Effects of L-type voltage-gated Ca2+ channel blockade on cholinergic and thermal sweating in habitually trained and untrained men

2020 ◽  
Vol 319 (5) ◽  
pp. R584-R591
Author(s):  
Tatsuro Amano ◽  
Naoto Fujii ◽  
Glen P. Kenny ◽  
Yumi Okamoto ◽  
Yoshimitsu Inoue ◽  
...  
Keyword(s):  
Rectal Temperature ◽  
Low Dose ◽  
Sweat Rate ◽  
Control Site ◽  
Hot Water ◽  
Saline Control ◽  
High Dose ◽  
Voltage Gated ◽  
Sweat Production ◽  
Forearm Skin

We evaluated the hypothesis that the activation of L-type voltage-gated Ca2+ channels contributes to exercise training-induced augmentation in cholinergic sweating. On separate days, 10 habitually trained and 10 untrained men participated in two experimental protocols. Prior to each protocol, we administered 1% verapamil (Verapamil, L-type voltage-gated Ca2+ channel blocker) and saline (Control) at forearm skin sites on both arms via transdermal iontophoresis. In protocol 1, we administered low (0.001%) and high (1%) doses of pilocarpine at both the verapamil-treated and verapamil-untreated forearm sites. In protocol 2, participants were passively heated by immersing their limbs in hot water (43°C) until rectal temperature increased by 1.0°C above baseline resting levels. Sweat rate at all forearm sites was continuously measured throughout both protocols. Pilocarpine-induced sweating in Control was higher in trained than in untrained men for both the concentrations of pilocarpine (both P ≤ 0.001). Pilocarpine-induced sweating at the low-dose site was attenuated at the Verapamil versus the Control site in both the groups (both P ≤ 0.004), albeit the reduction was greater in trained as compared with in untrained men ( P = 0.005). The verapamil-mediated reduction in sweating remained intact at the high-dose pilocarpine site in the untrained men ( P = 0.004) but not the trained men ( P = 0.180). Sweating did not differ between Control and Verapamil sites with increases in rectal temperature in both groups (interaction, P = 0.571). We show that activation of L-type voltage-gated Ca2+ channels modulates sweat production in habitually trained men induced by a low dose of pilocarpine. However, no effect on sweating was observed during passive heating in either group.

scholarly journals Evidence for β-adrenergic modulation of sweating during incremental exercise in habitually trained males

2017 ◽  
Vol 123 (1) ◽  
pp. 182-189 ◽  
Author(s):  
Tatsuro Amano ◽  
Yosuke Shitara ◽  
Naoto Fujii ◽  
Yoshimitsu Inoue ◽  
Narihiko Kondo
Keyword(s):  
Relative Intensity ◽  
Sweat Rate ◽  
Absolute Intensity ◽  
Control Site ◽  
Incremental Exercise ◽  
Saline Control ◽  
Maximum Workload ◽  
Sweat Production ◽  
Adrenergic Mechanism

The aim of the present study was to determine the β-adrenergic contribution to sweating during incremental exercise in habitually trained males. Nine habitually trained and 11 untrained males performed incremental cycling until exhaustion (20 W/min). Bilateral forearm sweat rates (ventilated capsule) were measured at two skin sites that were transdermally administered via iontophoresis with either 1% propranolol (Propranolol, a nonselective β-adrenergic receptor antagonist) or saline (Control). The sweat rate was evaluated as a function of both relative (percentage of maximum workload) and absolute exercise intensities. The sweat rate at the Propranolol site was lower than the control during exercise at 80 (0.57 ± 0.21 and 0.45 ± 0.19 mg·cm−2·min−1 for Control and Propranolol, respectively) and 90% (0.74 ± 0.22 and 0.65 ± 0.17 mg·cm−2·min−1, respectively) of maximum workload in trained males (all P < 0.05). By contrast, no between-site differences in sweat rates were observed in untrained counterparts (all P > 0.05). At the same absolute intensity, higher sweat rates on the control site were observed in trained males relative to the untrained during exercise at 160 (0.23 ± 0.20 and 0.04 ± 0.05 mg·cm−2·min−1 for trained and untrained, respectively) and 180 W (0.40 ± 0.20 and 0.13 ± 0.13 mg·cm−2·min−1, respectively) (all P < 0.05), whereas this between-group difference was not observed at the Propranolol site (all P > 0.05). We show that the β-adrenergic mechanism does modulate sweating during exercise at a submaximal high relative intensity in habitually trained males. The β-adrenergic mechanism may in part contribute to the greater sweat production in habitually trained males than in untrained counterparts during exercise. NEW & NOTEWORTHY We demonstrated for the first time that the β-adrenergic mechanism does modulate sweating (i.e., β-adrenergic sweating) during exercise using a localized β-adrenoceptor blockade in humans in vivo. β-Adrenergic sweating was evident in habitually trained individuals during exercise at a submaximal high relative intensity (80–90% maximal work). This observation advances our understanding of human thermoregulation during exercise and of the mechanism that underlies sweat gland adaptation to habitual exercise training.

