Volume 33 / No. 2 / 1999
E. Sebokova, D. Gasperikova, M.D. Ouwens, J. Dorrestijn, J. Eckel, A.J. Maassen, I. Klimes
Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia;
Department of Medical Biochemistry, University of Leiden, Leiden, The Netherlands;
Diabetes Research Institute, Düsseldorf, Germany
Objective. To study the regulation of phosphatidylinositol (PI) 3-kinase by insulin in vivo in hereditary hypertriglyceridemic and insulin resistant rat (hHTg).
Methods. Total and insulin receptor substrate-1 (IRS-1) associated PI 3-kinase activities were measured in skeletal muscles and adipose tissue after an intense insulin induced glucose utilization as accomplished by 90 min euglycemic hyperinsulinemic clamp.
Results. In quadriceps femoris muscle, no stimulation of total or IRS-1 associated PI 3-kinase activities was found after hyperinsulinemia in both hHTg and control rats. In contrast, in soleus muscle of control rats total PI 3-kinase activity was stimulated by insulin (P<0.001), while any such effect was not found in hHTg rats. IRS-1 associated PI 3-kinase activity in soleus muscle was significantly decreased in hHTg rats when compared to control rats (P<0.001), but was not affected by insulin. In white adipose tissue (WAT), both the total (P<0.05) and IRS-1 associated PI 3-kinase activities (P<0.001) were increased after 90 min hyperinsulinemia in control animals but not in hHTg animals.
Conclusions. Long-term activation of PI 3-kinase activity by insulin in vivo involves IRS-1 in white adipose tissue, but not in skeletal muscle which implies tissue specificity. The impairment in the PI 3-kinase activation by insulin in hHTg rats may participate in insulin resistance of these animals.
Key words: Insulin - IRS-1 - PI 3-kinase - Insulin resistance - hHTg rat
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T. Mitsuma, N. Rhue, M. Kayama, Y. Mori, K. Adachi, Y. Yokoi, Jing Ping, T. Nogimori, Y. Hirooka
Fourth Department of Internal Medicine and
Department of Laboratory Medicine, Aichi Medical University, Nagakute, Aichi 4801195 Japan and
Department of Internal Medicine, Konanshowa Hospital, Konan, Aichi, Japan
Objective. To investigate the organ distribution of calcium sensing receptor (CaR) in rats by immunohistochemical method.
Methods. CaR was identified immunohistochemically in the rat tissues using specific anti-CaR antiserum raised in New Zealand white rabbits immunized with a conjugate of synthetic CaR peptide (186-204) with bovine serum albumin. Immunohistochemical analysis was performed by avidin-biotin complex method.
Results. CaR immunoreactivity was visualized in the central nervous system, anterior pituitary, gastric mucosa, small intestine and colon, Auerbach,s and Meissner,s gastric nervous branch, small intestine and colon, pancreas, adrenal medulla, kidney and testis. When using antiserum preincubated with synthetic CaR peptide (186-206) or kidney homogenates, no significant stain of kidney was detected.
Conclusions. The findings suggest that CaR is widely distributed and that the method used is valuable in studying the distribution of caR in rat.
Key words: Calcium sensing receptor - Immunohistochemistry - Organ distribution - Rat
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L. Macho, D. Jezova, S. Zorad, M. Fickova
Institute of Experimental Endocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovakia
Objective. To study the basal and ACTH stimulated production of corticosterone by adrenal cortex on one hand and the binding and degradation of corticosterone in the liver of adult rats which were treated with monosodium glutamate (MSG) during the neonatal period.
Methods. Male offsprings of Sprague-Dawley rats were injected i.p. with MSG (4 mg/g of b.w. in saline) on alternated days for the first 10 days of life, their littermates being used as controls. On the 21st postnatal day they were weaned and used for the observation at the age of 65-75 days. After sacrifice the level of corticosterone in serum and the release of corticosterone from incubated adrenals under basal and ACTH stimulated conditions (ACTH in 6 concentrations from 1.25 to 80 mU/ml medium) were estimated. In addition, glucocorticoid binding to cytosol receptors in the liver and muscle tissues was determined. Corticosterone degradation rate was measured by decrease of corticosterone concentration added to the medium after the incubation with liver slices.
Results. Adult rats neonatally treated with MSG had reduced weight of adrenal glands, while plasma corticosterone levels and its basal production by adrenals in vitro were significantly higher than in controls. In MSG treated rats the stimulation of corticosterone production by ACTH was diminished. Glucocorticoid binding to liver cytosolic receptors was significantly decreased, while that in muscle tissue was only slightly elevated. Moreover, a decreased corticosterone degradation rate in liver slices was observed in rats treated neonatally with MSG.
Conclusions. These results are in agreement with previously observed decrease of corticosterone clearance rate in MSG treated animals and suggest that elevated corticosterone levels in plasma and its prolonged response to stressogenic stimulation are due to elevated corticosterone production in adrenals and lower degradation rate in the liver.
