Effects of in vivo cholinergic stimulation of rat exocrine pancreas

Peptide and cholinergic secretagogues both produce biphasic dose-response curves for pancreatic enzyme secretion in vitro: supraoptimal doses result in submaximal secretory responses. We compared the effects of maximal and supramaximal doses of a cholinergic agent (carbachol) on rat exocrine pancreas in vivo. In conscious rats, volume and enzyme output were measured from the cannulated pancreatic duct during infusion of carbachol for 3 h. Infusion of 5 X 10(-7) mol . kg-1 . h-1 carbachol caused optimal stimulation, whereas a supraoptimal dose (5 X 10(-6) mol . kg-1 . h-1) resulted in submaximal response. Similar results were achieved when discharge of amylase and protein synthesis was determined in vitro after carbachol in vivo. Supraoptimal doses of carbachol increased serum amylase and enhanced acinar cell lysosomal activity in the Golgi area. The latter appeared to induce fusion of zymogen granules, which resulted in cytoplasmic vacuoles. The in vivo results corroborate in vitro findings of a biphasic dose-response relationship for carbachol and demonstrate destructive effects of supraoptimal concentrations on target cells.

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Physiologically based kinetic modelling based prediction of in vivo rat and human acetylcholinesterase (AChE) inhibition upon exposure to diazinon

Archives of Toxicology ◽

10.1007/s00204-021-03015-1 ◽

2021 ◽

Author(s):

Shensheng Zhao ◽

Sebastiaan Wesseling ◽

Bert Spenkelink ◽

Ivonne M. C. M. Rietjens

Keyword(s):

Dose Response ◽

Kinetic Modelling ◽

Ache Inhibition ◽

Response Curves ◽

Alternative Testing ◽

Dose Response Curves ◽

Physiologically Based Kinetic Modelling ◽

Point Of Departure

AbstractThe present study predicts in vivo human and rat red blood cell (RBC) acetylcholinesterase (AChE) inhibition upon diazinon (DZN) exposure using physiological based kinetic (PBK) modelling-facilitated reverse dosimetry. Due to the fact that both DZN and its oxon metabolite diazoxon (DZO) can inhibit AChE, a toxic equivalency factor (TEF) was included in the PBK model to combine the effect of DZN and DZO when predicting in vivo AChE inhibition. The PBK models were defined based on kinetic constants derived from in vitro incubations with liver fractions or plasma of rat and human, and were used to translate in vitro concentration–response curves for AChE inhibition obtained in the current study to predicted in vivo dose–response curves. The predicted dose–response curves for rat matched available in vivo data on AChE inhibition, and the benchmark dose lower confidence limits for 10% inhibition (BMDL10 values) were in line with the reported BMDL10 values. Humans were predicted to be 6-fold more sensitive than rats in terms of AChE inhibition, mainly because of inter-species differences in toxicokinetics. It is concluded that the TEF-coded DZN PBK model combined with quantitative in vitro to in vivo extrapolation (QIVIVE) provides an adequate approach to predict RBC AChE inhibition upon acute oral DZN exposure, and can provide an alternative testing strategy for derivation of a point of departure (POD) in risk assessment.

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Histamine tachyphylaxis in canine airways despite prostaglandin synthesis inhibition

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.5.1944 ◽

1988 ◽

Vol 65 (5) ◽

pp. 1944-1949 ◽

Cited By ~ 7

Author(s):

P. J. Antol ◽

S. J. Gunst ◽

R. E. Hyatt

Keyword(s):

Smooth Muscle ◽

Dose Response ◽

Prostaglandin Synthesis ◽

Response Curves ◽

Synthesis Inhibition ◽

High Concentrations ◽

Alpha Chloralose ◽

Prostaglandin Synthesis Inhibitors

Tachyphylaxis to aerosolized histamine was studied in dogs anesthetized with thiamylal after pretreatment with prostaglandin synthesis inhibitors. Three consecutive histamine dose-response curves were obtained in nine dogs pretreated with 5 mg/kg indomethacin; two of these nine were also pretreated with 10 mg/kg indomethacin. Seven of the nine dogs were pretreated with 4 mg/kg sodium meclofenamate; four of these seven were also pretreated with 12 mg/kg. All dogs had tachyphylaxis at high concentrations of histamine regardless of inhibitor used. Pretreatment with indomethacin while the dogs were under alpha-chloralose-urethan anesthesia gave similar results. Histamine tachyphylaxis was also studied both in the presence and in the absence of indomethacin in tracheal smooth muscle strips obtained from seven additional dogs. A decrease in the median effective dose to histamine was observed in the indomethacin-treated strips, but tachyphylaxis to histamine remained. We conclude that prostaglandin synthesis inhibition does not reverse histamine tachyphylaxis either in vivo or in vitro. Thus the mechanism of histamine tachyphylaxis remains unexplained.

