Effects of intravenously administered Leu- or Met-enkephalin on arterial blood pressure

The purpose of these studies was to determine if two endogenous opioids, leucine (Leu) and methionine (Met) -enkephalin, alter blood pressure and, if so, by what mechanisms. Studies from our laboratory show that intravenous administration of Leu-enkephalin in doses of 0.032–320 μg/kg induced a biphasic response in pentobarbital-anesthetized cats. A transient rise in mean arterial pressure was followed by a more prolonged decline. Administration of Met-enkephalin caused only a decline in mean arterial pressure. Neither agent significantly altered heart rate, venous pressure or the EKG. Having determined that both enkephalins altered blood pressure and observed that the responses were qualitatively different, selected pharmacological antagonists were employed to see if the alterations in blood pressure could be blocked. Naloxone blocked the hypertensive responses and antagonized the hypotensive effects seen with the administration of Leu-enkephalin. Naloxone also shifted the dose-effect curve of Met-enkephalin to the right. Diphenhydramine attenuated both the hypertensive and hypotensive responses of Leu-enkephalin. However, diphenhydramine pretreatment did not alter the decline in blood pressure seen with the higher doses of Met-enkephalin. Propranolol exerted some antagonistic activity in association with the rise in blood pressure seen with Leu-enkephalin, but propranolol did not alter the drop in pressure observed with the administration of either enkephalin. These results show that intravenous administration of the enkephalins can alter blood pressure and these effects are not alike for each enkephalin. Additionally, the enkephalins are not blocked in the same fashion by antagonists, giving support to the hypothesis that the two enkephalins interact with different receptors.     

Pupillary effects of leucine and methionine enkephalin in rats after intraperitoneal administration

Changes in pupil size after peripheral administration of met-enkephalin, leu-enkephalin, or morphine were studied in the rat. With a simple pupillographic technique, the pupil diameter of male, S.D. rats (250–300 g) was measured by a series of photographs taken every 60 sec for at least 45 min after the last drug injection. Morphine (8 mg/kg, SC) caused mydriasis characterized by rapid and marked fluctuations of pupil size. Mydriasis also occurred after leu-enkephalin (5 and 10 mg/kg, IP) and met-enkephalin (20 mg/kg, IP). Both peptides induced morphine-like fluctuations. When given 15 min after morphine, leu-enkephalin (5 and 10 mg/kg) increased the mydriatic effect of morphine from 172 percent of control to 224 and 272 percent, respectively. Met-enkephalin (20 mg/kg, but not 10 mg/kg) also enhanced the mydriatic response of morphine, to 244 percent of control. These interactions appear to represent simple addition rather than potentiation. The effects of both peptides were reversed by naloxone (1 mg/kg, SC), suggesting an opiate receptor interaction for the pupillary effects of the enkephalins. The rat pupil thus provides one of the few in vivo models permitting quantification of enkephalin action after parenteral administration.     

The effects of Δ9-tetrahydrocannabinol Δ9-THC) on the regional concentrations of spermidine in the rat brain

The effects of intravenous administration of Δ⁹-tetrahydrocannabinol (Δ⁹-THC, 2 mg/kg, i.v.) on the regional brain spermidine concentrations of the rat were examined. Thirty minutes after vehicle treatment, the spermidine concentrations were: for the medulla oblongata/pons, 68.2 ± 7.7 μg/g; the hypothalamus, 67.7 ± 2.6 μg/g; the midbrain, 59.1 ± 4.4 μg/g; the cerebellum, 47.3 ± 5.9 μg/g and for the cortex, 13.8 ± 0.8 μg/g. Thirty minutes after Δ⁹-THC, these concentrations were reduced in the midbrain (47.0 ± 8.0% of control, P < 0.0001) and cortex (69.4 ± 7.4% of control, P < 0.009). The spermidine concentrations were not significantly altered in the medulla oblongata/pons (86.5 ± 13.3%, P > 0.36), hypothalamus (107.2 ± 11.8, P > 0.36) or cerebellum (89.0 ± 14.4%, P < 0.48). These results suggest that spermidine within the midbrain and cortex may be involved in the expression of some of the actions of Δ⁹-THC.     