Pralidoxime in carbaryl poisoning: an animal model

2007 ◽  
Vol 26 (2) ◽  
pp. 125-129 ◽  
Author(s):  
Maria Mercurio-Zappala ◽  
Jason B. Hack ◽  
Annabella Salvador ◽  
Robert S. Hoffman
Keyword(s):  
Low Dose ◽  
Saline Control ◽  
High Dose ◽  
Test Results ◽  
Exact Test ◽  
Treatment Groups ◽  
Chi Squared ◽  
Block Randomization ◽  
Single Objective

Introduction: Poisoning from organophosphates and carbamates is a significant cause of morbidity and mortality worldwide. Concerns have been expressed over the safety and efficacy of the use of oximes such as pralidoxime (2-PAM) in patients with carbamate poisoning in general, and more so with carbaryl poisoning specifically. The goal of the present study was to evaluate the role of 2-PAM in a mouse model of lethal carbaryl poisoning. Methods: Female ICR Swiss Albino mice weighing 25-30 g were acclimated to the laboratory and housed in standard conditions. One hundred and ten mice received an LD 50 dose of carbaryl subcutaneously. Ten minutes later, they were randomized by block randomization to one of eight treatment groups: normal saline control, atropine alone, 100 mg/kg 2-PAM with and without atropine, 50 mg/kg 2-PAM with and without atropine, and 25 mg/kg 2-PAM with and without atropine. All medications were given intraperitoneally and the atropine dose was constant at 4 mg/kg. The single objective endpoint was defined as survival to 24 hours. Fatalities were compared using a Chi squared or Fisher's exact test. Results: Following an LD50 of carbaryl, 60% of the animals died. Atropine alone statistically improved survival (15% lethality). High dose 2-PAM with and without atropine was numerically worse, but not statistically different from control. While the middle dose of 2-PAM was no different than control, the addition of atropine improved survival (10% fatality). Low-dose 2-PAM statistically improved survival (25% lethality). Atropine further reduced lethality to 10%. Conclusion: When appropriately dosed, 2-PAM alone protects against carbaryl poisoning in mice. Failure to demonstrate this benefit in other models may be the result of oxime overdose. Human & Experimental Toxicology (2007) 26, 125-129

scholarly journals Doxorubicin triggers splenic contraction and irreversible dysregulation of COX and LOX that alters the inflammation-resolution program in the myocardium

2018 ◽  
Vol 315 (5) ◽  
pp. H1091-H1100 ◽  
Author(s):  
Jeevan Kumar Jadapalli ◽  
Griffin W. Wright ◽  
Vasundhara Kain ◽  
Mohammad Asif Sherwani ◽  
Ravi Sonkar ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Structural Changes ◽  
Low Dose ◽  
Chronic Phase ◽  
Saline Control ◽  
Control Group ◽  
High Dose ◽  
Saline Control Group ◽  
Inflammation Resolution ◽  
Acute And Chronic Exposure

