Forskolin stimulation of naphthylamidase in guinea pig thyroid sections detected with a cytochemical bioassay

1985 ◽  
Vol 108 (3) ◽  
pp. 367-371 ◽  
Author(s):  
Patricia A. Ealey ◽  
Leonard D. Kohn ◽  
Nicholas J. Marshall ◽  
Roger P. Ekins
Keyword(s):  
Guinea Pig ◽  
Dose Response ◽  
Response Curve ◽  
Thyroid Tissue ◽  
Receptor Site ◽  
Dose Response Curve ◽  
Cytochemical Bioassay ◽  
Surface Receptor ◽  
Stimulation Of ◽  
Endocrine Tissues

Abstract. Forskolin, from the roots of the Indian medicinal plant Coleus forskohlii, has recently been shown to be a potent stimulator of adenylate cyclase in many systems, including endocrine tissues such as the thyroid gland. We describe forskolin activation of β-naphthylamidase activity in guinea pig thyroid tissue using the cytochemical bioassay (CBA) for thyroid stimulators. This CBA is the most sensitive bioassay for TSH and LATS-B currently available, being able to detect stimulation by doses as low as 10−5 mU TSH/l and 10−9 mU LATS-B/l. The dose-response curve to forskolin was bell-shaped (as is seen with TSH and LATS-B) with the ascending limb of the curve produced by 10−13 m to 10−12 m forskolin after a 3 min exposure time. Maximal stimulation was observed with 10−12m forskolin. However, the dose-response curve to forskolin was not parallel to that given by TSH, the slope of the ascending limb being much greater. It has been suggested that stimulation of β-naphthylamidase activity in the CBA is via cAMP. We report that dibutyryl cAMP at doses from 10−16m to 10−11 m produces a bell-shaped dose-response curve with a very broad peak response, again not parallel to that produced by TSH. Forskolin activation of β-naphthylamidase in the CBA is unaffected by a 1:106 dilution of 11E8, a monoclonal antibody raised against solubilised TSH receptors, which binds to the TSH receptor and inhibits TSH stimulation. Although the precise location of forskolin action is not known, this is further evidence that forskolin acts at a post-surface receptor site.

VIP stimulation of β-naphthylamidase activity in guinea-pig thyroid sections

1985 ◽  
Vol 109 (4) ◽  
pp. 505-510 ◽  
Author(s):  
P. A. Ealey ◽  
N.J. Marshall ◽  
R. P. Ekins
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Receptor Site ◽  
Dose Response Curve ◽  
Tsh Receptor ◽  
Maximal Response ◽  
Cytochemical Bioassay ◽  
Order Of Magnitude ◽  
Specific Receptors ◽  
Stimulation Of

Abstract. Subsequent to the discovery of vasoactive intestinal peptide (VIP) in the thyroid gland, VIP has been shown to stimulate various thyroid functions. The site of interaction of VIP with the thyroid follicular cell is at present not known, and this study has used the ultrasensitive cytochemical bioassay (CBA) for thyroid stimulators to investigate this further. Exposure of thyroid sections for 3 min to VIP resulted in increased naphthylamidase activity, with half-maximal response observed at 3 × 10−13 m VIP. This response to such low doses of VIP is consistent with the CBA being ultrasensitive to other thyroid stimulators e.g. TSH, thyroid stimulating antibodies and forskolin. The response to VIP was abolished by rabbit anti-VIP antiserum. The dose-response curve to VIP was bell-shaped (as with the other stimulators), maximal stimulation occurring at 10−12 m VIP. In contrast, however, to other thyroid stimulators, namely TSH, LATS-B and 3 monoclonal stimulating antibodies, whose ascending limbs of the doseresponse curves extended over 3-4 orders of magnitude, the VIP curve rose rapidly from basal to maximal tissue stimulation from 10−13 to 10−12m VIP, i.e. one order of magnitude. This unusual dose-response curve to VIP was parallel to that produced by forskolin. 11E8, a monoclonal 'blocking' antibody which is a potent inhibitor of TSH stimulation, did not 'block' forskolin stimulation, consistent with the belief that forskolin acts at a post-receptor site. However, unlike forskolin, VIP was inhibited by monoclonal 11E8, which may imply a hitherto unexpected involvement of the TSH receptor in VIP stimulation of the thyroid or, alternatively, steric inhibition by 11E8 when bound to the TSH receptor of VIP interaction with adjacent VIP-specific receptors.

