive viewing of a laser speckle pattern; (3) active judgment of motion in a laser speckle pattern; and (4) mental arithmetic in darkness. The results showed resting focus measures to be comparable under all four conditions for some subjects. However, other subjects exhibited consistent increases or decreases in the resting focus position when asked to judge the direction of speckles within the laser test pattern or perform mental arithmetic. This finding suggests that "effort to see" may influence the resting focus of some subjects. Implications for measurement procedures and population estimates of the resting focus are discussed.

Accommodation, Ocular↗
PubMed1996

Differential sensitivity of resting and IL-2 activated NK cells to R-verapamil.

Natural killer (NK) cells are the first lymphoid population to reconstitute the peripheral blood compartment of immunologically compromised bone marrow transplant (BMT) recipients. Recent data suggest that, among patients transplanted for leukemia, NK cells can prevent or delay disease relapse by mediating a cytotoxic graft vs leukemia (GvL) response. Although the major mechanism by which NK cells mediate target cell lysis involves degranulation and release of cytolytic effector molecules (granzymes, proteoglycans, perforin), accumulating evidence suggests that NK cells possess additional pathways to mediate target cell killing. In fact, it is well recognized that recombinant cytokines such as IL-2 enhance the in vitro cytolytic activity of NK cells. In this study, we observed that the lytic activity mediated by resting and IL-2 activated NK cells against the same target cell appears to occur via two distinct pathways, as distinguished by their differential response to R-verapamil. Specifically, we observed that 25 microM R-verapamil inhibited the lytic activity of resting NK cells against K562 targets by approximately 50%. However, the lytic activity of IL-2 activated NK cells was unaffected by this concentration of R-verapamil. Additional studies suggested that the inhibitory effect of R-verapamil on NK cytotoxic activity was associated with its ability to prevent degranulation of cytotoxic granules. Specifically, R-verapamil inhibited BLT esterase release from resting but not IL-2 activated NK cells. These data suggest that IL-2 activated NK cells can promote target cell lysis by a pathway (possibly degranulation independent) distinct from that used by resting NK cells. We speculate that the target of R-verapamil on resting NK cells is P-glycoprotein (Pgp), an ABC transporter that we recently reported was expressed on NK cells and whose functional activity is known to be inhibited by R-verapamil.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1987

Interleukin-2 stimulates resting human T lymphocytes' response to allogeneic, gamma interferon-treated keratinocytes.

In order to investigate the biologic significance of HLA-DR expression by human keratinocytes, we have examined the possibility that DR-positive keratinocytes become alloantigen presenting cells for resting T cells in the presence of interleukin-2. Using this system, gamma interferon-treated, DR-positive keratinocytes stimulate the proliferation of allogeneic, resting T cells approximately 3-fold whereas non-gamma interferon-treated, DR-negative keratinocytes do not. Because a monoclonal antibody against recombinant gamma interferon inhibits this proliferation, the stimulation is dependent on pre-incubation with gamma interferon. By contrast, since the stimulation is not inhibited by a monoclonal antibody against HLA-DR, it is not clear that the stimulation is due to class II antigen expression by keratinocytes. To rule out that gamma interferon increases the expression of class I antigens, leading to stimulation of resting T cells on that basis, we determined whether gamma interferon treatment enhances class I antigen expression by keratinocytes. The lymphokine treated cells did not demonstrate more class I antigen expression than untreated keratinocytes. Thus, the observed stimulation of allogeneic, resting T cells by gamma interferon-treated keratinocytes in the presence of IL-2 is not due to increased class I antigen expression but is due to other cell surface antigen(s) induced by recombinant gamma interferon treatment. These results suggest that gamma interferon-exposed keratinocytes in the presence of interleukin-2 may augment the activation of resting T lymphocytes and, in this manner, may contribute to cutaneous inflammation.

Antibodies, Monoclonal↗
PubMed1976

Hemodynamic long-term effects of timolol at rest and during exercise in essential hypertension.

Sixteen men with previously untreated essential hypertension in WHO stage I have been studied as out-patients. Oxygen consumption, heart rate (HR), cardiac output (Q) (Cardiogreen) and intraarterial brachial pressure were recorded at rest in supine and sitting position and during steady state work at 300, 600 and 900 kpm/min. The subjects were treated with timolol as the sole drug for one year and the hemodynamic study was repeated. BP was reduced approximately 18% at rest and 14% during exercise, HR approximately 26% and the cardiac index 28% at rest supine and 32% at rest sitting. During exercise the reductions in Q were 25-30%. The calculated total peripheral resistance was significantly increased at rest as well as during exercise. The product of mean arterial pressure and HR was reduced about 40%. No severe side-effects were seen.

Adrenergic beta-Antagonists↗
PubMed1983

Effect of disruption by sonication under different conditions on the activity of glucose dehydrogenase from resting spores of Bacillus subtilis.