Clinical effects of constant rate infusions of medetomidine–propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery

Background

The aim of the present study was to evaluate clinical efficacy of constant rate infusions (CRIs) of medetomidine–propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery. Thirty horses were sedated intravenously (IV) with medetomidine (6.0 μg/kg) and midazolam (0.02 mg/kg) and induced IV with ketamine (1.0 mg/kg) and propofol (1.0 mg/kg). These horses were randomly allocated to three groups and maintained with sevoflurane and CRI of either medetomidine (3.0 μg/kg/h) (Group M; n?=?10); or medetomidine (3.0 μg/kg/h) and propofol (3.0 mg/kg/h) (Group MP3; n?=?10); or medetomidine (3.0 μg/kg/h) and propofol (6.0 mg/kg/h) (Group MP6; n?=?10). End-tidal sevoflurane concentration (ET_SEVO), cardiovascular parameters, plasma propofol concentration, and recovery time and quality were compared among groups. Data were analyzed by using ANOVA with Tukey’s multiple comparison test, considering P?<?0.05 significant.

Results

ET_SEVO (%) was 2.4?±?0.1 in Group M, 1.7?±?0.2 in Group MP3, and 1.4?±?0.2 in Group MP6; ET_SEVO declined significantly in a propofol-dose-dependent manner. The rates of dobutamine infusion (μg/kg/min) required to keep the mean arterial blood pressure over 70 mmHg were significantly lower in Group MP3 (0.20?±?0.10) and Group MP6 (0.15?±?0.06) than in Group M (0.37?±?0.18). Recovery time and quality did not differ among groups. All horses in Group MP3 required only one attempt to stand, and recovery quality was excellent. Plasma propofol concentrations were stable throughout maintenance of anesthesia in Group MP3, whereas those in Group MP6 increased significantly with increasing duration of maintenance.

Conclusions

CRIs of medetomidine–propofol reduced the sevoflurane requirement for surgical anesthesia as the propofol dose increased, compared with a CRI of medetomidine alone. Additionally, the two propofol protocols provided good maintenance of cardiovascular function. CRIs of medetomidine (3.0 μg/kg/h) and propofol (3.0 mg/kg/h) resulted in excellent-quality recovery. This protocol could therefore be an especially useful additive to sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.

     

Histamine paw edema of mice was increased and became H2-antagonist sensitive by co-injection of nitric oxide forming agents,but serotonin paw edema was decreased

Nitric oxide (NO) suprisingly caused the opposite effect on histamine and serotonin edema. The local injection of acidified nitrite (0.3–30 μg /paw which correspond to 10 μg−1mg/kg) increased histamine edema of mice up to 45±4% and suppressed serotonin edema to 90±3%. Other NO-generators (nitroprusside sodium and hydroxylamine) showed similar effects. These results were in accordance with our previous data on endogenous NO. Methylene blue (MB, 30ng/paw which corresponds to 1 μg/kg) suppressed histamine edema (62±3%) and increased serotonin edema (43±3%) in normal mice, being reversed by acidified nitrite. This suggests the involvement o of guanosine 3′, 5′ -cyclic monophosphate (cGMP) formation for the action of NO. Histamine edema became sensitive to H₂-antagonist, cimetidine, by co-injection of 30 μg/paw (which corresponds to 1mg/kg) acidified nitrite (ED₅₀=30 μg/kg versus ⪢ 1mg/kg). NO seemed to modify the histamine receptor(s) or tautomeric form of histamine. NO, O₂⁻ and other oxyradicals might finely control the vascular permeability together with inflammatory mediators.     

