Arteriolar responses to norepinephrine and ouabain in early 1-kidney, 1-clip hypertension in rats

1985 ◽  
Vol 249 (4) ◽  
pp. H851-H858
Author(s):  
H. W. Overbeck
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Response Curves ◽  
Sodium Potassium ◽  
Inotropic Effects ◽  
Arteriolar Wall ◽  
Vascular Beds ◽  
Normotensive Control

We assessed the role of putative circulating ouabainlike factors on in vivo arteriolar function in rats with very early (less than or equal to 7 days, mean 3 days), benign, one-kidney, one-clip (1K1C) hypertension. Thus we measured vascular responses in vasodilated (nitroprusside or adenosine), vascularly isolated, innervated hindlimb vascular beds of chloralose-anesthetized 1K1C rats perfused with their own blood at 1 ml/min. Complete dose-response curves to norepinephrine in 19 1K1C compared with 25 uninephrectomized (1K) normotensive control rats showed unchanged thresholds and 50% effective dosages. Magnitude of ouabain-induced leftward shifts of the dose-response curve in 29 1K1C and 30 1K rats were similar. In 1K1C, compared with 1K, limb resting resistance was elevated by 45% (P less than 0.001), and limb resistance at maximal vasodilation was elevated by 15% (P less than 0.02). These results provide no evidence in this form and stage of hypertension that humoral ouabainlike inhibitors of the sodium-potassium pump evoke physiologically significant inotropic effects in arterioles in vivo. However, the results suggest that significant increases in arteriolar wall-to-lumen ratio occur in the earliest stages (3 days) of hypertension and probably contribute to the elevated resistance.

Role of Endothelial K + Channels in NO-Dependent Vasorelaxant Responses to Acetylcholine in Rat Aorta.

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 698-698
Author(s):  
John Quilley ◽  
Yue Qiu
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Rat Aorta ◽  
Dose Response Curve ◽  
Response Curves ◽  
K Channels ◽  
Voltage Dependent ◽  
The Right ◽  
Stimulation Of

P30 Endothelium-dependent vasorelaxant responses to acetylcholine (Ach) in rat aorta are mediated solely by NO. Rings precontracted with U46619 were used to investigate the role of endothelial K + channels. Thus, any effect of K + channel inhibitors on Ach responses in the absence of an effect on those to nitroprusside (NP) can be attributed to interference with Ach-induced stimulation of NO. Vasorelaxant responses to Ach (log EC 50 -7.29M) were abolished by removal of the endothelium or inhibition of NO synthesis with nitroarginine (100μM) which potentiated responses to NP (log EC 50 -9.41M vs -8.47M for control). In the presence of TEA (10mM) to inhibit K + channels, the dose-response curve for Ach, but not NP, was shifted to the right (log EC 50 -6.06). Elevation of extracellular K + (25mM KCl)also shifted the dose-response curve for Ach to the right. Inhibitors of specific types of K + channels: BaCl 2 (30μM), apamin (100nM), glibenclamide (10μM), charybdotoxin (50nM) and iberiotoxin (100nM) were without effect on dose-response curves to either Ach or NP. However, the combination of apamin (100nM) and charybdotoxin (50nM) but not apamin plus iberiotoxin, reduced relaxant responses to Ach (log EC 50 -6.95M) without affecting those to NP.These results confirm that Ach-induced relaxation of rat aorta is mediated entirely by endothelium-derived NO, the release of which apparently involves hyperpolarization of the endothelium. This effect is dependent on activation of a K + channel that is blocked by a combination of apamin/charybdotoxin but neither agent alone, possibly indicating characteristics of both Ca 2+ - activated and voltage-dependent K + channels.

