Maria Fickova

Effects of selected endocrine disruptors on meiotic maturation, cumulus expansion, synthesis of hyaluronan and progesterone by porcine oocyte-cumulus complexes.

In most mammals, before ovulation, cumulus cells synthesize a large amount of hyaluronan (HA) that is organized into an extracellular matrix (ECM), which provides an essential microenvironment for in vivo oocyte fertilization. This process is called cumulus expansion. The present study assessed effects of selected endocrine disruptors (bisphenol A, BPA; 4-chloro-3-methyl phenol, CMP; di(2-ethylhexyl) phthalate, DEHP; and benzyl butyl phthalate, BBP) in a range of 100pM-100microM, on follicle-stimulating hormone (FSH)-induced meiotic maturation and cumulus expansion of porcine oocyte-cumulus complexes (OCC) cultured in vitro. Moreover, FSH-stimulated production of hyaluronic acid (HA) and progesterone by cumulus cells was measured. Both phenols, BPA and CMP (100microM), significantly affected meiotic maturation of oocytes. The number of oocytes that underwent germinal vesicle breakdown (GVBD) (78.7% and 72.4%, respectively) as well as the rate of oocytes that reached metaphase II stage (MII) (50% and 53.6%, respectively) after 44h culture were decreased compared to control (89.6% for GVBD and 81.5% for MII). FSH-stimulated expansion of cumulus was altered by the highest concentration of BPA and CMP (70% and 64%, respectively vs. 80.3% in control). Although BPA did not alter FSH-stimulated HA synthesis by cumulus cells, its incorporation within the complex was reduced to a half of control value. Progesterone production by OCC was significantly changed in the presence of BPA or DEHP. Finally, our results provide valuable information that oocyte meiotic progression was adversely affected during in vitro culture with endocrine disruptors.

A comparison of the effects of tributyltin chloride and triphenyltin chloride on cell proliferation, proapoptotic p53, Bax, and antiapoptotic Bcl-2 protein levels in human breast cancer MCF-7 cell line

In recent years it was disclosed, that numerous organotin(IV) derivatives have remarkable cytotoxicity against several types of cancer cells. The property to inhibit cell growth makes these compounds promising for antitumor therapy, as the clinical effectiveness of cisplatin is limited by drug resistance and significant side effects. Tributyltin and triphenyltin are known as endocrine disruptors. Moreover, the compounds exert their toxicity in mammals predominantly through nuclear receptor signaling. Here we present the effects of tributyltin chloride (TBT-Cl) and triphenyltin chloride (TPT-Cl) on cell proliferation, expression of proapoptotic p53, Bax, and antiapoptotic Bcl-2 proteins in human breast cancer MCF-7 cell line. Dose and time dependent (24, 48 and 72 h) cell expositions have demonstrated TBT-Cl as more effective in inhibiting MCF-7 cell proliferation than TPT-Cl. Short time treatment with TBT-Cl displayed marked stimulation of p53 protein expression when compared to TPT-Cl. Both organotin compounds displayed similar mild enhancement of Bax protein expression. The 24h exposition of TPT-Cl induced substantial diminution of Bcl-2 protein expression in comparison with both, untreated cells and TBT-Cl treated cells. Our observations indicate that TBT-Cl and TPT-Cl have different antiproliferative potency and distinct impact on expression of apoptosis marker proteins.

