DHEA lessens depressive-like behavior via GABA-ergic modulation of the mesolimbic system

Alterations in the levels of dehydroepiandrosterone (DHEA) in the brain can allosterically modulate gamma-aminobutyric-acid-type-A (GABA(A)R), N-methyl-D-aspartate (NMDAR), and Sigma-1 (sigma 1R) receptors. In humans, DHEA has antidepressive effects; however, the mechanism is unknown. We examined whether alterations in DHEA also occur in an animal model of depression, the Flinders-sensitive-line (FSL) rats, with the intention of determining the brain site of DHEA action and its antidepressant mechanism. We discovered that DHEA levels were lower in some brain regions involved with depression of FSL rats compared to Sprague-Dawley (SD) controls. Moreover, DHEA (1 mg/kg IP for 14 days)-treated FSL rats were more mobile in the forced swim test than FSL controls. In the NAc and VTA, significant changes were observed in the levels of the delta-subunit of GABA(A), but not of sigma 1R mRNA, in FSL rats compared to SD rats. The delta-subunit controls the sensitivity of the GABA(A)R to the neurosteroid. Indeed, treatment (14 days) of FSL rats with the GABA(A) agonist muscimol (0.5 mg/kg), together with DHEA (a negative modulator of GABA(A)), reversed the effect of DHEA on immobility in the swim test. Perfusion of DHEA sulfate (DHEAS) (3 nM and 30 nM for 14 days) into the VTA and NAc of FSL rats improved their performance in the swim test for at least 3 weeks post-treatment. Our results imply that alterations in DHEA are involved in the pathophysiology of depression and that the antidepressant action of DHEA is mediated via GABA(A)Rs in the NAc and VTA.

Dynamic genetic architecture of metabolic syndrome attributes in the rat

The polydactylous rat strain (PD/Cub) is a highly inbred (F > 90) genetic model of metabolic syndrome. The aim of this study was to analyze the genetic architecture of the metabolic derangements found in the PD/Cub strain and to assess its dynamics in time and in response to diet and medication. We derived a PD/Cub × BN/Cub (Brown Norway) F2 intercross population of 149 male rats and performed metabolic profiling and genotyping and multiple levels of genetic linkage and statistical analyses at five different stages of ontogenesis and after high-sucrose diet feeding and dexamethasone administration challenges. The interval mapping analysis of 83 metabolic and morphometric traits revealed over 50 regions genomewide with significant or suggestive linkage to one or more of the traits in the segregating PD/Cub × BN/Cub population. The multiple interval mapping showed that, in addition to “single” quantitative train loci, there are more than 30 pairs of loci across the whole genome significantly influencing the variation of particular traits in an epistatic fashion. This study represents the first whole genome analysis of metabolic syndrome in the PD/Cub model and reveals several new loci previously not connected to the genetics of insulin resistance and dyslipidemia. In addition, it attempts to present the concept of “dynamic genetic architecture” of metabolic syndrome attributes, evidenced by shifts in the genetic determination of syndrome features during ontogenesis and during adaptation to the dietary and pharmacological influences.

Distribution of two splice variants of the glutamate transporter GLT-1 in the developing rat retina

The distributions of a carboxyl terminal splice variant of the glutamate transporter GLT-1, referred to as GLT-1B, and the carboxyl terminus of the originally described variant of GLT-1, referred to hereafter as GLT-1 alpha, were examined using specific antisera. GLT-1B was present in the retina at very early developmental stages. Labelling was demonstrable at embryonic day 14, and strong labelling was evident by embryonic day 18. Such labelling was initially restricted to populations of cone photoreceptors, the processes of which extended through the entire thickness of the retina and appeared to make contact with the retinal ganglion cells. During postnatal development the GLT-1B-positive photoreceptor processes retracted to form the outer plexiform layer, and around postnatal day 7, GLT-1B-immunoreactive bipolar cells appeared. The pattern of labelling of bipolar cell processes within the inner plexiform layer changed during postnatal development. Two strata of strongly immunoreactive terminals were initially evident in the inner plexiform layer, but by adulthood these two bands were no longer evident and labelling was restricted to the somata and processes (but not synaptic terminals) of the bipolar cells, as well as the somata, processes, and terminals of cone photoreceptors. By contrast, GLT-1 alpha appeared late in postnatal development and was restricted mainly to a population of amacrine cells, although transient labelling was also associated with punctate elements in the outer plexiform layer, which may represent photoreceptor terminals.