Contamination with ergot bodies (<Emphasis Type="Italic">Claviceps purpurea sensu</Emphasis><Emphasis Type="Italic">lato</Emphasis>) of two horse pastures in Northern Germany

Because the occurrence of Claviceps in European pastures may have been overlooked to cause serious health problem for grazing animals, we documented the degree of Claviceps contamination in two horse pastures and estimated whether the horses could have ingested a critical quantity of alkaloids. We counted the Claviceps sclerotia and determined alkaloid levels using high performance liquid chromatography with fluorescence detection. Depending on the location, the number of sclerotia varied from 0.09 to 0.19 per square meter (central area) and from 0.23 to 55.8 per square meter (border strips). Alkaloid levels in individual sclerotia also varied in different genera of grasses, ranging from 0.98 ± 0.17 μg/kg in Agrostis sp. to 25.82 ± 9.73 μg/kg in Dactylis sp., equivalent to 0.98 μg/kg and 7.26 mg/kg. Sclerotia from Dactylis contained high levels of ergosine (0.209 % ± 0.100 %) and ergocristine (0.374 % ± 0.070 %). Depending on the localization in pastures, alkaloid levels in forage (dry matter, DM) ranged from 16.1 to 45.4 μg/kg in central areas and from 23.9 to 722 μg/kg in border strips. The amount of alkaloids that a horse could have ingested depended on its daily DM uptake, which was higher in the central areas (5.85 kg/day) than in the border strips (2.73 or 0.78 kg/day). In the central areas, this amount of alkaloids ranged from 94.2 to 265.9 μg/day; and in the border strips, from 65.3 (in 2.73 kg DM/day) to as much as 563.8 μg/day (in 0.78 kg DM/day). All these amounts are higher than the European averages for alkaloids ingested by horses via feedstuffs.     

Serum Level of Zinc and Copper in Sudanese Women with Polycystic Ovarian Syndrome

The paper’s objective was to estimate weekly Hg intake from fish meals based on intervention research. Total Hg (THg) concentrations in blood and hair samples collected from men (n = 67) from an intervention study as well as muscular tissues of fresh and after heat-treating fish were determined using the thermal decomposition amalgamation atomic absorption spectrometry method (TDA-AAS) using direct mercury analyzer (DMA-80). The mean of the estimated weekly intake (EWI) was estimated at 0.62 μg/kg bw/week in the range 0.36–0.96 μg/kg body weight (bw) /week through the consumption of 4 edible marine fish species every day (for 10 days) by the participants from the intervention research in Lodz, Poland. The Hg intake in the volunteers in our intervention study accounted for 38.6% of the provisional tolerable weekly intake (PTWI) (1.6 μg/kg bw, weekly) value. The average Hg concentration in the analyzed fish ranged from 0.018 ± 0.006 mg/kg wet weight (Gadus chalcogrammus) to 0.105 ± 0.015 mg/kg wet weight (Macruronus magellanicus). The results for the average consumers were within PTWI of methylmercury (MeHg). Moreover, the average concentration of Hg in the selected fish after heat treatment did not exceed the maximum permitted concentrations for MeHg (MPCs = 0.5 mg/kg wet weight) in food set by the European Commission Regulation (EC/1881/2006). Hence, the risk of adverse effects of MeHg for the participants is substantially low.     

Met-enkephalin: Rapid separation from brain extracts using high-pressure liquid chromatography,and quantitation by binding assay

Met-enkephalin can be rapidly separated with high recovery from leu-enkephalin, -endorphin, and enkephalin metabolites by high-pressure liquid chromatography on a Dupont SCX column. The technique permits separation of endogenous enkephalins from brain extracts for measurement by opiate-receptor binding assay, immunoassay, or for study of the incorporation of radiolabeled amino acids into enkephalin. Using this technique, met-enkephalin was separated from striatal extracts of rats killed by focused microwave irradiation and quantitated by the opiate-receptor binding assay. The concentration of met-enkephalin in the column eluate was 1.3 g/g tissue. This value is comparable to that obtained by radioimmunoassay without purification of the extracts.Pharmacology Research Associate, Pharmacology Research Associate Program, National Institute of General Medical Sciences.     

The production and secretion of cortisol by baboon neonates.

