Electronic Library of Scientific Literature



ENDOCRINE REGULATIONS



Volume 32 / No. 3 / 1998




SEARCH FOR EXTRAPANCREATIC EFFECTS OF NEW ORAL HYPOGLYCEMIC AGENT A-4166: 1. ORAL GLUCOSE TOLERANCE TESTS IN NORMAL AND HEREDITARY INSULIN RESISTANT RATS

I. Klimes, E. Sebokova, D. Gasperikova, A. Mitkova, S. Kuklova, P. Bohov, J. Stanek

Diabetes and Nutrition Research Group, Institute of Experimental Endocrinology, Slovak Academy of Sciences, 83306 Bratislava, Slovakia;
Clinic of Gastroenterology, Institute of Postgraduate Medical Education, Bratislava

Objective. To test the effect of new oral hypoglycemic compound A-4166 on insulin secretion during oral glucose challenge in normal and hereditary non-obese, hypertriglyceridemic, insulin resistant and hypertensive rats fed either a normal or high fat diet.
Methods. The rats used were 15 weeks old males of Wistar Charles River strain (controls) and Wistar-derived hereditary hypertriglyceridemic (hHTg) rats of our own colony. They were fed either basal (12 cal% of fat) or high fat diet (70 cal% fat). After 3 weeks of feeding the above diets, the oral glucose tolerance tests (2 g/kg) were carried out in unrestrained conscious rats kept in special metabolic cages after overnight fasting and ten minutes after the administration of A-4166 (100 mg/kg) or placebo by the stomach tube. Plasma glucose, triglycerides, free fatty acids and insulin levels were measured by routine analytical methods.
Results. High fat diet feeding resulted in an increase in fasting plasma insulin in both rat strains, while fasting plasma glucose in high fat diet fed animals remained unchanged as compared to those fed basal diet. No differences in the fasting FFA levels were found. The glucose area under curve (AUC) did not differ between the two strains used and high fat diet resulted in a higher glucose AUC in both strains. The administration of A-4166 improved the glucose tolerance in all animals, namely in those fed the basal diet. Insulin AUC showed very similar pattern in both rat strains proving the stimulatory effect of A-4166 on insulin secretion during an oral glucose challenge. High fat feeding resulted in an impairment of insulin action, but the administration of A-4166 restored the antilipolysis in both strains to the normal range.
Conclusions. The previously reported hypoglycemic action of A-4166 resulting from the increased insulin secretion was confirmed. Moreover, some beneficial action of A-4166 on antilipolysis in vivo was demonstrated.

Key words: Insulin - OGTT - Glucose - FFA - Hereditary insulin resistant rats - Hypoglycemic drug A-4166 -High fat diet
Endocrine regulations, Vol. 32, 115 - 123, 1998

Download full text in PDF format (166 kB)


INFLUENCE OF ETHYNODIOL DIACETATE ON THE FORMATION OF A-HOMO-3-OXA-5alpha-PREGNANE-4,20-DIONE IN FEMALE RATS

B. Simic, J. Kniewald, Z. Kniewald

Faculty of Food Technology and Biotechnology, University of Zagreb, 10000 Zagreb, Croatia

Objective. To give more insight in the progesterone metabolism in rat after the treatment with the progestin ethynodiol diacetate.
Methods. Urinary excretion of the metabolites of subcutaneously administred (4-14C)-progesterone was studied in female rats. After an acid hydrolysis and extraction of urine the metabolites were analysed by thin layer chromatography and by gas chromatography-mass spectrometry.
Results. The most of radioactivity was excreted during the first 24 h, and total of 8.36 % has been recovered within four days. The excreted metabolites in urine were found as glucuronides and free steroids (80.72 %), and 19.28 % were determined as sulphates. Among detected metabolites, 5alpha-pregnane-3,20-dione, 3alpha-hydroxy-5alpha-pregnan-20-one and A-homo-3-oxa-5alpha-pregnane-4,20-dione were determined in the urinary extracts. The last one has not yet been identified before in rat urine.
Conclusions. Consecutive injections of progestin ethynodiol diacetate (6 mg/kg b.w. daily) to adult female rats during 10 days (short-term treatment), or during 70 days (long-term treatment), starting on the 21st day of life, caused significant differences in the amounts of excreted 3alpha-hydroxy-5alpha-pregnan-20-one and A-homo-3-oxa-5alpha-pregnane-4,20-dione. Significant increase in the weights of pituitary, liver and kidneys were noted in rats treated with ethynodiol diacetate. The short-term treatment caused an increase, while after the long-term treatment a decrease of the ovarian weight was observed.