Doxorubicin (DOX) is a widely used drug for cancer treatment as a chemotherapeutic agent. However, the cellular and integrative mechanism of DOX-induced immunometabolism is unclear. Two-month-old male C57BL/6J mice were divided into high- and low-dose DOX-treated groups with a maintained saline control group. The first group was injected with a high dose of DOX (H-DOX; 15 mg·kg−1·wk−1), and the second group was injected with 7.5 mg·kg−1·wk−1 as a latent low dose of DOX (LL-DOX). H-DOX treatment led to complete mortality in 2 wk and 70% survival in the LL-DOX group compared with the saline control group. Therefore, an additional group of mice was injected with an acute high dose of DOX (AH-DOX) and euthanized at 24 h to compare with LL-DOX and saline control groups. The LL-DOX and AH-DOX groups showed obvious apoptosis and dysfunctional and structural changes in cardiac tissue. Splenic contraction was evident in AH-DOX- and LL-DOX-treated mice, indicating the systems-wide impact of DOX on integrative organs of the spleen, which is essential for cardiac homeostasis and repair. DOX dysregulated splenic-enriched immune-sensitive lipoxygenase and cyclooxygenase in the spleen and left ventricle compared with the saline control group. As a result, lipoxygenase-dependent D- and E-series resolvin precursors, such as 16HDoHE, 4HDoHE, and 12-HEPE, as well as cyclooxygenase-mediated PG species (PGD2, PGE2, and 6-keto-PG2α) were decreased in the left ventricle, suggestive of defective immunometabolism. Both AH-DOX and LL-DOX induced splenic contraction and expansion of red pulp with decreased CD169+ metallophilic macrophages. AH-DOX intoxicated macrophages in the spleen by depleting CD169+ cells in the acute setting and sustained the splenic macrophage loss in the chronic phase in the LL-DOX group. Thus, DOX triggers a vicious cycle of splenocardiac cachexia to facilitate defective immunometabolism and irreversible macrophage toxicity and thereby impaired the inflammation-resolution program. NEW & NOTEWORTHY Doxorubicin (DOX) triggered splenic mass loss and decreased CD169 with germinal center contraction in acute and chronic exposure. Cardiac toxicity of DOX is marked with dysregulation of immunometabolism and thereby impaired resolution of inflammation. DOX suppressed physiological levels of cytokines and chemokines with signs of splenocardiac cachexia.

scholarly journals Intra-articular Injection of Cell-laden 3D Microcryogels Empower Low-dose Cell Therapy for Osteoarthritis in a Rat Model

2020 ◽  
Vol 29 ◽  
pp. 096368972093214
Author(s):  
Dan Xing ◽  
Wei Liu ◽  
Bin Wang ◽  
Jiao Jiao Li ◽  
Yu Zhao ◽  
...  
Keyword(s):  
Cell Therapy ◽  
Rat Model ◽  
Low Dose ◽  
High Rate ◽  
Saline Control ◽  
High Dose ◽  
Sprague Dawley ◽  
Osteoarthritic Joint

Intra-articular injection of mesenchymal stem cells (MSCs) in an osteoarthritic joint can help slow down cartilage destruction. However, cell survival and the efficiency of repair are generally low due to mechanical damage during injection and a high rate of cell loss. We, thus, investigated an improved strategy for cell delivery to an osteoarthritic joint through the use of three-dimensional (3D) microcryogels. MSCs were seeded into 3D microcryogels. The viability and proliferation of MSCs in microcryogels were determined over 5 d, and the phenotype of MSCs was confirmed through trilineage differentiation tests and flow cytometry. In Sprague Dawley rats with induced osteoarthritis (OA) of the knee joint, a single injection was made with the following groups: saline control, low-dose free MSCs (1 × 105 cells), high-dose free MSCs (1 × 106 cells), and microcryogels + MSCs (1 × 105 cells). Cartilage degeneration was evaluated by macroscopic examination, micro-computed tomographic analysis, and histology. MSCs grown in microcryogels exhibited optimal viability and proliferation at 3 d with stable maintenance of phenotype in vitro. Microcryogels seeded with MSCs were, therefore, primed for 3 d before being used for in vivo experiments. At 4 and 8 wk, the microcryogels + MSCs and high-dose free MSC groups had significantly higher International Cartilage Repair Society macroscopic scores, histological evidence of more proteoglycan deposition and less cartilage loss accompanied by a lower Mankin score, and minimal radiographic evidence of osteoarthritic changes in the joint compared to the other two groups. In conclusion, intra-articular injection of cell-laden 3D microcryogels containing a low dose of MSCs can achieve similar effects as a high dose of free MSCs for OA in a rat model. Primed MSCs in 3D microcryogels can be considered as an improved delivery strategy for cell therapy in treating OA that minimizes cell dose while retaining therapeutic efficacy.