Metabolic changes in the animals subjected to space flight

The activity of the enzymes involved in aminoacid metabolism (tyrosine aminotransferase, TAT, tryptophan pyrrolase TP, serine dehydratase, SD) with rapid response to glucocorticoids and enzymes requiring for activity increase repeated administration of corticosterone (alanine aminotransferase, ALT, aspartate aminotransferase, AST) in liver, the changes of lipolysis in adipose tissue and the plasma corticosterone levels were studied in rats subjected to space flight (F), in animals from synchron model experiments (SM, simulated conditions of space flight in laboratory) and in intact controls (C). The increase of plasma corticosterone concentration and of the activity of rapidly (TAT, TP, SD) and slowly activating enzymes (ALT, AST) was found in F group 6-10 hr after space flight (18.5 days on biosatellite COSMOS 1129). This suggested the presence of acute-stress (associated primarily with the landing) and chronic stress induced hypercorticosteronemia during the flight. After the short 6-day period of recovery the plasma corticosterone concentrations and the activities of liver enzymes returned to control levels. The exposition of animals to repeated immobilization stress showed higher response of corticosterone levels in flight rats as compared to intact controls. No changes in basal lipolysis were observed in flight rats in comparison to intact controls, however the stimulation of lipolysis by norepinephrine was lower in animals from F and SM groups. This lower response of lipolytic processes to norepinephrine was found in flight animals also after six days period of recovery. These results showed that there are important changes in the regulation of lipolytic processes in adipose tissue of rats after space flight and in the conditions of model experiments.

Insulin and Catecholamines Act at Different Stages of Rat Liver Regenerationa

Insulin and catecholamines are known to exert effects on hepatocyte growth and metabolism. The binding of insulin, the plasma levels of insulin (INS), and the plasma catecholamine levels of epinephrine (EPI) and norepinephrine (NE) were measured during liver regeneration after partial hepatectomy (PH). A significant decrease (p < 0.05) of INS receptor binding capacity was found at 1, 2, and 3 days after operation. A single insulin injection (2.5 IU/kg body weight) at 24 h after sham operation or partial hepatectomy did not affect these changes of INS binding to hepatocytes. The plasma insulin and glucose levels were similar in both hepatectomized and sham-operated rats. Within 20 min after liver resection or sham operation, plasma NE and EPI concentrations increased rapidly. Then, a significant decrease was observed in plasma catecholamine levels at 1 h after laparotomy and PH. In both groups, laparotomized and partially hepatectomized plasma levels of NE at 4 h reached control values and remained unchanged at the 4- and 24-h periods. After PH, the levels of EPI remained elevated at 4 h in comparison with laparotomy. Adrenal tyrosine hydroxylase mRNA levels were significantly elevated at 4 h in both PH and sham-operated groups. These results suggest that signals that are initiated by catecholamines and transduced through second messengers presumably participate in the trigger mechanism of liver regeneration, while insulin (considered as a secondary mitogen) enhances a stimulus for liver regeneration.

Terguride Treatment Attenuated Prolactin Release and Enhanced Insulin Receptor Affinity and GLUT 4 Content in Obese Spontaneously Hypertensive Female, but Not Male Rats

Abstract: Glucose tolerance, serum insulin, insulin receptors in epididymal fat tissue, and GLUT 4 content in muscle, as well as serum prolactin, were studied in obese and lean spontaneously hypertensive rats (SHRs) of both sexes. Obese animals displayed insulin resistance and decreased capacity of high‐affinity binding sites of insulin receptors in fat tissue plasma membranes. GLUT 4 content in musculus quadriceps was diminished only in obese females. Terguride treatment lowered prolactin serum levels, which was concomitant with ameliorated insulin sensitivity in obese animals of both sexes. Similarly, only in obese females, terguride significantly increased the affinity of high‐affinity insulin‐binding sites and normalized GLUT 4 content. Our results document downregulation of insulin receptors and GLUT 4 in obesity and suggest a role for prolactin in obesity‐induced insulin resistance, particularly in female rats.