Key words: Progesterone metabolites - Rat - Urine - Ethynodiol diacetate - Gas chromatography - Mass spectrometry
Endocrine regulations, Vol. 32, 125 - 131, 1998

Download full text in PDF format (88 kB)


EARLY POSTNATAL GLUTAMATE TREATMENT RESULTS IN ALTERED VASCULAR RESPONSIVENESS TO SEROTONIN AND NORADRENALINE IN ADULT RATS

V. Kristova, M. Kriska, P. Babal, D. Jezova

Department of Pharmacology and
Department of Pathology, Faculty of Medicine, Comenius University, 811 08 Bratislava, Slovakia;
Institute of Experimental Endocrinology, Slovak Academy of Sciences, 833 06 Bratislava, Slovakia

Objectives. To evaluate possible alterations of vascular responsiveness to vasoactive hormones in the vessel preparations from adult rats treated neonatally with high doses of glutamate.
Methods. The responses to noradrenaline and serotonin in perfused hindlimb vascular bed and isolated renal artery were measured in MSG-treated (2 and 4 mg/g BW) and control groups of adult rats at the age of 10 weeks. Acetylcholine test was used to assess the endothelium-dependent relaxation of the hindlimb vascular preparation. The vessel specimens from this vascular bed were evaluated histologically.
Results. Vasoconstrictory responses to noradrenaline and serotonin were significantly reduced in the hindlimb vascular bed in MSG-treated rats. In the renal artery, a significant decrease of the responses to noradrenaline was found without significant changes in the responses to serotonin. The observed changes were more pronounced in groups treated with a high dose of MSG. Comparison of relaxing responses to acetylcholine in the hindlimb preparation did not show any statistically significant differences in control and MSG treated groups. Histological evaluation of this preparations did not reveal any endothelial damage or morphological changes of vessel wall.
Conclusions. The obtained results showed reduced vascular responsiveness to vasoconstrictory agents in adult rats neonatally treated with MSG suggesting that early postnatal administration of glutamate may result in irreversible changes in cardiovascular function.

Key words: Noradrenaline - Serotonin - Glutamate (MSG) - Neurotoxic damage - Blood vessels - Vascular responsiveness - Maturation processes
Endocrine regulations, Vol. 32, 133 - 139, 1998

Download full text in PDF format (395 kB)


RADIOIMMUNOASSAY FOR AQUAPORIN-2

T. Mitsuma, J. Takagi, K. Otake, M. Kayama, Y. Mori, K. Adachi, T. Nogimori, J. Sakai, Y. Hirooka

Forth Department of Internal Medicine,
Department of Laboratory medicine and
First Department of Physiology, Aichi Medical University, Nagakute, Aichi, Aichi 480-1195, Japan and
Department of Internal Medicine, Konanshowa Hospital, Konan, Aichi, Japan

Objective. To develop radioimmunoassay for aquaporin-2 (AQP-2).
Methods. Anti-AQP-2 antiserum has been raised in New Zealand white rabbits immunized with a conjugate of synthetic AQP-2 peptide (257-271) with bovine serum albumin. Radioiodination of synthetic peptide (tyrosine-AQP2 (257-271) was performed by chloramine T method, followed by purification of radioiodinated material on Sephadex G-25 column.
Results. The obtained antibody did not crossreact with vasopressin, pituitary hormones, hypothalamic hormones and neuropeptides. The assay was performed with a double antibody system. The values are expressed as an equivalent of synthetic AQP-2 peptide (257-271). The dilution curve of high AQP-2 urine in radioimmunoassay system was parallel to the standard curve. The recovery percentage of AQP-2 added to urine was about 100 % in this assay system. Intra-assay and inter-assay variation was 4.5 % and 7.2 %, respectively. Mean urinary excretion of AQP-2 was 1.16 ng equivalent of AQP-2 (257-271)/mg creatine and was lower in patients with diabetes insipidus.
Conclusion. These data suggest that his assay system is a suitable to measure AQP-2 in urine.

Key words: Aquaporin-2 - Immunohistochemistry - Rat
Endocrine regulations, Vol. 32, 141 - 144, 1998

Download full text in PDF format (74 kB)


GONADOTROPIN RELEASING HORMONE AND SUBSTANCE P RELEASED INTO THE CEREBRAL VENTRICULAR FLUID IN INTACT, ORCHIDECTOMIZED AND SEX STEROID TREATED MALE RATS

B. Jakubowska-Naziemblo, B. Dziedzic, A. Walczewska, E. Potargowicz, W. Z. Traczyk

Department of Physiology, Institute of Physiology and Biochemistry. Medical University of Lodz, 90-131 Lodz, Poland