The activity of glucose dehydrogenase present in resting spores of Bacillus subtilis varied strikingly with the conditions for disrupting the spores by sonic treatment, namely, the time and strength of sonication, and the type and pH of the solution used for suspending the spores. When the resting spores were sonicated for 30 min at a current of 1.45 A in 100 mM phosphate buffer in the range of pH 6.0 to 6.6 or in deionized water, the enzyme activity of the former suspension was approximately 10 times higher than that of the latter suspension. However, the enzyme activity of the latter was markedly stimulated in the presence of sodium chloride. The glucose dehydrogenase from resting spores disrupted in 100 mM phosphate buffer (pH 6.6) was a salt-independent, active enzyme with a molecular weight of about 120,000, whereas the enzyme from resting spores disrupted in deionized water was a salt-dependent, inactive one with a molecular weight of about 55,000. A high concentration of dipicolinic acid strongly inhibited activation by a salt of inactive glucose dehydrogenase from resting spores in deionized water, suggesting one of its several important roles in vivo.

Bacillus subtilis↗
PubMed1977

Comparison of the effects of labetalol and propranolol in healthy men at rest and during exercise.

1. Oral labeltalol and propranolol have been compared in healthy men with regard to the effects on heart rate, blood pressure and peak expiratory flow rate (PEFR) at rest and the changes induced by exercise. 2. Labetalol caused a dose-related reduction in standing diastolic pressure at rest whereas propranolol did not but neither drug altered standing systolic pressure at rest. 3. In the doses compared, propranolol was consistently more potent than labetalol in influencing blood pressure changes induced by exercise, in lowering heart rate at rest and reducing PEFR at rest. 4. Labetalol and propranolol are both beta-adrenoreceptor antagonists and the observed differences in the profiles of the two drugs are probably directly related to the additional alpha-adrenoreceptor blocking property of labetalol not possessed by propranolol. Because of these differences labetalol may be expected to have advantages in the treatment of hypertension.

Adult↗
PubMed1977

Effect of psychosocial stimuli and limbic lesions on prolactin at rest and following stress.

Many of the factors altering corticosterone in the rat have similar effects on prolactin. Resting prolactin, like corticosterone, is higher in animals housed singly than in those multiply housed. Unlike corticosterone, gentling did not lower prolactin. An exquisite sensitivity to environmental stimuli which results in rapid elevations in prolactin levels has been indentified in the rat which is considerably greater than that for corticosterone. Like corticosterone, the pattern of prolactin stress responses varies according to time of day. This differential sensitivity may well account for the diurnal variation in prolactin reported by some investigators. The limbic system has an important influence on prolactin. Lesions of the septal region do not modify resting levels but alter the pattern of prolactin stress responses in ways which are only partly similar to the effects of such lesions on corticosterone. In rhesus monkeys, individual variation in resting prolactin levels was observed, similar to that seen in the human. Levels are stable over periods of up to 50 days and are characteristic of the individual animal. In response to the stress of electric shock or shaping to a bar press response, prolactin elevation occurs only in animals with high resting levels, suggesting that a common mechanism is responsible for controlling both resting levels and magnitude of stress responses.

Animals↗
PubMed2005

Factors related to the resting tongue position among partially and completely edentulous subjects.

The prevalence of abnormal (retracted) position of the tongue at rest was examined in subjects with varying number of natural lower teeth. The aim of the study was to explore the relationship between tongue retraction and state of dentition and to identify potentially related parameters. The resting tongue positions were recorded in subjects partially edentulous in the lower jaw (n = 164) and compared with those met in dentate (n = 57) and completely edentulous participants (n = 84). Potentially related parameters, such as age, sex, duration of edentulism, palate vault and signs of temporomandibular disorders were also recorded. Tongue retraction was observed in a small percentage (12.3%) of the dentate, almost half (45.7%) of the partially edentulous and in the majority (67.8%) of the completely edentulous participants. The number of natural lower teeth correlated with the resting tongue position in the partially edentulous group. The tongue position at rest was also found weakly related to signs of temporomandibular disorders in the dentate group and to the sex and duration of edentulism in the partially edentulous group. It was concluded that the abnormal positioning of the resting tongue is increasingly observed with decreasing number of natural teeth, possibly in accordance with the morphological and functional alterations that result from teeth loss. The presence of a retracted tongue affects the complete denture construction; however, its effect on denture function remains questionable.

Adult↗
PubMed1995

Anopheles arabiensis and An. gambiae chromosomal inversion polymorphism, feeding and resting behaviour in relation to insecticide house-spraying in Tanzania.

Differential responses of the mosquitoes Anopheles arabiensis and An. gambiae sensu stricto to house-spraying with DDT or lambda-cyhalothrin were evaluated in relation to chromosomal inversion polymorphism, feeding and resting behaviour of these malaria vectors in Tanzania. Blood-fed mosquitoes from pit traps outdoors, exit traps on windows and indoor-resting catches were identified cytogenetically and the chromosomal inversion frequencies compared between samples and species. Their outdoor-resting behaviour was assessed by a mark-release-recapture experiment and by determining the proportion of freshly blood-fed individuals in exit traps. The source of bloodmeals was analysed by an ELISA method. Endophagic females of An. arabiensis were more likely than those of An.gambiae to exit from a house on the night of blood-feeding. Only in one out of three villages was there evidence that chromosomally distinct individuals within a species had different preferences for resting sites. There were indications, but not conclusive evidence, that mosquitoes caught indoors or outdoors had a tendency to return to the same type of resting site. In villages sprayed with either insecticide, the mean age of the vector populations was greatly reduced, compared with those in the unsprayed villages. An.arabiensis females exited from DDT sprayed houses after blood-feeding, whereas with lambda-cyhalothrin those exiting were mostly unfed and there was a decline in the human blood index. The excitorepellency of DDT was perceived as a disadvantage, whereas lambda-cyhalothrin apparently had more impact on malaria transmission by An.arabiensis.