Metabolic characteristics and body composition in a model of anti-obese rats (Lou/C)

OBJECTIVE

The aims of this study were to investigate some features of the metabolic profile and the body composition of male Lou/C rats and to examine whether these characteristics are strictly related to the food-intake reduction.

RESEARCH METHODS AND PROCEDURES

Fourteen-week-old male Lou/C rats were compared with age-matched male Wistar rats fed ad libitum (WAL) and another group of male Wistar rats whose food was chronically restricted (WFR) to the same amount as the Lou/C rats from weeks 3 to 14.

RESULTS

Food intake and body weight were significantly (p < 0.01) reduced in Lou/C compared with WAL rats, whereas these reductions were perfectly reproduced in WFR rats. Lou/C rats demonstrated lower relative weights of retroperitoneal (0.97 +/- 0.07 vs. 1.67 +/- 0.16 and 1.88 +/- 0.15 g/100 g body) and epididymal (1.01 +/- 0.02 vs. 1.62 +/- 0.12 and 1.80 +/- 0.11 g/100g body) fat depots than did the two other groups and no decrease in the percentage of carcass proteins, which was observed in the WFR rats. In addition, compared with the WFR group, the Lou/C rats showed lower plasma glucose levels (3.65 +/- 0.14 vs. 4.72 +/- 0.15 and 4.7 +/- 0.19 mM); a tendency (p < 0.1) for lower liver glycogen concentrations; and similar levels of glycerol, free fatty acids, and beta-hydroxybutyrate concentrations. Epinephrine and the relative weight of the adrenal glands were significantly (p < 0.01) lower in the Lou/C rats than in the WAL rats and the two other groups, respectively.

DISCUSSION

The ability of the Lou/C rats to accumulate less body fat than their equally food-restricted Wistar counterparts (WFR) suggests a difference in basal metabolism in this strain of rats that resembles obesity-resistant rats.

The newly inbred cohen diabetic rat: a nonobese normolipidemic genetic model of diet-induced type 2 diabetes expressing sex differences

The newly inbred Cohen diabetic rat is an exceptional experimental model of diet-induced type 2 diabetes mellitus that is the result of secondary inbreeding nearly 30 years after it originally had been established. Animals from the original colony were selectively inbred by stringent criteria for 10 additional generations, bringing overall inbreeding to >50 generations. The metabolic phenotypes of the resulting contrasting strains, designated as the Cohen diabetic-sensitive (CDs) and -resistant (CDr) rats, were characterized. The phenotype of the CDs strain that was fed a regular diet consisted of fasting normoglycemia, normal glucose tolerance to intraperitoneal glucose loading, normal fasting insulin levels, and a normal insulin response to glucose loading. In contrast, CDs rats that were fed a custom-prepared high-sucrose low-copper diabetogenic diet became overtly diabetic: fasting glucose levels were normal or elevated, and the blood glucose insulin response to glucose loading was markedly abnormal. CDr rats that were fed a regular or diabetogenic diet did not develop diabetes and maintained normal glucose tolerance and insulin secretion. A striking sex difference was observed in CDs rats that were fed a diabetogenic diet: males had a lower growth rate and a more severe glucose intolerance pattern than females. Gonadectomy shortly after weaning did not prevent the development of the diabetic phenotype in its early phase in either sex but markedly attenuated its expression in males at a later phase, abolishing the sex differences. Alternate-day feeding, as opposed to daily feeding, also attenuated the metabolic phenotype in males. The development of the diabetic phenotype in CDs rats that were fed a diabetogenic diet was not accompanied by obesity or hyperlipidemia. The genetic profile of the strains was established using 550 microsatellite markers evenly distributed throughout the rat genome. The rate of homozygosity within strain was > or = 96%. The rate of polymorphism between the contrasting strains was 43%. We conclude that the metabolic phenotypes of the rebred colony of CDs and CDr rats and their genetic makeup render the Cohen diabetic rat a useful experimental model that is highly suitable for studying the interaction between nutritional-metabolic environmental factors and genetic susceptibility (sensitivity and resistance) for the development of type 2 diabetes. The model is also distinctively useful for investigating the effect of sex on the expression of the diabetic phenotype.

