Electronic Library of Scientific Literature



ENDOCRINE REGULATIONS



Volume 31 / No. 3 / 1997




EFFECT OF CALCIUM CHANNEL BLOCKERS ON CHOLESTEROL METABOLISM IN PRAGUE HEREDITARY HYPERCHOLESTEROLEMIC RAT

E. Sebokova, S. Edelsteinova, M. Hromadova, D. Gasperikova, I. Klimes

Diabetes and Nutrition Research Laboratory, Institute of Experimental Endocrinology, Slovak Academy of Sciences, SK-833 06 Bratislava, Slovakia;
Department of Pharmacology & Toxicology, Pharmacological Faculty, Comenius University, SK-832 32 Bratislava, Slovakia

We studied the effect of selected calcium channel blockers (CCB), i.e. verapamil or diltiazem on the activity of LDL receptors (ligand blot) and the hydroxy-methyl-glutaryl coenzyme A reductase (HMG CoA) in the liver, on the content of cholesterol (CH) in the heart, aorta and liver, and on serum levels of total CH, LDL-CH and HDL-CH of 3 months old Prague hereditary hypercholesterolemic (PHHC) rats (which are characterized by CH lipoprotein distribution comparable to that of man, basal hypercholesterolemia and excessive response to CH-rich diet). In the PHHC rats, low HMG CoA reductase activity (PHHC: 88.6±10.2 vs control (C): 199.4±14.0 pmol.min-1.mg-1, P<0.001) and low LDL receptor activity in liver (PHHC: 19.2 ± 1.0 vs C: 100±16.7 %; P<0.001) were accompanied by an increase of total CH content (PHHC: 147.8±9.4 vs C: 8.3±0.6 µmol.g-1; P<0.001) in the liver. This corresponds to differences in serum levels of total CH (PHHC: 7.2±0.6 vs C: 2.0±0.1 mmol.l-1; P<0.001) and LDL-CH (PHHC: 5.9±0.6 vs C: 0.4±0.09 mmol.l-1; P<0.001). CH content in aorta and heart of PHHC rats did not differ from control rats. Both tested CCB showed beneficial effects on the LDL receptor activity (diltiazem: 76.5±8.8 %, P<0.001; verapamil: 48.0±6.7 %, P<0.005), liver CH content (diltiazem: 138.3±6.1, P<0.05; verapamil: 110.2±3.7 µmol.g-1, P<0.01) and serum total CH levels (diltiazem: 4.1±0.4, P<0.001; verapamil: 3.3±0.2 mmol.l-1, P<0.001). The HMG CoA reductase activity in liver and CH content in aorta and heart were not influenced by any of the CCB used. In summary, a) the PHHC rats seem to have a CH clearance defect at the level of liver LDL receptors, b) which can be at least partly overcome by treatment with CCB; c) leading to a reduction of hypercholesterolemia.

Key words: Verapamil Diltiazem Cholesterol Metabolism LDL Receptors Hypercholesterolemia Prague Hereditary Hypercholesterolemic Rat
pp. 123-129

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EFFECTS OF EPIDERMAL GROWTH FACTOR (EGF) ON THYMIDINE KINASE ACTIVITY IN HOMOGENATES OF RAT THYROID LOBES INCUBATED IN VITRO

J. Brzezinski, M. Karbownik, A. Lewinski, H. Modrzejewska, J. Greger

Department of Endocrine Surgery;
Department of Thyroidology, Institute of Endocrinology;
1st Department of Biochemistry, Institute of Physiology and Biochemistry, Medical University of Lodz , Poland

The activity of thymidine kinase (TK - EC 2.7.1.21) was measured in the homogenates of rat thyroid lobes incubated in vitro. This enzyme is responsible for catalyzing the phosphorylation of thymidine and functions as a part of the pyrimidine salvage pathway involved in DNA synthesis. The thyroid tissue was incubated for 4 hours in RPMI 1640 medium (Gibco), containing Hepes buffer, 15 % FCS and the examined substance _ epidermal growth factor (EGF), used in five different concentrations (0.1, 1.0, 10, 100 and 1000 ng/ml). The TK activity was measured by means of Cheng and Prusoff's method (Biochemistry 13, 1179-1185, 1974) as modified by Greger and Draminski (Z. Naturforsch. 44c, 985-991, 1989). The reaction products were separated by ascending chromatography. It was shown that TK activity was suppressed by EGF in all concentrations ttested (P<0.001) and a tendency towards diminishing TK activity could be observed in parallel to increasing EGF concentration. The inhibitory effect of the highest EGF concentration (i.e. 1000 ng/ml) was significantly higher than that of the lowest EGF concentrations (i.e. 0.1 ng/ml, 1.0 ng/ml or 10 ng/ml; P<0.05).

Key words: Rat thyroid Thymidine kinase (EC 2.7.1.21) EGF 4 h-incubation
pp. 131-135

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OXYTOCIN SUPRESSES THE MITOGEN INDUCED ACTIVATION PROCESS OF MURINE B AND T LYMPHOCYTES BUT AUGMENTS THE INTERLEUKIN-2 PRODUCTION

A. Germer, V. Enzmann, K. Droessler

University of Leipzig, Department of Medicine, Paul-Flechsig-Institute of Brain Research, Jahnallee 59, D-04109 Leipzig, Germany,
Institute of Ophthalmology,
Department of Biology, Institute of Zoology

The aim of the study was to evaluate the influence of oxytocin (OT) on the mitogen induced activation process of normal murine splenocytes taken from male CBA mice. For enumerating bioassay antibody and interleukin secreting cells a solid phase enzyme linked immunospot assay (Elispot), for measuring IL-2 a bioassay and for IL-4 an Elisa was used. In the presence of OT (10-5 M or 10-8 M) both the LPS induced differentiation of resting lymphocytes into antibody secreting effector cell and the ConA triggered differentiation into IL-2 or IL-4 secreting cells was significantly decreased when compared with the controls (absence of OT). On the other hand, OT in a concentration of 10-8 M enhanced the intensity of IL-2 synthesis by about four times, while IL-4 synthesis was not altered by this level and only slightly increased by a higher OT concentration (10-5 M). From these results it seems justified to conclude that the effect of OT on lymphocytes at least partly depends on the given status of the cell and the parameter to be measured. Due to the interleukin synthesis OT augments IL-2 but not IL-4.