Animals↗
PubMed1992

Comparative analysis of syngeneic and allogeneic mixed lymphocyte reaction of 'naturally' activated and resting T cells.

'Naturally' activated (NA) or resting T lymphocytes obtained from the spleen of normal BALB/c mice were compared in their capacity to mount a syngeneic mixed lymphocyte reaction (SMLR). Both T-cell subsets were able to proliferate and secrete IL-3/GM-CSF in SMLR cultures. IL-2 was present in 'resting' T-cell SMLR supernatants, and barely detectable in NA T-cell SMLR supernatants. Both NA and 'resting' T-cell SMLRs were inhibited with anti-class II, anti-CD4, or anti-IL-2R MoAbs. NA T cells exhibited a background proliferative and secretory activity in the absence of syngeneic accessory cells. This autonomous activity was susceptible to anti-CD4, but poorly inhibited with anti-class II MoAbs. Both NA and 'resting' T lymphocytes displayed strong responsiveness to allogeneic stimuli. The analysis of the relative frequency of proliferating cells in the SMLR (BALB/c), or allo-MLR (B10, B10.A, B10.D2) from NA or 'resting' T cells indicated an enrichment for syngeneic reactivity among NA T lymphocytes. The meaning of these results for NA T-cell function and repertoire is discussed.

Animals↗
PubMed2004

Comparison of the effects of fructose and glucose supplementation on metabolic responses in resting and exercising horses.

The aim of this study was to compare the effects of two different carbohydrate sources (fructose and glucose) on the metabolic responses in resting and exercising horses. The following regimes were fed in randomized order to five trained horses at rest and immediately before or during exercise. The resting regime comprised 0.6 kg grass meal pellets (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose. The exercise regime comprised 0.3 kg grass meal (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose fed immediately before or during simulated endurance exercise on a treadmill (30 km, total running time 120 min; 15 min rest after 60 min running time). Blood samples were collected for the analysis of glucose, insulin, free fatty acids (FFA) and lactate. In resting horses, glucose supplementation resulted in a significantly higher glycaemic and insulinaemic response than the control or fructose feedings (treatment P < 0.05). Plasma glucose levels were significantly higher after glucose supplementation given before or during exercise. Similar plasma glucose concentrations were observed after fructose was fed before exercise, whereas fructose supplementation during exercise resulted in a lower glycaemic response than glucose feeding (P < 0.05). Plasma insulin, FFA and lactate levels showed exercise-related changes (time P < 0.05), but treatment did not effect these results. Plasma glucose concentrations were elevated during the simulated endurance exercise after glucose feeding, and no counter-regulation by insulin occurred. The higher glycaemic response might be beneficial as exogenous glucose can be used as an energetic substrate during prolonged exercise. Fructose exhibited no clear advantages in comparison with glucose as a carbohydrate source for exercising horses.

Animal Feed↗
PubMed1995

Increased Ca2+ influx in the resting state maintains the myogenic tone and activates charybdotoxin-sensitive K+ channels in femoral arteries from young SHR.

1. To determine the possible role of voltage-dependent Ca2+ channels (VDCC) and Ca2+-activated K+ (KCa) channels in the regulation of resting tone of arteries from young spontaneously hypertensive rats (SHR), mechanical responses to the agents which interact with these channels were examined in endothelium-denuded strips of femoral arteries from 4 week old SHR and age-matched normotensive Wistar-Kyoto (WKY) rats. Systolic blood pressures at this age were not significantly different between SHR and WKY. 2. The strips from SHR, but not from WKY, maintained a myogenic tone; that is, the resting tone decreased when nifedipine was added. 3. Studies using 1 or 5 min pulse labelling of the strips with 45Ca showed that the basal Ca2+ influx was increased in SHR when compared with WKY, and this increase in SHR was abolished by nifedipine. Similar results were obtained when the cytoplasmic Ca2+ concentration ([Ca2+]i) in the resting state of the strips was measured by fura-PE3. 4. The addition of charybdotoxin (ChTX, a blocker of large conductance KCa channels) to the resting state caused a concentration-dependent contraction, which was much greater in SHR than in WKY. The ChTX-induced contraction in SHR was abolished by nifedipine. 5. In strips preloaded with 86Rb, the basal 86Rb efflux rate constant was significantly greater in SHR than in WKY. The increase in 86Rb efflux in SHR was abolished by nifedipine. 6. The results suggest that the Ca2+ influx via L-type VDCC was increased in the resting state of the femoral artery from 4 week old SHR, and therefore the myogenic tone was maintained and ChTX-sensitive K+ channels were highly activated.

Animals↗