Modulation of cAMP level by tedisamil in guinea pig heart

Tedisamil is antiarrhythmic class III drug with antifibrillating/defibrillating potency linked to enhancement of intermyocyte gap junctional electrical coupling most likely via its sympathomimetic cAMP-related mechanisms. This study was designed to examin the effect of tedisamil on cAMP level in guinea pig hearts in vivo and in vitro in Langendorff preparation. The drug was administered either as a bolus into vena jugularis in dosage 1.0 and 1.5 mg/kg or into the perfusion solution at a concentration of 1.5 × 10-6 mol/l. In additional experiments, this period was followed by brief 10 min global ischemia, induced by clamping of the aorta or perfusion. After 10 min from the onset of tedisamil administration as well as after 10 min of ischemia the ventricular tissue was immediately frozen for cAMP immunoassay Tedisamil caused in normal heart small but significant dose-dependent increase of myocardial cAMP (pmol/mg) level in vivo 1.8 and 2.5 vs. 1.4 as well as in vitro 1.1 vs. 0.8 (p < 0.05) conditions. Ischemia itself induced accumulation of cAMP in both, in vitro and in vitro experiments, 2.6 vs. 1.4 and 1.3 vs. 0.8, respectively. The preischemic elevation of cAMP by tedisamil was not potentiated by following ischemia, on the contrary, decline of the cyclic nucleotide was detected comparing to ischemia itself. In conclusion, tedisamil increased cAMP level in normal heart and prevented additional ischemia-related elevation of this nucleotide. The results indicate modulation of myocardial cAMP level by tedisamil, which may account for its protective effect on gap junctional electrical coupling.

Effect of dietary fish oil on 2-deoxy-D-3H glucose uptake in isolated adipocytes of rats fed various diets.

High sucrose diet-induced insulin resistance and mild glucose intolerance are associated with decreased insulin binding to isolated adipocytes and reduced insulin action in adipose tissue. Enhanced dietary intake of omega-3 polyunsaturated fatty acids (n-3-FA) counteracts these disorders. To provide more information on the possible role of membrane-related glucose transport processes, basal and insulin-stimulated 2-deoxy-D-3H glucose uptake was evaluated in isolated adipocytes obtained from rats on various dietary regimens. For 2 weeks animals were fed three different isocaloric (18 cal% proteins, 19 cal% fat, and 63 cal% carbohydrate) diets: (1) a standard rat chow (B), (2) a high sucrose diet (S, 63 cal% sucrose), or (3) an S diet supplemented with marine fish oil (S + FO, Martens, 30 wt% of n-3-FA). High dietary n-3-FA intake resulted in a significant decline in both basal (0.05 +/- 0.01 pmol/10(6) fat cells; mean +/- SEM) and insulin-stimulated (10(-6) M) (0.20 +/- 0.01) glucose uptake when compared with the control (basal: 0.12 +/- 0.02; insulin: 0.35 +/- 0.02) and/or the S group (basal: 0.18 +/- 0.03; insulin: 0.43 +/- 0.03), indicating decreases in insulin responsiveness and sensitivity (ED50: B: 0.03 +/- 0.01; S: 0.03 +/- 0.01; S + FO: 0.73 +/- 0.2 nM; p < 0.01 for S + FO vs B and S + FO vs S). Fish oil supplementation induced an increase in adipocyte size (B: 69 +/- 1.6; S: 70 +/- 2.5 and S + FO: 76 +/- 2.2 microns; B: S + FO p < 0.05) and a decrease in plasma membrane microviscosity (B: 4.08 +/- 0.3; S: 5.39 +/- 0.5; S + FO: 3.10 +/- 0.3; p < 0.05). Rates of basal and insulin-stimulated glucose uptake did not correlate with plasma membrane microviscosity; however, a negative relation to fat cell size was found (r = -0.484; p < 0.05). On the other hand, a positive correlation between both basal (r = 0.504; p < 0.05) and insulin-stimulated (10(-6) M, r = 0.640; p < 0.02) glucose uptake and blood glucose levels was observed. In conclusion, these data (a) suggest a less important role of diet-induced changes in plasma membrane microviscosity for glucose uptake in adipose tissue, and (b) leave unclear the mechanism of why dietary fish oil decreases the sensitivity of glucose uptake to insulin in isolated rat adipocytes.