Role of potassium channels in hypoxic relaxation of porcine bronchi in vitro

1994 ◽  
Vol 266 (3) ◽  
pp. L232-L237
Author(s):  
K. S. Lindeman ◽  
L. B. Fernandes ◽  
T. L. Croxton ◽  
C. A. Hirshman
Keyword(s):  
Smooth Muscle ◽  
Dose Response ◽  
Katp Channel ◽  
Response Curve ◽  
Channel Blocker ◽  
Katp Channels ◽  
Response Curves ◽  
Third Order

To elucidate the mechanism of hypoxic relaxation of airway smooth muscle in vitro, we investigated the role of adenosine triphosphate-sensitive potassium (KATP) channels in this response. Second- and third-order porcine bronchial rings were suspended in 10-ml organ baths containing Krebs-Henseleit solution. To demonstrate the presence of KATP channels in this tissue, bronchial rings were contracted with carbachol (1 microM) in the presence of glibenclamide (100 microM), a KATP channel blocker, or the vehicle dimethyl sulfoxide (DMSO) (0.1 ml), and dose-response curves to levcromakalim (a KATP channel opener) or isoproterenol were constructed. In separate experiments, either glibenclamide or DMSO was added to the chamber and rings were contracted with carbachol (1 microM) in the presence of 95% O2-5% CO2. At the plateau, airways were relaxed with either isoproterenol (0.1 or 0.3 microM) or hypoxia (50, 28, or 0% O2, with constant 5% CO2). Glibenclamide, when compared with DMSO, shifted the dose-response curve to levcromakalim, but not to isoproterenol. Glibenclamide attenuated hypoxic relaxation in rings exposed to 50% O2 (from 35 +/- 4% to 23 +/- 3%, n = 6, P < 0.001) and increased the time to 63% relaxation in rings exposed to 50% O2 or to 28% O2. Responses in rings exposed to 0% O2 or to isoproterenol (0.1 or 0.3 microM) were not significantly altered. The ability of glibenclamide to attenuate the maximum response to 50% O2 and to increase the time to 63% relaxation during exposure to 50 or 28% O2 suggests that one component of hypoxic bronchodilation during moderate degrees of hypoxia is opening of KATP channels.

scholarly journals Correspondence of In Vitro and In Vivo Fluconazole Dose-Response Curves for Cryptococcus neoformans

2005 ◽  
Vol 49 (8) ◽  
pp. 3297-3301 ◽  
Author(s):  
Robert A. Larsen ◽  
Madeline Bauer ◽  
Ann M. Thomas ◽  
Alejandro Sanchez ◽  
Diane Citron ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Dose Response ◽  
Response Curve ◽  
Drug Susceptibility Testing ◽  
Response Curves ◽  
In Vitro Susceptibility ◽  
Drug Concentrations ◽  
Wide Range

ABSTRACT We conducted in vitro experiments to evaluate the susceptibility of a clinical isolate of Cryptococcus neoformans to a wide range of concentrations of fluconazole. In vitro susceptibility was tested using broth macrodilution methods modified to provide a numeric count of viable organisms. The association between the quantitative in vitro response and fluconazole drug concentrations was estimated using local nonparametric regression. Regression analysis was used to assess the correspondence between the in vitro fluconazole concentration-response curve and the murine dose-response curve observed in our previously reported murine model. The regression model was then used to predict the murine response. There was a strong correspondence between in vitro measures of response to fluconazole alone and the previously reported biologic effects seen in the mouse. In vitro antifungal drug susceptibility testing can reliably predict the murine response to fluconazole.

Bioassay by cross-perfusion for circulating inotropic factor in hypertension

1988 ◽  
Vol 254 (2) ◽  
pp. H230-H237
Author(s):  
H. W. Overbeck
Keyword(s):  
Normal Male ◽  
Response Curves ◽  
Humoral Factors ◽  
Inotropic Effects ◽  
Arteriolar Resistance ◽  
Effective Doses ◽  
Vascular Beds ◽  
Alpha Chloralose ◽  
Minimal Resistance