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Histamine H2-receptor of human and rabbit parietal cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1987.253.4.g497 ◽

1987 ◽

Vol 253 (4) ◽

pp. G497-G501 ◽

Cited By ~ 1

Author(s):

R. Leth ◽

B. Elander ◽

U. Haglund ◽

L. Olbe ◽

E. Fellenius

Keyword(s):

Dose Response ◽

In Vivo Model ◽

Response Curves ◽

Gastric Glands ◽

Histamine H2 Receptor ◽

Receptor Affinity ◽

H2 Receptor ◽

Dose Response Curves

The histamine H2-receptor on the human parietal cell has been characterized by using dose-response curves and the negative logarithm of the molar concentration of an antagonist (pA2) analyses of cimetidine antagonism of betazole, histamine, and impromidine stimulation in isolated human and rabbit gastric glands. To evaluate the in vitro results, betazole-stimulated gastric acid secretion with and without cimetidine was also studied in healthy subjects. In the in vivo model, individual dose-response curves were shifted to the right with increasing cimetidine concentrations, but this was counteracted by increasing betazole doses, indicating competitive, reversible antagonism. The pA2 values ranged from 6.1 to 6.3. In isolated human gastric glands, impromidine was shown to be eight times more potent than histamine, indicating higher receptor affinity, but the maximally stimulated aminopyrine accumulation was the same as for histamine, and the pA2 values for cimetidine antagonism did not differ significantly, i.e., 5.7 (histamine) and 6.1 (impromidine). In isolated rabbit gastric glands, cimetidine inhibited the histamine- and impromidine-stimulated response with pA2 values of 6.0 and 7.3, respectively. Impromidine was shown to be approximately 100 times more potent than in human gastric glands, whereas histamine had the same potency. This confirms the role of the histamine H2-receptor and suggests a difference between the species concerning receptor affinity.

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A Model Mechanism Based Explanation of an In Vitro-In Vivo Disconnect for Improving Extrapolation and Translation

10.1101/216556 ◽

2017 ◽

Author(s):

Andrew K. Smith ◽

Yanli Xu ◽

Glen E.P. Ropella ◽

C. Anthony Hunt

Keyword(s):

Dose Response ◽

Mitochondrial Damage ◽

System Level ◽

Central Vein ◽

Response Curves ◽

Causal Explanations ◽

Dose Response Curves ◽

Virtual Culture

AbstractAn improved understanding of in vivo-to-in vitro hepatocyte changes is crucial to interpreting in vitro data correctly and further improving hepatocyte-based in vitro-to-in vivo extrapolations to human targets. We demonstrate using virtual experiments as a means to help untangle plausible causes of inaccurate extrapolations. We start with virtual mice that have biomimetic software livers. Earlier, using those mice, we discovered model mechanisms that enabled achieving quantitative validation targets while also providing plausible causal explanations for temporal characteristics of acetaminophen hepatotoxicity. We isolated virtual hepatocytes, created a virtual culture, and then conducted dose-response experiments in both culture and mice. We expected the two dose-response curves to be displaced. We were surprised that they crossed because it evidenced that simulated acetaminophen metabolism and toxicity are different for virtual culture and mouse contexts even though individual hepatocyte mechanisms were unchanged. Crossing dose-response curves is a virtual example of an in vivo-to-in vitro disconnect. We use detailed results of experiments to explain the disconnect. Individual hepatocytes contribute differently to system level phenomena. In liver, hepatocytes are exposed to acetaminophen sequentially. Relative production of the reactive acetaminophen metabolite is largest (smallest) in pericentral (periportal) hepatocytes. Because that sequential exposure is absent in culture, hepatocytes from different lobular locations do not respond the same. A virtual Culture-to-Mouse translation can stand as a scientifically challengeable theory explaining an in vitro-in vivo disconnect. It provides a framework to develop more reliable interpretations of in vitro observations, which then may be used to improve extrapolations.AbbreviationsaHPCanalog hepatocyteAPAPacetaminophenCVCentral VeinSSsinusoidal segmentNAPQIN-acetyl-p-benzoquinone iminemitoDmitochondrial damage productsnonMDnon-mitochondrial damage products

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ANG II- and TxA2-induced mesenteric vasoconstriction in rats is mediated by separate cell signaling pathways

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.277.1.h1 ◽

1999 ◽

Vol 277 (1) ◽

pp. H1-H7 ◽

Cited By ~ 5

Author(s):

Johannes Bauer ◽

Cécile Dau ◽

Alessandro Cavarape ◽

Franz Schaefer ◽

Heimo Ehmke ◽

...

Keyword(s):