The metabolic clearance rate (MCR), transfer constants (p), production (PR) and secretion (SR) rates of cortisol (F) andrortisone (E) were determined by the continuous infusion of {1,2³H}F and {4-¹⁴C}E into 5 neonates delivered prior to the parturition by cesarean section (164–179 days; term = 184 days) and into 5 newborns delivered spontaneously per vagina at term (166 – 187 days). In spontaneously delivered animals, MCR-E (X ± SE, 34.3 ± 7.0 1/day/kg was greater (P < 0.001) than MCR-F (14.9 ± 1.5 1/day/kg), pF to E (59.7 ± 8.9%) exceeded (P < 0.001) pE to F (17.8 ± 3.0%) and the percentage of F bound to serum proteins other than albumin (57.5 ± 6.2) was greater (P < 0.001) than that of E (27.0 ± 10.3) Although the serum E level (25.6 ± 3.6 μg/100 ml) was similar to that of F (33.5 ± 8.0 μg/100 ml), the PR-E (6.4 ± 1.3 μ/min/kg) was greater (P < 0.001) than PR-F (3.3 ± 0.5 μ/min/kg). Approximately eighty-five percent of the E and 65% of the F produced orginated by secretion.In animals delivered by cesarean section, the serum F concentration (32.4 ± 6.7 μ/100ml), pE to F (13.4 ± 2.8%) pF to E (80.0 ± 12.2%) PR-E (4.5 ± 0.2 μ/min/kg) and SR-E (3.9 ± 0.3 μ/min/kg) were not different from values for spontaneously delivered animals. Serum E levels (35.9 ± 1.6 μ/100 ml) were higher but MCR-F (6.7 ± 0.6 1/day/kg) and MCR-E (18.2 ± 0.41/day/kg) lower in neonates delivered by cesarean section. Serum Cortisol binding capacity (μg F bound/100 ml) was greater (P < 0.025) in neonates delivered by cesarean section (23.6 ± 2.6) than in spontaneously delivered animals (14.4 ± 2.0). As a result of these changes in F and E dynamics, PR-F (1.4 ± 0.3 μ/min/kg) and SR-F (0.9 ± 0.2 μ/min/kg) in neonates delivered by cesarean section were lower (P< 0.01) than corresponding values in spontaneously delivered newborns.It is concluded that the greater F secretion in animals delivered spontaneously than those delivered by cesarean section probably results from increased fetal adrenal 3β-hydroxysteroid dehydrogenase-isomerase activity, which as previously reported, occurs in late gestation in this species.     

Analgesic effect of the midazolam-induced anesthesia in different doses on the patients after the thoracoscopic resection of lung cancer

ObjectiveTo elaborate the analgesic efficiency of midazolam-induced anesthesia in different doses on the patients following the thoracoscopic resection of lung cancer.MethodsNinety patients undergoing thoracoscopic resection of lung cancer between August 2017 and July 2018 were randomized in the observation group (n = 45) and the control group (n = 45). Patients in observation group underwent the anesthesia induced by 0.1 mg/kg midazolam, while for the control group, the dose was adjusted to 0.05 mg/kg. Then, we compared the levels of inflammatory factors, SaO₂, average of arterial pressure and changes in heart rate before and after surgery (48 h) to analyze the efficacy.ResultsAt the postoperative 48 h, patients in the observation group had lower levels of inflammatory factors when comparing with their counterparts in the control group [IL-6, IL-8, IL-1β and TNF-α: (58.44 ± 3.22) μg/L, (2.04 ± 0.26) μg/L, (2.98 ± 0.44) μg/L, (5.33 ± 0.77) μg/L v.s. (96.44 ± 4.54) μg/L, (3.23 ± 0.33) μg/L, (3.77 ± 0.44) μg/L, (7.64 ± 0.99) μg/L] (P < 0.05). Meanwhile, those in the observation group had a lower SaO₂, average arterial pressure and heart rate [(93.79 ± 1.08)%, (93.22 ± 3.46) mmHg, (87.55 ± 2.35) beat/min v.s. (97.13 ± 1.03)%, (96.44 ± 4.03) mmHg, (91.05 ± 2.89) beat/min] (P < 0.05). However, no statistical significance was identified in the differences of the bleeding amount, surgical time and anesthesia time between two groups (P > 0.05), while the eye-opening time and the extubation time in the observation group were all shorter than those in the control group (P < 0.05). Similarly, the postoperative pain scores, total doses of propofol and remifentanil were also lowered (P < 0.05).ConclusionFor patients of thoracoscopic resection of lung cancer, midazolam-induced anesthesia (0.1 mg/kg) performs better than 0.5 mg/kg in inhibiting the inflammatory responses, with significant reduction in the dose of anesthetics, thereby stabilizing the status of patients in perioperative period and mitigating the postoperative pains. Thus, it is potential candidate.     