To study inotropic effects of blood from one-kidney, one-clip (1K,1C) rats with early (less than 7 days) or chronic (greater than 4 wk) benign hypertension, we assessed arteriolar resistance and norepinephrine (NE) responses in vascularly isolated, innervated assay hindlimb vascular beds of alpha-chloralose-anesthetized, normal male recipient rats. Hindlimbs were cross-perfused (2 ml/min) with blood from anesthetized donor rats with limb outflow returned to the donor rat. Perfusion pressure was monitored. Complete NE (injected intra-arterially) dose-response curves in limbs perfused with donor blood from nine early 1K,1C rats, compared with nine appropriate normotensive control donor rats, indicated unchanged thresholds, 50% effective doses, and maximal responses. Curves in limbs perfused with blood from 10 chronic 1K,1C, compared with 10 appropriate controls, suggested small (P less than 0.02) leftward shifts. Decreases (P less than 0.01) in maximal responses were also observed. Limb resting resistance and minimal resistance (sodium nitroprusside) did not rise, even after 4-5 h of cross-perfusion. These results provide no evidence in early 1K,1C and little evidence in chronic 1K,1C that humoral factors, including ouabainlike inhibitors, evoke physiologically significant inotropic effects in arterioles in vivo.

Synergism between Tissue-Type Plasminogen Activator and a Genetically Engineered Variant Lacking the Finger Domain, the Growth Factor Domain and the First Kringle Domain

1991 ◽  
Vol 65 (03) ◽  
pp. 286-290 ◽  
Author(s):  
C Mattson ◽  
K Wikström ◽  
C Sterky ◽  
G Pohl
Keyword(s):  
Synergistic Effect ◽  
Dose Response ◽  
Response Curve ◽  
Tissue Type ◽  
Lag Phase ◽  
Individual Dose ◽  
Response Curves ◽  
Type Plasminogen Activator

SummaryA modified variant of human tissue-type plasminogen activator (t-PA) lacking the finger domain (F), the growth factor domain (G) and the first kringle domain (K1), has an extended plasma half-life in vivo, compared to that of t-PA. When the variant (denoted K2P) was tested in vitro for its ability to lyse human plasma clots we found that the activity was characterized by a time lag phase and a sigmoidal dose-response curve. However, an attenuation of the lag phase in vitro was observed both when K2P was mixed with t-PA in a w/w ratio of 4 : 1 and when K2P was allowed to lyse a clot that had been pre-exposed to t-PA i.e. submitted to a limited plasmic digestion. Dosis that in vitro caused 50% lysis within 6 h were calculated from individual dose-response curves and were for K2P, t-PA and K2P/t-PA (4 : 1 w/w) 540 ng/ml, 360 ng/ml and 310 ng/ml, respectively. These results indicated a synergistic effect between K2P and t-PA. However, the data from individual dose-response curves showed that the effect of the K2P/t-PA mixture never was better than that of t-PA alone, and the synergistic effect in vitro is therefore considered to be of limited use. The thrombolytic activity in vivo was evaluated in a rabbit jugular vein thrombus model. Despite the lag phase observed in vitro, K2P was approximately 3 times as effective as t-PA in vivo (bolus injection). The thrombolytic effect of K2P was further potentiated when it was administred together with a small amount of t-PA (4 : 1 w/w). This potentiation in vivo was, in contrast to the effect in vitro, a useful synergistic effect as the dose-response curve for the K2P/t-PA mixture was steeper than that of t-PA and K2P alone. Doses that caused 50% lysis within 3 h were for t-PA, K2P and K2P/t-PA 1.28 mg/kg, 0.56 mg/kg and 0.35 mg/kg, respectively.

Effects of inhaled substance P on airway responsiveness to methacholine in asthmatic subjects in vivo

1994 ◽  
Vol 77 (3) ◽  
pp. 1325-1332 ◽  
Author(s):  
D. Cheung ◽  
H. van der Veen ◽  
J. den Hartigh ◽  
J. H. Dijkman ◽  
P. J. Sterk
Keyword(s):  
Substance P ◽  
Dose Response ◽  
Forced Expiratory Volume ◽  
Maximal Response ◽  
Response Curves ◽  
Airway Narrowing ◽  
Dose Response Curves ◽  
High Doses