Common properties for propargylamines of enhancing superoxide dismutase and catalase activities in the dopaminergic system in the rat: implications for the life prolonging effect of (-)deprenyl

(-)Deprenyl has been reported to prolong the life span of different animal species. Further, the drug effectively increases antioxidant enzyme activities such as superoxide dismutase (SOD) and catalase (CAT) in brain dopaminergic regions. We have found that the effect of the drug on antioxidant enzyme activities is highly dose dependent, increasing with an increasing dose, however, a higher dose becomes less effective and an excessive dose becomes adversely effective. Most importantly, an optimal dose for the effect varies widely depending on animal species, strain, sex, age and duration of the treatment, which may at least partly explain discrepancies reported among different studies in the past. From the parallelism of the dose-effect relationship of the drug between life span extension and increasing endogenous antioxidant enzyme activity, we have suggested that the above two effects of (-)deprenyl may be causally related. This review summarizes our past series of studies and also reports our very recent observation that other propargylamines such as rasagiline and (R)-N-(2-heptyl)-N-methylpropagylamine (R-2HMP) also share the property of enhancing antioxidant enzyme activities. Further, our most recent study has found that these propargylamines increase antioxidant enzyme activities not only in brain dopaminergic regions but in extra-brain dopaminergic tissues such as the heart and kidneys. These observations are discussed in relation to the life prolonging effect of (-)deprenyl reported in the past.

Liver and kidney kynurenine aminotransferase activity in different strains of rats

Variations in liver and kidney kynurenine aminotransferase (KAT) activity in Pittsburg-Yoshida, Brown-Norway, albino Wistar, Sprague-Dawley, Long Evans and heterozygous Gunn rats were studied. In liver, values of KAT specific activity, expressed as mumoles of kynurenic acid formed per hour per mg of protein, were different in the groups of Brown-Norway and Pittsburg-Yoshida rats versus Long Evans and Sprague-Dawley rats. The activity expressed as mumoles of kynurenic acid per g of fresh liver showed other differences, being significantly higher in Gunn with respect to other strains of rats and lower in Pittsburg-Yoshida and Brown-Norway rats. In addition, KAT activity was significantly lower in Pittsburg-Yoshida than in Brown-Norway rats. In kidney, the specific activity of kynurenine aminotransferase showed significant differences in the values of Sprague-Dawley and Long Evans rats versus the other strains. The activity expressed per g of fresh tissue was significantly higher in Wistar, Sprague-Dawley, Long Evans and Gunn than in Pittsburg-Yoshida and Brown-Norway rats. No significant differences were found in values between hyperlipidemic Pittsburg-Yoshida and their control Brown-Norway rats. These results high-light the importance of considering various rat strains when inbred animal experimental models are used.

Effects of chronic alcohol consumption on the expression of different NR1 splice variants in the brain of AA and ANA lines of rats

Following chronic alcohol treatment alterations in N-methyl-D-aspartate receptor subunit 1 and 2 (NR1 and NR2), mRNA and protein levels have been reported. The NR1 gene undergoes alternative RNA splicing, resulting in eight splice variants, which were shown to differ in their sensitivity to alcohol. Here, we studied mRNA and protein levels of NR1 splice variants in alcohol-preferring (AA) and alcohol-nonpreferring (ANA) rat lines under basal conditions (alcohol-naive), and following chronic alcohol consumption. mRNA levels of three NR1 splice variants (NR1-1, NR1-2, NR1-4), and the protein levels of NR1 (NR1-1/NR1-2), and of NR1 alternative C-terminus (NR1-3/NR1-4) were determined in the hippocampus and nucleus accumbens by competitive RT-PCR and Western blot analysis, respectively. No significant differences in NR1 mRNA, or protein levels were found in the nucleus accumbens between the two rat lines under basal conditions, or following chronic alcohol consumption. In the hippocampus of alcohol-naive rats, the NR1-4 mRNA content was significantly higher in ANA compared to AA rats, however, no significant difference could be detected at the protein level. Following chronic alcohol consumption, the protein level of the NR1 alternative C-terminus (NR1-3/NR1-4) was significantly higher in AA rats compared to the corresponding control. Taken together, these results suggest: (i) brain site-specific alterations in NMDA receptor subunit composition occur following chronic alcohol consumption. (ii) In the hippocampus, NR1 splice variant mRNA levels differ between AA and ANA rats. (iii) The mRNA levels and protein levels of NR1 splice variants are differentially affected by chronic alcohol consumption.