Cardiac synthesis, processing, and coronary release of enkephalin-related peptides

Although preproenkephalin mRNA is abundant in the heart, the myocardial synthesis and processing of proenkephalin is largely undefined. Isolated working rat hearts were perfused to determine the rate of myocardial proenkephalin synthesis, its processing into enkephalin-containing peptides, their subsequent release into the coronary arteries, and the influence of prior sympathectomy. Enkephalin-containing peptides were separated by gel filtration and quantified with antisera for specific COOH-terminal sequences. Proenkephalin, peptide B, and [Met(5)]enkephalin-Arg(6)-Phe(7) (MEAP) comprised 95% of the extracted myocardial enkephalins (35 pmol/g). Newly synthesized enkephalins, estimated during a 1-h perfusion with [(14)C]phenylalanine (4 pmol x h(-1) x g wet wt(-1)), were rapidly cleared from the heart during a second isotope-free hour. Despite a steady release of enkephalins into the coronary effluent (4 pmol x h(-1) x g wet wt(-1)), enkephalin replacement apparently exceeded its release, and tissue enkephalins actually accumulated during hour 2. In contrast to the tissue, methionine-enkephalin accounted for more than half of the released enkephalin. Chemical sympathectomy produced an increase in total enkephalin content similar to that observed after 2-h control perfusion. This observation suggested that the normal turnover of myocardial enkephalin may depend in part on continued sympathetic influences.     

Selective depression of dopamine-induced depolarization by morphine and enkephalins in snail neurons

Morphine, met-enkephalin, and leu-enkephalin in a concentration of 1×10^?5 M depress rapidly and reversibly the amplitude of depolarization induced by dopamine application toHelix pomatia neurons; the effect is naloxone-dependent. The amplitudes of dopamine-induced hyperpolarization and also of the depolarization and hyperpolarization responses to acetylcholine application are unchanged under these circumstances. The hypothesis of blocking of chemosensitive sodium channels by enkephalins is discussed. It is suggested that this hypothesis is true for high concentrations of morphine and enkephalins (1×10^?4 to 1×10^?3 M). In lower concentrations (1×10^?5 M) morphine and enkephalins lead to modulation of the reponses to the action of neurotransmitters, evidently through their influence on the cyclic nucleotide system.     

Microdialysis and mass spectrometric monitoring of dopamine and enkephalins in the globus pallidus reveal reciprocal interactions that regulate movement

Pallidal dopamine, GABA and the endogenous opioid peptides enkephalins have independently been shown to be important controllers of sensorimotor processes. Using in vivo microdialysis coupled to liquid chromatography-mass spectrometry and a behavioral assay, we explored the interaction between these three neurotransmitters in the rat globus pallidus. Amphetamine (3 mg/kg i.p.) evoked an increase in dopamine, GABA and methionine/leucine enkephalin. Local perfusion of the dopamine D(1) receptor antagonist SCH 23390 (100 μM) fully prevented amphetamine stimulated enkephalin and GABA release in the globus pallidus and greatly suppressed hyperlocomotion. In contrast, the dopamine D(2) receptor antagonist raclopride (100 μM) had only minimal effects suggesting a greater role for pallidal D(1) over D(2) receptors in the regulation of movement. Under basal conditions, opioid receptor blockade by naloxone perfusion (10 μM) in the globus pallidus stimulated GABA and inhibited dopamine release. Amphetamine-stimulated dopamine release and locomotor activation were attenuated by naloxone perfusion with no effect on GABA. These findings demonstrate a functional relationship between pallidal dopamine, GABA and enkephalin systems in the control of locomotor behavior under basal and stimulated conditions. Moreover, these findings demonstrate the usefulness of liquid chromatography-mass spectrometry as an analytical tool when coupled to in vivo microdialysis.     