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Regulates Activated Complement C5a in Vivo.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2973-2973
Author(s):  
Toshihiko Nishimura ◽  
Timothy Myles ◽  
Mariko Nagashima ◽  
John Morser ◽  
Ronald G. Pearl ◽  
...  
Keyword(s):  
Low Dose ◽  
Inflammatory Responses ◽  
Pulmonary Inflammation ◽  
Saline Control ◽  
High Dose ◽  
Thrombin Activatable Fibrinolysis Inhibitor ◽  
Cell Counts ◽  
Fibrinolysis Inhibitor ◽  
Anti Inflammatory ◽  
Deficient Mice

Abstract The latent plasma carboxypeptidase thrombin-activatable fibrinolysis inhibitor (TAFI) is activated by thrombin/thrombomodulin on the endothelial cell surface, and functions in dampening fibrinolysis. We recently showed that TAFIa efficiently inactivates bradykinin, C5a, and thrombin-cleaved osteopontin, suggesting that it may have a broad anti-inflammatory role. In this study, we examined the pulmonary inflammatory responses in a C5a-induced alveolitis model in wild-type (WT) and TAFI deficient mice. TAFI deficient mice had been backcrossed into a pure C57/B6 background. C5a was instilled into the trachea of anesthetized mice, which were then allowed to recover. Six hours later, bronchiole alveolar lavage (BAL) was performed and the extent of pulmonary inflammation determined. C5a caused a dose-dependent increase in cell counts (WBC/ul) in the BAL fluids in WT mice (saline control, 5.3±4.1 (mean±SD); C5a at 0.05 mg/ml, 28.7±8.5, C5a at 0.1 mg/ml, 60.4±23.8; n=6 for saline and low-dose C5a, n=12 for high dose C5a; p < 0.0005 and < 0.0001 for low-dose and high-dose C5a compared to saline control respectively). Significantly increased BAL cell counts in the TAFI deficient mice in response to C5a stimulation were noted (saline control, 3.3±3.9; low-dose C5a 70±11.2; high-dose C5a 159.6±58.7; n=6 for saline and low-dose C5a, n=12 for high dose C5a; p < 0.00001 and < 5E-0.6 respectively), representing ~2.4–2.6 fold increase in BAL cell counts in the TAFI deficient mice. Determinations of the wet/dried lung weight ratios, an index of pulmonary edema, showed similarly significant results (WT mice: 4.1±0.14, 4.25±0.1, 4.52±0.15 and TAFI-deficient mice: 4.27±0.41, 5.3±0.53, 5.77±0.62 for saline control, low- and high-dose C5a respectively). Our data indicate that in the absence of TAFI, the chemotactic and inflammatory effects of C5a in pulmonary inflammation were enhanced. We are in the process of testing whether E229K thrombin, which selectively activates protein C and TAFI, will ameliorate the C5a alveolitis response in WT mice. Our results support our thesis that the function of TAFIa is not restricted to fibrinolysis. It has a broad anti-inflammatory role and may serve as a homeostatic counterbalance to thrombin’s inflammatory functions.

Effects of sodium salicylate on physiological responses to work in heat

1964 ◽  
Vol 19 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Eugene D. Jacobson ◽  
David E. Bass
Keyword(s):  
Skin Temperature ◽  
Pulse Rate ◽  
Rectal Temperature ◽  
Temperature Regulation ◽  
Sodium Salicylate ◽  
Sweat Rate ◽  
High Dose ◽  
Desert Environment ◽  
Ambient Conditions ◽  
Hot Environments

The hypothesis was tested that men given sodium salicylate would work in the heat at a lower level of temperature regulation. Healthy young volunteers were exposed to a standardized workload consisting of a 100-min walk at 3.5 mph on a level treadmill. Two ambient conditions were studied: a) simulated desert (120 F D.B., 80 F W.B.) and b) simulated jungle (92 F D.B., 87 F W.B.). Rectal temperature (Tr), skin temperature (Ts), sweat rate ( SR), and pulse rate ( PR) were measured in the subjects during work in the heat under three drug regimens: no drug (control), 0.6 g (low dose), and 7.8 g (high dose). It was found that sodium salicylate had no effect on Ts or PR compared with control; this finding applied to both doses in both hot environments. There was, however, a higher Tr and SR in men who received the high dose of the drug in the tropic environment and an increased SR in the desert climate. There was no decrease in Tr in the desert environment during salicylate administration. The results of this investigation do not confirm the original hypothesis; to the contrary, they suggest that high doses of sodium salicylate potentiates the hyperthermia of unacclimatized men working in the heat. body temperature regulation; exercise; simulated desert environment; simulated jungle environment; hyperthermia; rectal temperature, skin temperature, sweat rate, and pulse rate in hot environments; antipyretics Submitted on August 26, 1963

scholarly journals Cutaneous adrenergic nerve blockade attenuates sweating during incremental exercise in habitually trained men