Secretagogue stimulation of [14C]aminopyrine accumulation by isolated canine parietal cells

1980 ◽  
Vol 238 (4) ◽  
pp. G366-G375 ◽  
Author(s):  
A. H. Soll
Keyword(s):  
Parietal Cell ◽  
Dose Response ◽  
Response Curve ◽  
Dissociation Constants ◽  
Receptor Site ◽  
Dose Response Curve ◽  
Cell Content ◽  
Parallel Displacement ◽  
Mucosal Cells ◽  
Stimulation Of

Isolated canine gastric mucosal cells accumulate [14C]aminopyrine (AP) when treated with histamine, gastrin, and carbachol. In fractions of varying parietal cell content, this accumulation of AP correlated with the parietal cell content. Cimetidine caused parallel displacement of the dose-response curve to histamine, but failed to alter the response to carbachol or gastrin. Atropine caused parallel displacement of the dose-response curve to carbachol, but failed to inhibit the response to histamine or gastrin. The dissociation constants (Kb) for cimetidine inhibition of histamine and for atropine inhibition of carbachol were found to be 1.0 micro M and 1.3 nM, respectively, values comparable to those reported for other tissues. Thus, the isolated parietal cell appears to have pharmacologically typical H2- and muscarinic receptors, with gastrin acting at a third receptor site. Isobutyl methylxanthine (IMX) and the cAMP analogues dibutyryl cAMP (DBcAMP) and 8-bromo cAMP (but not the same analogues of cGMP) also stimulated AP accumulation. Atropine failed to inhibit the responses to IMX or DBcAMP, whereas cimetidine did inhibit the response to IMX, but not to DBcAMP.

Effects of inhibitors of cyclic nucleotide phosphodiesterase on actions of cholecystokinin, bombesin, and carbachol on pancreatic acini

1983 ◽  
Vol 245 (5) ◽  
pp. G676-G680
Author(s):  
J. D. Gardner ◽  
V. E. Sutliff ◽  
M. D. Walker ◽  
R. T. Jensen
Keyword(s):  
Dose Response ◽  
Cyclic Nucleotide ◽  
Response Curve ◽  
Dose Response Curve ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Rightward Shift ◽  
Stimulation Of

In dispersed acini from guinea pig pancreas two inhibitors of cyclic nucleotide phosphodiesterase, Ro 20-1724 and 3-isobutyl-1-methylxanthine (IBMX), augmented the increase in amylase secretion caused by supramaximal concentrations of cholecystokinin but did not alter the stimulation of enzyme secretion caused by bombesin. The augmentations of the action of cholecystokinin caused by Ro 20-1724 or IBMX could be reproduced by 8-bromo-cAMP. When tested alone or with theophylline, cholecystokinin did not alter cAMP in pancreatic acini; however, with Ro 20-1724 or IBMX, concentrations of cholecystokinin that were supramaximal for stimulating amylase secretion caused a significant increase in cellular cAMP. These findings indicate that Ro 20-1724 and IBMX augment the action of cholecystokinin on enzyme secretion by inhibiting cyclic nucleotide phosphodiesterase and allowing a significant cholecystokinin-induced increase in cellular cAMP. IBMX but not Ro 20-1724 caused a parallel rightward shift in the dose-response curve for the stimulation of amylase secretion caused by carbachol. IBMX also caused a parallel rightward shift in the dose-response curve for the stimulation of outflux of 45Ca caused by carbachol. These results indicate that IBMX, but not Ro 20-1724, can function as a muscarinic cholinergic antagonist.

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.

Blockade of histamine-induced contractions of guinea pig ileum by β-haloalkylamines

1976 ◽  
Vol 54 (3) ◽  
pp. 386-392 ◽  
Author(s):  
T. P. Kenakin ◽  
D. A. Cook
Keyword(s):  
Guinea Pig ◽  
Dose Response ◽  
Response Curve ◽  
Longitudinal Muscle ◽  
Sodium Thiosulfate ◽  
Dose Response Curve ◽  
Maximum Response ◽  
Guinea Pig Ileum ◽  
Parallel Shift ◽  
Higher Doses

In the longitudinal muscle strip of guinea pig ileum phenoxybenzamine (POB) produces a maximum parallel shift of 0.7 log units in the dose–response curve to histamine. In the presence of sodium thiosulfate in the wash fluid the parallel shift with retention of maximum response increases to about 2 log units, and a similar value is obtained for N-ethyl-N-(2-bromoethyl)-1′-naphthylamine. The agent N-ethyl-N-(2-chloroethyl)benzylamine produces a significantly smaller shift of dose–response curve of 1.53 log units before the maximum response becomes depressed. The receptor-specific depression of maximum response produced by higher doses of POB is reversed by sodium thiosulfate and by bovine serum albumin, while the parallel shift in dose–response curve is unaffected by both treatments. These findings may be explained by a hypothesis involving interaction of 2-haloalkylamines at two sites.