Key words: Oxytocin Antibody Production Interleukin-2 Interleukin-4 ELISPOT
pp. 137-144

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ELIMINATION OF GLUCAGON AND ADRENALINE RELEASE AND LIVER EFFECT PREVENTS THE INCREASED BILIARY EXCRETION OF rT3 AFTER INSULIN INDUCED HYPOGLYCEMIA IN RATS

P. Langer, K. Gschwendtova

Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia

Three groups of male Wistar rats weighing about 350 g were inserted polyethylene tubings into the bile duct and both femoral veins under pentobarbital anesthesia. After taking first (control) 1-h bile sample individual groups were subjected to following interventions, 1-h bile samples being taken for following 5 h: 1. Group I: 1 ml saline i.v. every hour; 2. Group II: the same treatment with saline as Group I plus infusion of insulin (1 U in 0.5 ml saline for 10 min); 3. Group III: subjected to adrenal medullectomy 2 weeks prior to the experiment (Groups I and II were subjected to sham operation at the same time); on the day of experiment, infused with insulin as Group 2 and, in addition, infused with somatostatin (12 µg in 3.0 ml per 5 h), injected with phentolamine (10 mg/kg) and verapamil (5 mg/kg in 5 doses). Biliary excretion of reverse triiodothyronine (rT3) significantly increased in Group II at 2-4 h after insulin-induced hypoglycemia, while that in controls (Group I) and Group III did not change. It was concluded that the interventions performed in Group III to eliminate the secretion and effect on liver cells of two major counterregulatory hormones (i.e. glucagon and adrenaline) prevented the increased production and release of rT3 during the period of prevailing gluconeogenetic type of glucose production.

Key words: Reverse Triiodothyronine Glucagon Adrenaline Insulin Hypoglycemia Gluconeogenesis
pp. 145-148

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REGULATION OF LUTEINIZATION STIMULATOR SECRETION AND ACTION ON PORCINE GRANULOSA CELLS

M. Jezova, J. Vranova, S. Scsukova, J. Kolena

Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06 Bratislava, Slovakia

Luteinization stimulator (LS) is a nonsteroidal intraovarian factor with stimulatory effects on the differentiation of immatured granulosa cells. The role of phospholipase A2 (PLA2) in the stimulatory action of LS and effect of insulin on LS formation were investigated. Activity of LS was estimated by measuring of progesterone production by immature granulosa cells incubated in the presence of LGC conditioned media and follicular fluid isolated from preovulatory follicles (LFF). A significant stimulation of progesterone production by immature granulosa cells (SGC) in the presence of LFF was observed. On the other hand, LFF inhibited basal and LH+FSH stimulated cAMP production by SGC. PLA2 (0.5 µg.ml-1) decreased the stimulatory effect of LFF. The effect of LFF on progesterone production was not mediated by changes in membrane lipid fluidity. Insulin (I, 5 µg.ml-1), MIX (0.2 mmol.l-1) and forskolin (50 µmol.l-1) significantly enhanced LS formation by LGC. The addition of either MIX or forskolin with insulin to the culture of LGC augmented stimulatory effect of insulin on LS formation. Further addition of dbcAMP (0.1 mmol.l-1) did not alter effect of I+MIX on LS formation by LGC. These results suggest that stimulatory action of insulin on LS secretion is not mediated via cAMP second messenger system.

Key words: Luteinization Stimulator Follicular Fluid Granulosa Cells Progesterone Secretion
pp. 149-155

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EFFECT OF LUTEINIZATION STIMULATOR AND ANDROGENS ON MATURATION OF PORCINE GRANULOSA CELLS

Vranova J., Jezova M., Scsukova S., Kolena J.

Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 83306 Bratislava, Slovak Republic.

Luteinization stimulator (LS), an intrafollicular compound of preovulatory (5-8 mm) follicles, enhanced both basal and gonadotropins-stimulated production of progesterone (P4) by immature granulosa cells. The activity of LS was found in cell conditioned media (CM) obtained after the 3-day cultivation of preovulatory granulosa cells. Influence of testosterone, androstenedione and dihydrotestosterone on LS-enhanced P4 secretion was tested in culture of granulosa cells isolated from small follicles (1-3 mm). Small porcine granulosa cells were cultivated with or without LS in the presence of testosterone, androstenedione and dihydrotestosterone in concentration 10-10, 10-8 and 10-6 mol.l-1. In the absence of LS, P4 production in the media with androgens was not significantly different from controls. LS alone significantly enhanced progesterone production by SGC. Androgens present in the culture media together with LS decreased a stimulatory influence of LS on P4 secretion. These data suggest a possible modulation of granulosa cells maturation by androgens.

Key words: Luteinization Stimulator Androgens Follicular Fluid Progesterone Granulosa Cell Culture
pp. 157-161

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MINIREVIEW
GENE EXPRESSION OF HYPOTHALAMIC PEPTIDES CORTICOTROPIN-RELEASING HORMONE, VASOPRESSIN AND OXYTOCIN DURING STRESS

Skultetyova I., Kiss A., Jezova D.

Institute of Experimental Endocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovakia

pp. 163-172

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