2018 ◽  
Vol 125 (4) ◽  
pp. 1041-1050 ◽  
Author(s):  
Tatsuro Amano ◽  
Naoto Fujii ◽  
Yoshimitsu Inoue ◽  
Narihiko Kondo
Keyword(s):  
Sweat Rate ◽  
Area Under The Curve ◽  
Incremental Exercise ◽  
Adrenergic Nerves ◽  
Control Treatment ◽  
Adrenergic Nerve ◽  
Saline Control ◽  
Nerve Blockade ◽  
Maximum Workload ◽  
Sweat Production

It remains unknown whether cutaneous adrenergic nerves functionally contribute to sweat production during exercise. This study examined whether cutaneous adrenergic nerve blockade attenuates sweating during incremental exercise, specifically in habitually trained individuals. Accordingly, 10 habitually trained and 10 untrained males (V̇o2max: 56.7 ± 5.4 and 38.9 ± 6.7 ml·kg−1·min−1, respectively; P < 0.001) performed incremental semirecumbent cycling (20 W/min) until exhaustion. Sweat rates (ventilated capsule) were measured at two bilateral forearm skin sites on which either 10 mM bretylium tosylate (BT) (an inhibitor of neurotransmitter release from sympathetic adrenergic nerve terminals) or saline (Control) was transdermally administered via iontophoresis. BT treatment delayed sweating onset in both groups (∼0.66 min; P = 0.001) and suppressed the sweat rate relative to the Control treatment at ≥70% relative total exercise time in trained individuals (each 10% increment; all P ≤ 0.009) but not in untrained counterparts ( P = 0.122, interaction between relative time × treatment). Changes in total sweat production at the BT site relative to the Control site were greater in trained individuals than in untrained counterparts (area under the curve, −0.86 ± 0.67 and −0.22 ± 0.39 mg/cm2, respectively; P = 0.023). In conclusion, we demonstrated that cutaneous adrenergic nerves do modulate sweating during incremental exercise, which appeared to be more apparent in habitually trained men (e.g., ≥70% maximum workload). Although our results indicated that habitual exercise training may augment neural adrenergic sweat production during incremental exercise, additional studies are required to confirm this possibility. NEW & NOTEWORTHY We demonstrated for the first time that cutaneous adrenergic nerves do modulate sweating during high-intensity exercise in humans (≥70% maximum workload). In addition, neural adrenergic sweating appeared to be greater in habitually trained individuals than in untrained counterparts, although further studies are necessary to confirm such a possibility. Nonetheless, the observations presented herein advance our understanding on human thermoregulation while providing new evidence for the neutral mediation of adrenergic sweating during exercise.

Acetaminophen: Neonatal hepatotoxicity due to late pregnancy exposure

1987 ◽  
Vol 45 ◽  
pp. 718-719
Author(s):  
G.A. Miranda ◽  
M.A. Arroyo ◽  
C.A. Lucio ◽  
M. Mongeotti ◽  
S.S. Poolsawat
Keyword(s):  
Low Dose ◽  
Fetal Liver ◽  
Late Pregnancy ◽  
Toxic Chemicals ◽  
Control Group ◽  
High Dose ◽  
Over The Counter ◽  
Liver And Kidney ◽  
Neonatal Liver ◽  
Childbearing Women

Exposure to drugs and toxic chemicals, during late pregnancy, is a common occurrence in childbearing women. Some studies have reported that more than 90% of pregnant women use at least 1 prescription; of this, 60% used more than one. Another study indicated that 80% of the consumed drugs were not prescribed, and of this figure, 95% were “over-the-counter” drugs. Acetaminophen, the safest of all over-the-counter drugs, has been reported to induce fetal liver necrosis in man and animals and to have abortifacient and embryocidal action in mice. This study examines the degree to which acetaminophen affects the neonatal liver and kidney, when a fatty diet is simultaneously fed to the mother during late pregnancy.Timed Swiss Webster female mice were gavaged during late pregnancy (days 16-19) with fat suspended acetaminophen at a high dose, HD = 84.50 mg/kg, and a low dose, LD = 42.25 mg/kg; a control group received fat alone.