We tested the hypothesis that the inhaled tachykinin substance P (SP) can induce hyperresponsiveness to methacholine in asthmatic subjects in vivo. Nine atopic nonsmoking asthmatic males with normal forced expiratory volume in 1 s (FEV1; > 80% predicted) and increased methacholine sensitivity [provocative concn causing 20% fall in FEV1 (PC20) < 8 mg/ml] participated in a two-period placebo-controlled crossover study. Dose-response curves to SP (0.25–8 mg/ml) and placebo were recorded on 2 randomized days at least 1 wk apart, and methacholine tests were done 24 h before and 2 and 24 h after these challenges. The responses were measured by FEV1 (%fall from baseline). The position of the methacholine dose-response curves was expressed by the PC20 FEV1 and by the maximal response by the plateau level (MFEV1). SP caused a dose-dependent fall in FEV1 (P < 0.001). There was a slight increase in the PC20 FEV1 at 2 and 24 h, which was not significantly different between placebo and SP. Similarly, there was a reduction in MFEV1 at 2 h after both pretreatments. However, at 24 h after SP inhalation, MFEV1 increased compared with placebo. These changes in MFEV1 were significantly different between SP and placebo by 5.2 +/- 2.2% fall (SE) (P < 0.05). We conclude that 1) a bronchoconstrictive dose of SP, compared with placebo, enhances maximal airway narrowing to methacholine in asthma 24 h after inhalation and 2) tolerance develops to high doses of inhaled methacholine. These findings are suggestive of a role of SP in causing excessive airway narrowing in asthma by inflammatory mechanisms.

Effects of epinephrine on insulin-mediated glucose uptake in whole body and leg muscle in humans: role of blood flow

1992 ◽  
Vol 263 (2) ◽  
pp. E199-E204 ◽  
Author(s):  
M. Laakso ◽  
S. V. Edelman ◽  
G. Brechtel ◽  
A. D. Baron
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Glucose Uptake ◽  
Dose Response ◽  
Insulin Dose ◽  
Whole Body ◽  
Response Curves ◽  
Leg Muscle

In vivo insulin-mediated glucose uptake (IMGU) occurs chiefly in skeletal muscle, where it is determined by the product of arteriovenous glucose difference (delta AVG) and blood flow (BF) rate into muscle. Epinephrine (Epi) reduces the rate of IMGU in whole body. To examine whether this is due to a reduction in delta AVG across or BF into skeletal muscle we constructed insulin dose-response curves for whole body IMGU and leg muscle IMGU- using euglycemic clamp ((+)[3-3H]glucose infusion) and leg balance techniques during insulin infusions ranging from 10 to 1,200 mU.m-2.min-1. We studied six subjects [wt 70 +/- 2 (SE) kg] during an Epi infusion at a single rate of 0.002 mg.kg-1.min-1 and six subjects (70 +/- 3 kg) during a saline infusion alone. Maximum whole body glucose uptake (WBGU) was similar during Epi and saline infusions [71.4 vs. 73.6 mmol.kg-1.min-1, P = not significant (NS)]. Compared with saline, maximum delta AVG was decreased during Epi infusion (1.04 vs. 1.31 mM, P less than 0.01). Compared with saline alone maximum leg BF was increased (5.3 vs. 4.3 dl/min, P less than 0.01) during Epi infusion. Thus maximum leg glucose uptake (LGU) was similar (696 vs. 821 pmol.leg-1.min-1, P = NS) during infusion of Epi and saline, respectively. Half-maximal effective dose for insulin's effect to stimulate WBGU, delta AVG, BF, and LGU was increased two- to threefold during Epi vs. saline infusions (P less than 0.01 for all values).(ABSTRACT TRUNCATED AT 250 WORDS)

Factor VII Clotting Assay: Influence of Different Thromboplastins and Factor VII-Deficient Plasmas

1991 ◽  
Vol 65 (02) ◽  
pp. 160-164 ◽  
Author(s):  
Marina Poggio ◽  
Armando Tripodi ◽  
Guglielmo Mariani ◽  
Pier Mannuccio Mannucci ◽  
Keyword(s):  
Heart Disease ◽  
Ischemic Heart Disease ◽  
Dose Response ◽  
Response Curve ◽  
Ischemic Heart ◽  
Factor Vii ◽  
Response Curves ◽  
Assay Sensitivity ◽  
Clinical Laboratories ◽  
Coagulant Activity