In Vitro α-Glucosidase Inhibition and Antioxidative Potential of an Endophyte Species (Streptomyces sp. Loyola UGC) Isolated from Datura stramonium L

Endophytic actinomycetes isolated from Datura stramonium L. was evaluated for its effects against in vitro α-glucosidase inhibition, antioxidant, and free radical scavenging activities. Based on microbial cultural characteristic and 16S rRNA sequencing, it was identified as Streptomyces sp. loyola UGC. The methanolic extract of endophytic actinomycetes (MeEA) shows remarkable inhibition of α-glucosidase (IC₅₀ 730.21 ± 1.33 μg/ml), scavenging activity on 2,2-diphenyl-picrylhydrazyl (DPPH) (IC₅₀ 435.31 ± 1.79 μg/ml), hydroxyl radical (IC₅₀ 350.21 ± 1.02 μg/ml), nitric oxide scavenging (IC₅₀ 800.12 ± 1.05 μg/ml), superoxide anion radical (IC₅₀ 220.31 ± 1.47 μg/ml), as well as a high and dose-dependent reducing power. The MeEA also showed a strong suppressive effect on rat liver lipid peroxidation. Antioxidants of β-carotene linoleate model system revels significantly lower than BHA. The total phenolic content of the extract was 176 mg of catechol equivalents/gram extract. Perusal of this study indicates MeEA can be used as natural resource of α-glucosidase inhibitor and antioxidants.     

Modulation of cholinergic neurotransmission in airways by enkephalin

We compared the effects of methionine enkephalin and leucine enkephalin on contractions of isolated canine tracheal smooth muscle strips induced by field electrical stimulation (ES) and exogenous acetylcholine (approximately 10(-5) M). Methionine and leucine enkephalin (10(-8) to 10(-5) M), when added at the peak of airway contractions induced by ES at 1 Hz, depressed the contractions in a concentration-dependent manner by a maximum of 95 and 99%, respectively. Acetylcholine-induced contractions of similar magnitude were depressed only 4% by methionine enkephalin and 12% by leucine enkephalin. Frequency-response curves (0.5-20 Hz) were also obtained before and after incubation of tracheal strips with 10(-5) M methionine and leucine enkephalin. Enkephalin depressed contractions induced by stimulation at 0.5 and 1 Hz by an average of 98 and 95%, respectively. The inhibitory effect of enkephalin progressively decreased at successively higher stimulus frequencies until at 20 Hz there was no significant difference between airway contractions obtained in the presence and absence of enkephalin. Naloxone (3 X 10(-5) M) antagonized the inhibitory effects of both enkephalins. We conclude that methionine and leucine enkephalins inhibit the release of acetylcholine from the postganglionic parasympathetic neurons that innervate airway smooth muscle.     

Comparison of ochratoxin A levels in edible pig tissues and in biological fluids after exposure to a contaminated diet

The aim of this study was to compare ochratoxin A (OTA) levels in pig tissues and biological fluids after animal exposure to contaminated diet (250 μg OTA/kg of feed) during 4 weeks of fattening. OTA concentrations were quantified using a validated immunoassay method (ELISA) and high-performance liquid chromatography with fluorescence detector (HPLC-FD). The highest mean OTA concentration in pig tissues was determined in kidneys of exposed animals (13.87?±?1.41 μg/kg), followed by lungs (10.47?±?1.97 μg/kg), liver (7.28?±?1.75 μg/kg), spleen (4.81?±?0.99 μg/kg), muscle tissue (4.72?±?0.86 μg/kg), fat tissue (4.11?±?0.88 μg/kg), heart (3.71?±?1.09 μg/kg), and brain (3.01?±?0.25 μg/kg). Furthermore, on the last day of exposure (day 28), significantly higher mean OTA levels were determined in urine (16.06?±?3.09 μg/L) in comparison to serum (4.77?±?1.57 μg/L) showing that OTA urine analysis could be a good marker to identify elevated levels of this contaminant in porcine tissues used for human consumption. This study gave guidelines for the most efficient OTA control in pig-derived biological materials that can be exercised at slaughterhouses.     