Objective. To evaluate whether orchidectomy (ORCX) and sex steroid hormones can modify the release of gonadotropin releasing hormone (Gn-RH) and substance P (SP) are released into the cerebral ventricular fluid (CSF).
Methods. The perfusions of lateral ventriculo-cerebello-medullary cistern were performed in anesthesised (urethane with chloralose) rats, three 30 min samples of perfusion fluid being collected in each animal. Four weeks prior to this experiment adult male rats (except INTACT group) were bilaterally orchidectomized and implanted s.c. either with empty silastic capsules (ORCX) or with these containing 17-estradiol (ORCX+E2) or testosterone propionate (ORCX+T). This procedure was performed in two series of experiments: first one for Gn-RH and second one for SP estimation by RIA. In some animals the unconjugated fraction of E2 and T was estimated in blood samples collected at the end of experiment.
Results. In all groups Gn-RH and SP were continuously released into the perfusion fluid. The mean Gn-RH concentration was higher than that of SP in the collected samples. A long-term modification of sex steroid hormone level in blood resulted in significant decrease of Gn-RH concentration only in ORCX as compared to INTACT rats, while Gn-RH and SP levels in the perfusion fluid were found relatively unchanged by a high concentration of 17-estradiol or testosterone in the peripheral circulation.

Key words: Gonadotropin releasing hormone (Gn-RH) - Substance P - Cerebrospinal Fluid - Sex steroids - Orchidectomy
Endocrine regulations, Vol. 32, 145 - 153, 1998

Download full text in PDF format (109 kB)


ACROSOMAL COMPONENT OF RAT ROUND SPERMATIDS RECOGNIZED BY A NOVEL MONOCLONAL ANTIBODY

A.I. Russinova, N.N. Atanassova, M.L. Paskaleva, L.S. Kancheva

Institute of Experimental Morphology and Anthropology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Objective. To characterize immunocytochemically the antigen recognized which appears at specific stages of germ cell development and acrosomal biogenesis by the novel monoclonal antibody (Mab 3C2).
Methods. The novel monoclonal antibody (Mab 3C2) raised against testicular Sertoli and germ cells.
Results. The immunoreactivity of this Mab in testicular sections from immature 20-day-old rats was confined to the pachytene spermatocytes. In adult testis the Mab 3C2, besides meiotic cells, recognized also acrosomal component of round spermatids. The immune reaction was observed in Golgi and cap phases of acrosomal development until the stage VIII of the cycle of the seminiferous epithelium. Immunostaining was absent in acrosome of elongating and mature spermatids and indicated that some modifications in acrosomal protein may exist in subsequent stages of acrosomal development.
Conclusions. Novel Mab 3C2 shares a common antigen in pachytene spermatocytes and round spermatids. Therefore, it may be a marker of meiotic and postmeiotic germ cells.

Key words: Immunocytochemistry - Novel monoclonal antibody - Spermatogenesis - Acrosome - Spermatocytes - Round Spermatids
Endocrine regulations, Vol. 32, 155 - 159, 1998

Download full text in PDF format (422 kB)


REPEATED MATERNAL DEPRIVATION ALTERS BEHAVIORAL PATTERN AND ATTENUATES PROLACTIN RESPONSE TO MILD STRESSOR IN ADULT MALE WISTAR RATS

J. Jurcovicova, M. Dobrakovova, S. Zorad

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

Objective. To evaluate the impact of repeated neonatal mother deprivation (RMD) of male rats on the behavioral parameters and response of prolactin to mild stress stimuli in the adulthood.
Methods. Afer birth, the pups of Wistar Porton Olac rats were crossfostered and their number was adjusted to 8 per litter (4 males and 4 females). They were removed from the dam for 6 hours daily on postnatal day 6, 7, 8 and for 12 hours daily on postnatal day 12, 13, 15, 16 and placed to another cage lined with cotton wool at controlled temperature 37C. Body weight was estimated repeatedly from postnatal day 9 to 97. At 14 weeks of life the behavioral activity was measured in an open field on 2 occasions, 2 days apart. One week later the rats were exposed to 15 min novelty stress or to 3 min handling and decapitated 15 min after the initiation of both. Trunk blood was collected and plasma prolactin (PRL) was measured by radioimmunoassay.
Results. On postnatal day 15 the eye opening was found in 75% of control pups and 73 % of pups with RMD. In the rats after RMD the body weight gain was significantly decreased from day 21 until the day 97. Vertical behavioral activity (rearing) was enhanced in RMD rats when measured on the first occasion. Horizontal behavioral activity did not significantly differ from the control group. Stress of novel environment elicited the activation of PRL secretion in untreated animals (19.3 14.6 ng/ml vs. 7.171.03 ng/ml, P<0.05), while no change was found in the rats after RMD (8.152.0 ng/ml vs. 4.350.48 ng/ml).
Conclusions. In the rats exposed to neonatal mother deprivation the lower emotionality was found. Significantly decreased body weight gain in these animals was probably due to the nutritional deprivation during the postnatal separation from the mother. The nonresponsiveness of lactotrophs to mild stressor in adult rats after RMD may have a negative impact on defense mechanisms to immune challenges.

Key words: Rats - Neonatal mother deprivation - Open field - Stress - Prolactin
Endocrine regulations, Vol. 32, 161 - 165, 1998

Download full text in PDF format (83 kB)