Calcium antagonists and contractile responses in rat vas deferens and guinea pig ileal smooth muscle

1979 ◽  
Vol 57 (8) ◽  
pp. 804-818 ◽  
Author(s):  
C. R. Triggle ◽  
V. C. Swamy ◽  
D. J. Triggle
Keyword(s):  
Guinea Pig ◽  
Dose Response ◽  
Calcium Antagonists ◽  
Response Curve ◽  
Vas Deferens ◽  
Contractile Activity ◽  
Rat Vas Deferens ◽  
Dose Response Curve ◽  
Tonic Component ◽  
High K

The effect of depletion of extracellular Ca2+ (Ca2+ext) on the loss of responsiveness of the guinea pig ileal longitudinal muscle (g.p.i.l.m.) and the rat vas deferens (r.v.d.) to K+ and cis-2-methyl-4-dimethylaminomethyl-1,3-dioxolane methiodide (CD), and K+ and noradrenaline (NA), has been examined and compared with the effects of a variety of local anesthetics and calcium antagonists. The results indicate that qualitative similarities are apparent with respect to the dependence of agonist-induced activity on Ca2+ext in both the g.p.i.l.m. and r.v.d. Distinct differences, however, in the Ca2+ translocation processes in these two tissues, in response to the different agonists, can be shown by the use of a variety of 'calcium antagonists' thus indicating that such translocation processes are both tissue and agonist selective.It is thus noted that, contrary to the Ca2+ depletion studies, D 600 and the usually more potent BAY-1040 showed no discrimination of action or potency in their ability to inhibit components of the NA response in the r.v.d. In contrast, D 600 and the more potent BAY-1040 selectively inhibited the tonic component of the K+ response. Treatment with SKF 525A and parethoxycaine (PC) in the g.p.i.l.m. and SKF 525A in the r.v.d. resulted in a nonselective inhibition of responses of the tissues to all stimulants. However, in the r.v.d. PC potentiated NA action, and its methobromide (MeBr) derivative potentiated both NA and K+ action and also, like PC, partially shifted to the left the dose-response curve to Ca2+ in NA-depolarizing Ca-free Tyrode's. The quaternary MeBr and the tertiary 2-chloroethyl (2Cl) derivatives of SKF 525A and PC were selectively more effective against CD- than K+-supported contractile activity in the g.p.i.l.m. and the 2Cl derivatives were more effective against NA than K+ responses in the r.v.d. The 2Cl derivative of PC also was more effective in antagonizing the Ca2+ dose–response curve in high-CD or high-NA than in high-K+ Ca2+-free Tyrode's.

2-Chloroadenosine increases calcium mobilization from mouse calvaria in vitro

1982 ◽  
Vol 100 (2) ◽  
pp. 313-320 ◽  
Author(s):  
Ulf Lerner ◽  
Bertil B. Fredholm
Keyword(s):  
Bone Resorption ◽  
Cyclic Amp ◽  
Bone Tissue ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Cyclic Amp Accumulation ◽  
Adenosine Analogue ◽  
Stimulation Of

Abstract. The effect of 2-chloroadenosine on bone resorption and on cyclic AMP formation in murine calvarial bones in vitro was investigated. 2-Chloroadenosine increased the release of 45Ca from the cultured bones, but had no effect on dead bones, indicating that the effect is cell mediated. The adenosine analogue remained in the medium for 48 h and caused a transient stimulation of the formation of cyclic AMP. The dose-response curve for the stimulatory effect on cyclic AMP accumulation was linear up to 10−4m. The dose-response curve for 45Ca release was linear from 3 × 10−7 m to 3 × 10−5 m but then showed a decline in the response. 8-Bromo cyclic AMP inhibited the release of 45Ca in 24 h cultures. The initial stimulatory effect on bone resorption by 2-chloroadenosine may therefore not depend on cyclic AMP. The level of inosine increased during culture indicating that adenosine is formed by bone tissue.

Effects of inhibitors of cyclic nucleotide phosphodiesterase on the actions of vasoactive intestinal peptide and secretin on pancreatic acini

1982 ◽  
Vol 242 (6) ◽  
pp. G547-G551
Author(s):  
J. D. Gardner ◽  
L. Y. Korman ◽  
M. D. Walker ◽  
V. E. Sutliff
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Dose Response ◽  
Cyclic Nucleotide ◽  
Response Curve ◽  
Phosphodiesterase Inhibitor ◽  
Dose Response Curve ◽  
Cyclic Nucleotide Phosphodiesterase ◽  
Amylase Secretion ◽  
Pancreatic Acini ◽  
Stimulation Of