Signaling Pathways ◽

Dose Response ◽

Ang Ii ◽

Response Curves ◽

Intracellular Ca ◽

The Right ◽

Activate Protein Kinase ◽

Cell Signaling Pathways

Studies in vitro have demonstrated that vasoconstrictor agents increase intracellular Ca2+ and activate protein kinase C (PKC) to elevate vascular tone. The aim of the present study was to determine the importance of these signaling pathways for angiotensin II (ANG II) and thromboxane A2(TxA2) in regulating mesenteric blood flow (MBF) in vivo. In anesthetized rats increasing doses of ANG II or the TxA2 agonist U-46619 were administered into the superior mesenteric artery to reduce MBF. Intra-arterial infusion of inhibitors served to examine the contribution of different pathways: 8-(diethylamino)octyl 3,4,5-trimethoxybenoate hydrochloride (TMB-8) to inhibit intracellular Ca2+ release, nifedipine to block transmembrane Ca2+ influx through the L-type Ca2+ channel, and staurosporine to inhibit PKC. Each of the inhibitors attenuated ANG II-induced reductions in MBF, and all dose-response curves were shifted to the right to an approximately threefold higher ANG II dose. Combinations of the inhibitors revealed that their effects were additive; together they abolished the vasoconstrictor action of ANG II completely. In contrast, the dose-response curve for U-46619 was not affected by any of the inhibitors infused either separately or together. The results demonstrate that a rise in intracellular Ca2+ and activation of PKC are major mediators of the vasoconstrictor effect of ANG II in mesenteric circulation, but they play a subordinate role, if any, for the effects of TxA2. Because TxA2 plays a major role only under pathological conditions, the uncontrolled vasoconstriction appears to be associated with the recruitment of novel signal transduction pathways.

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Nonparallel secretion of GP-2 from exocrine pancreas implies luminal coupling between acinar and duct cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1994.267.1.g40 ◽

1994 ◽

Vol 267 (1) ◽

pp. G40-G51 ◽

Cited By ~ 1

Author(s):

S. D. Freedman ◽

K. Sakamoto ◽

G. A. Scheele

Keyword(s):

Exocrine Pancreas ◽

Acinar Cells ◽

Zymogen Granule ◽

Zymogen Granules ◽

Pancreatic Acini ◽

Glycosyl Phosphatidylinositol ◽

Cellular Processes ◽

Rat Exocrine Pancreas

The in vivo and in vitro secretion of glycoprotein-2 (GP-2), a glycosyl phosphatidylinositol (GPI)-anchored protein from the rat exocrine pancreas, was characterized. GP-2 was secreted in a nonparallel manner compared with amylase, a marker of secretory enzymes. Attenuated GP-2 secretion correlated with hormones that stimulated exocytosis in acinar cells. Augmented GP-2 secretion correlated with hormones that stimulated fluid and bicarbonate secretion from ductal elements. Immunofluorescence studies identified an enriched pool of GP-2 tightly bound to the apical membranes of acinar cells in addition to zymogen granules. This non-zymogen granule pool appears to represent the source of GP-2 released from acinar cells in a nonparallel manner. With the use of dispersed pancreatic acini largely devoid of ductal elements, GP-2 release was found to be augmented by alkaline pH. Thus GP-2 secretion appears to be modulated by two discrete cellular processes: 1) delivery of prereleased GP-2 within zymogen granules to the ductal lumen by exocytic mechanisms and 2) enzymatic release of GPI-anchored GP-2 from the luminal membranes, a kinetic process that appears to be regulated by secretin- or carbachol-induced secretion of bicarbonate.

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Fat-induced changes of the integrity of rat exocrine pancreas measured in vivo and in vitro

Gastroenterology ◽

10.1016/s0016-5085(98)81809-x ◽

1998 ◽

Vol 114 ◽

pp. A448

Author(s):

P. Chowdhury ◽

M. Nishikawa ◽

G.T. Blevins ◽

P.L. Rayford

Keyword(s):

Exocrine Pancreas ◽

Rat Exocrine Pancreas ◽

Induced Changes

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RELEASE OF THYROTROPHIN IN VIVO AND IN VITRO BY SYNTHETIC NEUROHYPOPHYSIAL HORMONES

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y64-009 ◽

1964 ◽

Vol 42 (1) ◽

pp. 75-83 ◽

Cited By ~ 8

Author(s):

Frank S. LaBella

Keyword(s):

Dose Response ◽

In Vitro Release ◽

Optimal Level ◽

Response Curves ◽

Low Concentrations ◽

Pituitary Glands ◽

In Vivo Effects ◽

Synthetic Oxytocin

The influence of synthetic oxytocin and synthetic lysine-8-vasopressin on the release of thyrotrophin (TSH) from slices of the "basophilic" zone of bovine anterior pituitary glands was determined. Up to 10-fold stimulation of TSH release occurred in the presence of the peptide hormones at low concentrations (approximately 10−11 to 10−9 M). Concentrations greater than 10−9 M were less stimulatory, ineffective, or inhibitory. In general, vasopressin stimulated at lower concentrations than did oxytocin. The dose–response curve of oxytocin began to descend at lower concentrations than did that of vasopressin.Stimulation of I131 discharge from the thyroids of propylthiouracil (PTU)-treated, day-old chicks was produced by the intraperitoneal injection of as little as 4 ng vasopressin or 25 ng oxytocin. As the injected dose of either peptide was increased beyond an optimal level, there was less enhancement of I131 discharge, and, with further increases, inhibition. The decreasing response began with lower doses of oxytocin than of vasopressin. The similarities of the dose–response curves of thyroid I131 discharge and of in vitro release of TSH indicate that the in vivo effects of injected neurohypophysial peptides are mediated through the release of endogenous TSH.

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

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.8.3297-3301.2005 ◽

2005 ◽

Vol 49 (8) ◽

pp. 3297-3301 ◽

Cited By ~ 18

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.

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