Increased muscle glucose uptake in response to chronic glyburide treatment is not related to changes in glucose transporter (GLUT4) protein

• 1.1. The mechanism of action of glyburide (a sulfonylurea) on muscle has been investigated by measuring glucose uptake and glucose transporter (GLUT4) protein levels after chronic glyburide treatment.
• 2.2. A dietary induced insulin resistant rat model (4 wk of high-fat, high-sucrose feeding) was given glyburide (2mg/kg/day) for 10 days and glucose uptake was measured in a perfused hindquarter preparation.
• 3.3. Protein levels of the GLUT4 glucose transporter were determined by Western analysis.
• 4.4. After 7 days of treatment, rats fed glyburide had lower blood glucose concentrations 2 hr (72 ± 5 vs 103 ± 12 mg/dl) and 24 hr (97 ± 7 vs 123 ± 7 mg/dl) after glyburide administration with no difference in serum insulin levels compared to vehicle treated animals.
• 5.5. Glucose uptake was approx doubled in basal state (0 insulin) in response to glyburide (2.8 + 0.4 vs 1.7 ± 0.2μ mol/g per hr).
• 6.6. Maximal insulin (100 nM) stimulated glucose uptake tended to be higher in the glyburide treated group, but did not reach statistical significance (8.0 ± 0.7 vs 7.0 ± 0.6 μmol/g per hr).
• 7.7. Western analysis revealed no significant effect of glyburide on the GLUT4 protein level in skeletal muscle.
• 8.8. These results suggest that glyburide alters glucose uptake through some mechanism other than alterations in the level of the GLUT4 glucose transporter protein.

     

Imidazoline receptors of the paraventricular nucleus on the pressor response induced by stimulation of the subfornical organ

In the present experiments we investigated a possible involvement of imidazoline receptors of the paraventricular nucleus (PVN) of the hypothalamus on the pressor effects of the angiotensin II (ANG II) injected into the subfornical organ (SFO), in male Holtzman rats (250–300 g) with a cannula implanted into the third ventricle (3rdV), PVN and SFO. At first we tested the participation of α₂ and imidazoline agonist and antagonist compounds on the pressor effect of ANG II injected into the 3rdV. Based on the results we may conclude that clonidine associated with rilmenidine was able to block the hypertensive response to ANG II. The ANG II (20 pmol) injected into SFO induced a robust increase in blood pressure (37 ± 2 mmHg). Isotonic saline (0.15 M) NaCl did not produce any change in blood pressure (5 ± 2 mmHg). The injection of rilmenidine (30 μg/kg/1 μL), an imidazoline agonist agent injected into PVN before ANG II injection into SFO, blocked the pressor effect of ANG II (5 ± 2 mmHg). Also, the injection of idazoxan (60 μg/kg/μL) before rilmenidine blocked the inhibitory effect of rilmenidine on blood pressure (39 ± 4 mmHg). The injection of clonidine (20 nmol/μL) prior to ANG II into the 3rdV produced a decreased in arterial blood pressure (37 ± 2 mmHg) to (15 ± 4 mmHg). The injection of yohimbine (80 nmol/μL) prior to clonidine blocked the effect of clonidine on the effect of ANG II (27 ± 2 mmHg). The injection of rilmenidine prior to ANG II also induced a decrease in arterial blood pressure (10 ± 3 mmHg). The injection of idazoxan prior to rilmenidine also blocked the inhibitory effect of rilmenidine (24 ± 3 mmHg). In summary, the present study demonstrated that rilmenidine decreases the hypertensive effect of ANG II, with more potency than clonidine, even when injected into 3rdV or PVN. This study established that the PVN interacts with SFO by imidazoline receptors in order to control the arterial blood pressure.     