SummaryBeing a putative predictor of ischemic heart disease, the measurement of factor VII (FVTI) coagulant activity will be presumably requested to clinical laboratories with increasing frequency. To assess the influence on FVII assays of different thromboplastins and FVII-deficient plasmas we compared performances of all possible combinations of 5 thromboplastins and 6 deficient plasmas. The reproducibility of the clotting times of the dose-response curves for human and rabbit thromboplastins were acceptable (CV lower than 7%), whereas bovine thromboplastin had a higher CV. Reproducibility was very similar for all deficient plasmas when they were used in combination with a given thromboplastin. Responsiveness of the dose-response curve did not depend on the deficient plasma but rather on the thromboplastin: one rabbit thromboplastin was the least responsive, the bovine thromboplastin the most responsive, the human and the remaining two rabbit thromboplastins had intermediate responsiveness. Assay sensitivity to cold-activated FVII varied according to the thromboplastin: the bovine thromboplastin was the most sensitive, the human thromboplastin the least sensitive, of the three rabbit thromboplastins two were relatively sensitive, one was almost insensitive. In conclusion, our results indicate that thromboplastin rather than deficient plasma is the crucial factor in the standardization of FVII assay.

OVARIAN ASCORBIC ACID DEPLETION TEST FOR LUTEINIZING HORMONE

1967 ◽  
Vol 56 (4) ◽  
pp. 619-625 ◽  
Author(s):  
Hans Jacob Koed ◽  
Christian Hamburger
Keyword(s):  
Ascorbic Acid ◽  
Luteinizing Hormone ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Human Origin ◽  
Response Curves ◽  
Significant Difference ◽  
The Mean ◽  
Different Levels

ABSTRACT Comparison of the dose-response curves for LH of ovine origin (NIH-LH-S8) and of human origin (IRP-HMG-2) using the OAAD test showed a small, though statistically significant difference, the dose-response curve for LH of human origin being a little flatter. Two standard curves for ovine LH obtained with 14 months' interval, were parallel but at different levels of ovarian ascorbic acid. When the mean ascorbic acid depletions were calculated as percentages of the control levels, the two curves for NIH-LH-S8 were identical. The use of standards of human origin in the OAAD test for LH activity of human preparations is recommended.

scholarly journals Predicting the in vivo developmental toxicity of benzo[a]pyrene (BaP) in rats by an in vitro–in silico approach

2021 ◽  
Author(s):  
Danlei Wang ◽  
Maartje H. Rietdijk ◽  
Lenny Kamelia ◽  
Peter J. Boogaard ◽  
Ivonne M. C. M. Rietjens
Keyword(s):  
Dose Response ◽  
In Silico ◽  
Response Curve ◽  
Developmental Toxicity ◽  
Toxicity Testing ◽  
Maximal Effect ◽  
Blood Concentrations ◽  
Reverse Dosimetry

AbstractDevelopmental toxicity testing is an animal-intensive endpoints in toxicity testing and calls for animal-free alternatives. Previous studies showed the applicability of an in vitro–in silico approach for predicting developmental toxicity of a range of compounds, based on data from the mouse embryonic stem cell test (EST) combined with physiologically based kinetic (PBK) modelling facilitated reverse dosimetry. In the current study, the use of this approach for predicting developmental toxicity of polycyclic aromatic hydrocarbons (PAHs) was evaluated, using benzo[a]pyrene (BaP) as a model compound. A rat PBK model of BaP was developed to simulate the kinetics of its main metabolite 3-hydroxybenzo[a]pyrene (3-OHBaP), shown previously to be responsible for the developmental toxicity of BaP. Comparison to in vivo kinetic data showed that the model adequately predicted BaP and 3-OHBaP blood concentrations in the rat. Using this PBK model and reverse dosimetry, a concentration–response curve for 3-OHBaP obtained in the EST was translated into an in vivo dose–response curve for developmental toxicity of BaP in rats upon single or repeated dose exposure. The predicted half maximal effect doses (ED50) amounted to 67 and 45 mg/kg bw being comparable to the ED50 derived from the in vivo dose–response data reported for BaP in the literature, of 29 mg/kg bw. The present study provides a proof of principle of applying this in vitro–in silico approach for evaluating developmental toxicity of BaP and may provide a promising strategy for predicting the developmental toxicity of related PAHs, without the need for extensive animal testing.

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