Evaluation of hippocampus in rhesus monkeys after chronic (1-year) inhalation exposure to marijuana: I. Electron microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 398-399
Author(s):  
A.M. Andrews ◽  
S.W. Wilson ◽  
A.C. Scallet ◽  
S.F. Ali ◽  
J. Bailey ◽  
...  
Keyword(s):  
Synaptic Vesicles ◽  
Rhesus Monkeys ◽  
Low Dose ◽  
Inhalation Exposure ◽  
Synaptic Cleft ◽  
High Dose ◽  
Withdrawal Time ◽  
Treatment Groups ◽  
Ultrastructural Evidence ◽  
Male Rhesus

Exposure of rhesus monkeys (Macaca mulatta) to marijuana via inhalation or to intravenous delta-9-tetrahydrocannabinol (THC), reportedly caused ultrastructural evidence of increased synaptic width. Chronic marijuana smoke in a single rhesus monkey examined after a six month withdrawal time caused ultrastructure changes in the septal, hippocampal and amygdala regions; the synaptic cleft was widened, electron opaque material was found in the cleft and in the pre- and postsynaptic regions, with some clumping of the synaptic vesicles. The objective of our study was to assess neuropathological alterations produced by chronic inhalation of marijuana smoke.Nineteen male rhesus monkeys, 3-5 years of age and weighing 3-8 kg, were divided into four treatment groups: a) sham control, b) placebo smoke (7 days/ week) c) low dose marijuana (2 times/week with 5 days/week sham) and d) high dose marijuana (7 times/week). A smoke exposure consisted of smoke from one cigarette (2.6% THC) burned down to 10 mm butt length. Smoke was administered via smoke generator (ADL II, Arthur D. Little, Inc. Cambridge, MA) and nose-mouth only masks (local production) equipped with one-way valves.

Benefit/Risk Profile of Combined Antiplatelet Therapy with Ticlopidine and Aspirin

1991 ◽  
Vol 65 (05) ◽  
pp. 504-510 ◽  
Author(s):  
Raffaele De Caterina ◽  
Rosa Sicari ◽  
Walter Bernini ◽  
Guido Lazzerini ◽  
Giuliana Buti Strata ◽  
...  
Keyword(s):  
Platelet Function ◽  
Low Dose ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Stable Coronary Artery Disease ◽  
High Dose ◽  
Single Drug ◽  
Before And After ◽  
Serum Thromboxane ◽  
Artery Disease

SummaryTiclopidine (T) and aspirin (ASA) are two antiplatelet drugs both capable of prolonging bleeding time (BT), with a different mechanism of action. A synergism in BT prolongation has been reported and is currently considered an argument for not recommending their combination. However, a profound suppression of platelet function might be a desirable counterpart of a marked prolongation of BT, with a possible use in selected clinical situations. We therefore studied ex vivo platelet function (aggregation by ADP 0.5-1-2.5 μM; adrenaline 0.75-2.5 μM; collagen 1.5-150 μg/ml; arachidonic acid 1 mM; PAF 1 μM; adrenaline 0.17 μM + ADP 0.62 μM; serum thromboxane ([TX]B2 generation) and BT (Mielke) in 6 patients with stable coronary artery disease receiving such combination. Patients underwent sequential laboratory evaluations at baseline, after 7 days of T 250 mg b.i.d., before and after the intravenous administration of ASA 500 mg, respectively, and, finally, after a minimum of 7 days of sole ASA oral administration (50 mg/day). The experimental design, therefore, allowed a comparison of T and ASA effects (2nd and 4th evaluation), and an assessment of the combination effect (3rd evaluation). Platelet aggregation in response to all doses of ADP was depressed more by T than by ASA. Conversely, responses to adrenaline, and arachidonate were affected more by ASA than by T. For all other agents, differences were not significant. T + ASA combination was more effective (p <0.05) than either treatment alone in depressing responses to high-dose collagen (% over control, mean ± SEM: T: 95 ± 3; ASA: 96 ± 5; T + ASA: 89 ± 4). Serum TXB2 (basal, ng/ml: 380 ± 54) did not change with T (372 ± 36), dropped to <1 ng/ml on ASA injection and slightly re-increased to 9.1 ± 3.1 ng/ml on oral low-dose ASA. BT (basal 7.4 ± 0.6 min) was affected similarly by T (9.2 ± 0.8) or ASA (9.7 ± 0.9) alone, but increased to 15.0 ± 0.7 min on combination treatment (106% increase over control). Thus, the strong synergism in BT prolongation by ASA-T combination has a counterpart in the inhibition of platelet function in response to strong stimuli such as high-dose collagen, not otherwise affected significantly by single-drug treatment. This effect is a possible rationale for the clinical evaluation of T + ASA combination.

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