Changes of hormones regulating electrolyte metabolism after space flight and hypokinesia

The changes of hormones in plasma involved in the body fluid regulation were studied in human subjects during and after space flights in relation to redistribution of body fluids in the state of weightlessness. Since hypokinesia was used as a model for simulation of some effects of the stay in microgravity the plasma hormone levels in rats exposed to hypokinesia were also investigated. Plasma aldosterone values showed great individual variations during the first inflight days, the increased levels were observed with prolongation of space flights. The important elevation was found in the recovery period, however it was interesting to note, that in some cosmonauts with repeated exposure to space flight, the postflight plasma aldosterone levels were not elevated. The urine excretion of aldosterone was increased inflight, however in postflight period the decrease or increase were found in the first 1-5 days. The increase of plasma renin activity was observed in flight and postflight period. The rats were exposed to hypokinesia (forced restriction of motor activity) for 1, 7 and 60 days and urine was collected during last 24 hours. The animals were sacrificed and the concentration of electrolytes and of levels of corticosterone, aldosterone (A), ANF and plasma-renin activity (PRA) were determined in plasma. In urine excretion of sodium and potassium were estimated. An important increase of plasma renin activity and aldosterone concentration was found after short-term hypokinesia (1 day). These hormonal values appear to decrease with time (7 days) and are not significantly different from controls after long-term hypokinesia (60 days). A decrease of values ANF in plasma was observed after 1 and 7 days hypokinesia. After prolonged hypokinesia a decrease of sodium plasma concentration was observed. The excretion of sodium in urine was higher in long-term hypokinetic animals. There were no significant changes of plasma potassium levels in rats exposed to hypokinesia, however the urinary excretion of potassium was elevated. In rats exposed to hypokinesia for 7 and 60 days an increase of urine osmolality was observed. The results of hormone and electrolyte determination in plasma of cosmonauts after space flight and in experimental animals after hypokinesia suggested that in evaluation of relations between the changes of hormone levels and electrolyte in plasma and urine other factors like emotional stress working load; altered diurnal cycles should be considered in interpretation of homeostatic response of fluid and electrolyte metabolism to space flight conditions.

Changes of insulin effect on lipogenesis and insulin binding receptors during hypokinesia.

The effect of hypokinesia on insulin action and insulin binding to specific receptors in fat cells was studied. Male Wistar rats were exposed to hypokinesia in special adjustable plastic cages for 1, 7, 21 and 60 days, and the stimulatory effect of insulin (10 and 100 mU) on the incorporation of radiocarbon labelled glucose into lipids of fat tissue and the binding of insulin to receptors of isolated adipocytes was estimated. The stimulation of lipogenesis by insulin was slightly diminished after hypokinesia for 1 day, however, an important increase of insulin action was found in rats exposed to hypokinesia for 60 days. The decrease of insulin binding capacity of the number of binding sites per cell and of the insulin receptor density was found after 1 day of hypokinesia. In rats exposed to hypokinesia for 60 days, in agreement with the higher stimulatory affect of insulin, an increase of insulin receptor density was observed. These results showed that hypokinesia has an important influence on stimulatory action of insulin and on insulin receptors in adipocytes.

The effect of hypokinesia on lipid metabolism in adipose tissue.

The increase of nonesterified fatty acid (NEFA) concentration in plasma was observed in rats subjected to hypokinesia for 1-60 days. In the period of recovery (7 and 21 days after 60 days immobilization) the content of NEFA returned to control values. The increase of fatty acid release from adipose tissue was observed in hypokinetic rats, however the stimulation of lipolysis by norepinephrine was lower in rats exposed to hypokinesis. The decrease of the binding capacity and a diminished number of beta-adrenergic receptors were found in animals after hypokinesia. The augmentation of the incorporation of glucose into lipids and the marked increase in the stimulation of lipogenesis by insulin were found in adipose tissue of rats subjected to long-term hypokinesia. These results showed an important effect of hypokinesia on lipid mobilization, on lipogenesis and on the processes of hormone regulation in adipose tissue.