Key words: Monosodium glutamate - Rat - Corticosterone metabolism - Adrenals - Liver - Muscle tissue - Receptors
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I. Sabry, L. Al-Ghaith, M. Al-Azemi
Department of Biological Sciences, Faculty of Science, Kuwait University, Safat, 13060 Kuwait
In the present study, the pineal gland of the gerbil Gerbillus cheesmani was described for the first time. According to their electron density, two distinct cell types were observed (light and dark pinealocytes). The nuclei were either oval or irregular. Moderate amount of granular endoplasmic reticulum (GER) was observed. Free ribosomes were present throughout the cytoplasm. Mitochondria and lysosomes were among the most common organelles in the pinealocytes. Several dense core vesicles (DCV) were also noted. Blood capillaries with nonfenestrated endothelium were frequent. Bromocriptine treatment for two weeks influenced, to a degree, the physiology of the pinealocytes. It induced a loss of distinction between light and dark pinealocytes, a decrease in the amount of GER and a reduced frequency of lysosomes. On the contrary, lipid droplets and membrane bound vesicles became more frequent.
Key words: Pineal gland - Gerbil - Ultrastructure - Bromocriptine
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M. Tzaneva, A. Julianov
Department of Pathology,
Department of General Surgery, Medical Faculty, Thracian University, Stara Zagora 6003, Bulgaria
Objective. To examine the number and distribution of chromogranin A, somatostatin and serotonin containing endocrine cells (EC) in the corporal gastric mucosa of patients with Helicobacter pylori (HP) associated chronic gastritis.
Methods. In 12 patients (7 males and 5 females, median age 47 years, range 39-59 years) the number of chromogranin A, somatostatin and serotonin containing endocrine cells (EC) in the corporal gastric mucosa was counted after the appropriate histochemical reaction using specific primary antibodies. The gastric mucosal tissue was obtained by endoscopic biopsy from the greater curvature, anterior and posterior walls of the stomach body. The number of EC was determined per 1 mm2 of the lamina muscularis mucosae.
Results. The number of chromogranin A, somatostatin and serotonin containing EC in the corporal gastric mucosa in the patients examined was not increased.
Conclusions. The lack of changes in the somatostatin containing cells indicates that they are not directly involved in the development of hypergastrinaemia accompanying the HP infection.
Key words: Chromogranin A - Somatostatin - Serotonin - Gastric Endocrine Cells - Helicobacter pylori - Hypergastrinaemia - Chronic Gastritis
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P. Langer, K. Gschwendtová
Institute of Experimental Endocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovakia
Objective. To estimate the excretion of triiodothyronine by bile in groups of rats infused with glucose, arginine or glucose combined with various doses of insulin.
Materials and Methods. Groups of about eight male Wistar Olac rats were anesthetized by pentobarbital and thin polyethylene tubings were inserted into bile duct and femoral vein. The bile was collected into pre-weighed glass vials which were changed every hour. The first one hour interval was considered as control and during the second hour the following i.v. infusions were applied: 1. 2.4 ml 30 % glucose; 2. arginine (80 mg/2.4 ml saline); 3. 2.4 ml 30 % glucose containing 62.5, 125, 250 or 500 mU insulin. In some groups cycloheximide (2.5 mg/kg) or somatostatin (20 microg/kg) were used. The aliquots of bile were treated with beta-glucuronidase/arylsulfatase and the concentration of total (i.e. conjugated plus unconjugated) triiodothyronine was estimated by specific inhouse radioimmunoassay. The results were expressed as ng/hr and the volume of bile was estimated by weighing the previously tared collection vials.
Results. Significant increase of biliary T3 excretion was found during the 60 min infusion of glucose or arginine. However, in fed rats such increase did not continue after the termination of infusion, while in fasted rats the increase was observed still for next 60 min after the infusion. The attempts to further stimulate the excretion of T3 by the addition of small insulin doses (62.5, 125, 250 and 500 mU) to the infused glucose showed inversed effect: by such intervention the increase of T3 was blunted by higher doses, while at lower doses unsignificant increase appeared. The increase of biliary T3 excretion was also blunted by cycloheximide (translation inhibitor) and somatostatin (insulin release inhibitor) both in normal fed and 24 hr fasted rats.
Conclusions. Short-term i.v. infusion of glucose and arginine resulted in immediate and transient increase of biliary T3 excretion which was inhibited by both the cycloheximide and somatostatin. Taken together with our previous findings, this supports the view on rapid fluctuation of hepatic iodothyronine metabolism as related to preprandial (prevailing effect of gluconeogenetic hormones resulting in preferential formation of rT3) and postprandial period (predominant effect of insulin resulting in preferential formation of T3).
Key words: Biliary triiodothyronine - Glucose - Arginine - Insulin - Iodothyronine metabolism - Liver - Cycloheximide - Somatostatin
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Z. Kostecka, J. Blahovec
University of Veterinary Medicine, Department of Chemistry, Biochemistry and Biophysics, 041 81 Kosice, Slovakia
Insulin-like growth factor (IGF) action is influenced by the insulin-like growth factor binding proteins (IGFBPs). Since 1988 eight forms of IGFBPs have been found which differ in molecular weight, amino acid composition, distribution in biological fluids and influence upon IGF activity. An important biological property of the IGFBPs is their ability to increase the halflife of the IGFs in the blood. They are able to act as potentiators of IGFs activity on the cell proliferation. As IGFBPs bind to cell surfaces, they may act either to deliver the IGFs to those surfaces either for the activation of specific receptors or cell responses independently of receptor activation. Posttranslation modification such as phosphorylation, glycosylation and proteolysis of IGFBPs influence their affinity to IGFs. In addition, the IGFBPs may also act as inhibitors to block the activity of the IGFs by preventing cellsurface binding.
Key words: IGF - IGF binding proteins - Receptors - Minireview
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