Theophylline, 3-isobutyl-1-methylxanthine (IBMX), and Ro 20-1724 each augmented the increase in cAMP and the stimulation of amylase secretion caused by vasoactive intestinal peptide (VIP) or secretin. With IBMX the dose-response curve for the stimulation of amylase secretion caused by VIP or secretin spanned a range of lower concentrations than did that obtained with Ro 20-1724, which in turn spanned a range of lower concentrations than did that obtained with theophylline. The configuration of the dose-response curve for the action of VIP on cAMP differed with each phosphodiesterase inhibitor tested. With Ro 20-1724 the dose-response curve was monophasic, whereas with the two methylxanthines the dose-response curve was biphasic. With theophylline the magnitude of the second component of the dose-response curve was larger than the first; with IBMX the magnitude of the first component was larger than the second. The configuration of the dose-response curve for the action of secretin on cAMP also differed with each phosphodiesterase inhibitor tested. With theophylline the dose-response curve was monophasic, whereas with Ro 20-1724 and IBMX the dose-response curve was biphasic. With Ro-20-1724 the magnitude of the second component of the dose-response curve was larger than the first; with IBMX the magnitude of the first component was larger than the second. These results indicate that cAMP is compartmentalized in pancreatic acinar cells and that the different compartments of cAMP are affected differently by various inhibitors of cyclic nucleotide phosphodiesterase. These findings also suggest that the different compartments of cAMP are acted on by phosphodiesterases with different sensitivities to various inhibitors.

Responses of airway rapidly adapting receptors to bradykinin before and after administration of enalapril in rabbits

1992 ◽  
Vol 83 (4) ◽  
pp. 399-407 ◽  
Author(s):  
M. Hargreaves ◽  
K. Ravi ◽  
M. P. J. Senaratne ◽  
C. T. Kappagoda
Keyword(s):  
Dose Response ◽  
Neural Activity ◽  
Response Curve ◽  
Enzyme Inhibitor ◽  
Dose Response Curve ◽  
Receptor Activity ◽  
Before And After ◽  
Resting Activity ◽  
Control State ◽  
Stimulation Of

1. The present study was performed in anaesthetized, artificially ventilated, open-chested rabbits to examine whether (a) the rapidly adapting receptors of the airways were stimulated by exogenously administered bradykinin, and (b) if this sensitivity could be enhanced by the angiotensin-converting-enzyme inhibitor, enalapril. 2. Rapidly adapting receptor activity (n = 8) was recorded from the cervical vagus. Bradykinin was injected intravenously (0.25–1.0 μg/kg) and a dose—response curve relating receptor activity to bradykinin was elicited. In the control state, the threshold dose of bradykinin required for stimulation of rapidly adapting receptors was 0.53 ± 0.11 μg/kg. Five minutes after the administration of enalapril maleate (2 mg intravenously), the dose—response curve was shifted to the left significantly (P<0.01). 3. In seven other rapidly adapting receptors, enalapril (2 mg) increased the resting activity significantly (P<0.05) over a period of 60 min. This increase was significantly different from the spontaneous variation in neural activity of rapidly adapting receptors (n = 7) recorded over a period of 60 min. 4. Bradykinin either alone (0.25–1.0 μg/kg) or in the presence of enalapril did not stimulate the slowly adapting receptors (n = 5) of the airways. 5. These results show that (a) exogenous bradykinin stimulates the rapidly adapting receptors, (b) the sensitivity of rapidly adapting receptors to bradykinin is enhanced by enalapril and (c) enalapril increases the resting activity of rapidly adapting receptors. It is suggested that the cough reported after the administration of enalapril may be due to stimulation of rapidly adapting receptors of the airways.

The Blockade of Angiotensin Action by 8-Leu-Angiotensin on the Guinea-Pig Aortic Strip

1974 ◽  
Vol 52 (2) ◽  
pp. 236-239 ◽  
Author(s):  
P. LeMorvan ◽  
Dj. Palaic ◽  
W. K. Park
Keyword(s):  
Angiotensin Ii ◽  
Guinea Pig ◽  
Dissociation Constant ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Apparent Dissociation Constant ◽  
Aortic Strip ◽  
Potent Antagonist ◽  
The Right

The action of angiotensin on the isolated guinea-pig aortic strip is shown in relation to other agonists. The apparent dissociation constant for angiotensin, as calculated from the dose–response curve, is 6.3 × 10−8 M. The blocking action of 8-Leu-angiotensin II on this preparation is specific for angiotensin since responses to other agonists are not modified. Complete reversibility of the blockade is demonstrated. A parallel shift to the right of the dose–response curve and attainment of maximum response indicate that the antagonism is competitive for angiotensin. It is concluded that 8-Leu-angiotensin II is a highly potent antagonist for angiotensin in this tissue.

Sign in / Sign up

Export Citation Format

Share Document