Cardiovascular effects of peptides related to the enkephalins and β-casomorphin

In the urethane-anesthetized rat, intravenous injections of morphine produced a short-lasting fall in heart rate and blood pressure. The fall in heart rate (which is vagal in origin) was used here to bioassay peptides related to the enkephalins [-enk] and β-casomorphin [β-C, H-Tyr-Pro-Phe-Pro-Gly-Pro-Ile-OH]. A > 10% decrease in heart rate was used as a quantal index of response and the intravenous ED50 [μmol/kg] were estimated as: methionine-enk, 1.3 ± .24; leucine-enk, 1.5 ± .20; [D-Ala², D-Leu⁵]-enk, 0.45 ± .05; [D-Ala², NMePhe⁴, Met(0)⁵-ol]-enk, 0.0011 ± .0002; H-Tyr-Arg-OH, > 2.0; β-C (1–7), > 2.0; β-C(1–5), > 2.0; β-C(1–4), > 4.0; β-C(1–3), > 2.0; morphine sulfate, 0.11 ± .03; and human β-endorphin,, 0.07 ± .01. One β-C derivative, H-Tyr-Pro-Phe-Pro-NH₂ [β-C(1–4)-NH₂], was active at 0.32 ± .08. Naloxone pretreatment blocked the bradycardia produced by the enkephalins and β-C(1–4)-NH₂. The bioassay described here, based on heart rate, may prove to be useful for the rapid detection and estimation of the $\text{in vivo}$ pharmacological activities of new opioid peptides.     

Effect of citrulline on muscle functions during moderate dietary restriction in healthy adult rats

Low calorie diets are designed to reduce body weight and fat mass, but they also lead to a detrimental loss of lean body mass, which is an important problem for overweight people trying to lose weight. In this context, a specific dietary intervention that preserves muscle mass in people following a slimming regime would be of great benefit. Leucine (LEU) and Citrulline (CIT) are known to stimulate muscle protein synthesis (MPS) in post-prandial and post-absorptive state, respectively. This makes them interesting bioactive components to test in the context of dietary restriction. We tested the concept of combining LEU and CIT in adult female rats. We postulated that the sequential administration of LEU (mixed in chow) and CIT (given in drinking water before a rest period) could be beneficial for preservation of muscle function during food restriction. Sixty female rats (22 weeks old) were randomized into six groups: one group fed ad libitum with a standard diet (C) and five food-restricted groups (60 % of spontaneous intake for 2 weeks) receiving a standard diet (R group), a CIT-supplemented diet (0.2 or 1 g/kg/day, CIT0.2 group and CIT1 group, respectively), a LEU-supplemented diet (1.0 g/kg/day) or a CIT + LEU-supplemented diet (CIT + LEU 1.0 g/kg/day each). At the end of the experiment, body composition, muscle contractile properties and muscle protein synthesis (MPS) rate were studied in the tibialis anterior muscle. Dietary restriction tended to decrease MPS (R: 2.5 ± 0.2 vs. C: 3.4 ± 0.4 %/day, p = 0.06) and decrease muscle strength (R: 3,045 ± 663 vs. C: 5,650 ± 661 A.U., p = 0.03). Only CIT administration (1 g/kg) was able to restore MPS (CIT1: 3.4 ± 0.3 vs. R: 2.5 ± 0.2 %/day, p = 0.05) and increase muscle maximum tetanic force (CIT1: 441 ± 15 vs. R: 392 ± 22 g, p = 0.05) and muscle strength (CIT1: 4,259 ± 478 vs. R: 3,045 ± 663 A.U., p = 0.05). LEU had no effect and CIT + LEU supplementation had few effects, limited to adipose mass and fatigue force. The results of this study highlight the ability of CIT alone to preserve muscle function during dietary restriction. Surprisingly, LEU antagonized some effects of CIT. The mechanisms involved in this antagonistic effect warrant further study.