Photoreceptor cell damage by light in young Royal College of Surgeons rats

PURPOSE

To determine the effects of genetic background and light rearing conditions on intense-light-mediated retinal degeneration in young RCS rats.

MATERIALS AND METHODS

Albino rats, homozygous or heterozygous for the rdy gene were bred and born in dim cyclic light. At P7 they were moved to a dark environment, and maintained there until exposure to intense visible (green) light at P18 or P25. Other rats remained in the dim cyclic light environment. At various times between P11 and P40 rats were killed for determinations of rhodopsin and photoreceptor cell DNA levels, western transblot analysis of retinal S-antigen (arrestin) and alpha-transducin, or northern slot blot analysis of their respective mRNA levels.

RESULTS

At P18, unexposed dark maintained homozygous RCS rats and their phenotypically normal heterozygous counterparts have nearly equivalent rhodopsin levels and photoreceptor cell DNA. Intense light exposure at this age, to 8 hours of continuous light or 3 hours of intermittent light, did not lead to a loss of either rhodopsin or retinal DNA when compared with their respective unexposed controls. At P25 rhodopsin levels were higher than at P18, while photoreceptor cell DNA was essentially the same as in the younger rats. However, intense light exposure at P25 resulted in substantial losses of rhodopsin and photorecptor cell DNA and the losses were greater in homozygous rats than in heterozygous animals. Light damage of P25 rats maintained in dim cyclic light was essentially the same as in dark maintained homozygous rats, but no damage was found in the heterozygous animals. By western analysis, alpha-transducin levels in the retina increased with time in darkness, while retinal S-antigen levels either remained the same or decreased during the period P15-P35. For rats in the cyclic light environment S-antigen expression was greater than alpha-transducin at all ages. Slot blot analysis of mRNAs for the two proteins generally followed the patterns seen by western analysis. S-antigen mRNA was expressed at an earlier age and at higher levels than alpha-transducin in both types of rats from both light rearing conditions. Peak expression of S-antigen most often occurred at P18 in both the heterozygous and homozygous rats.

CONCLUSIONS

The relative expressions of S-antigen and alpha-transducin in P18 and P25 rats correlates with their relative resistance to retinal light damage at P18 and their enhanced susceptibility at P25. Rats homozygous for the rdy gene also exhibit more damage than heterozygous animals when photoreceptor cell DNA is used to estimate the extent of retinal light damage.

Effects of testosterone and progesterone on brain 5alpha-reductase and aromatase in Long-Evans males and comparison of aromatase in Long-Evans vs. Sprague-Dawley rats

We investigated medial basal hypothalamic-preoptic area (MBH-POA) 5alpha-reductase and aromatase enzyme activities in gonadally intact and castrated adult Long-Evans (L-E) male rats treated with testosterone (T), progesterone (P), and a combination of T+P. MBH-POA 5alpha-reductase and aromatase activities did not differ significantly among the groups. The lack of a difference in MBH-POA aromatase between control and castrated L-E animals was unexpected. In two further experiments, MBH-POA aromatase was examined in intact and castrated L-E and Sprague-Dawley (S-D) rats, using direct and indirect assays. The activity in castrated S-D (but again, not in L-E) rats significantly decreased compared to control values. These data suggest that the absence of gonads does not decrease MBH-POA aromatase in adult L-E rats.

Genetic profiles of newly inbred Dahl/Iwai salt-sensitive and salt-resistant rats

Dahl-Iwai salt-sensitive (S) and salt-resistant (R) rat strains were established as inbred strains at Brookhaven National Laboratory, NY, and were introduced into Eisai Co., Ltd., Japan, and designated DIS/Eis and DIR/Eis. To examine whether there are different allele distributions among the substrains of inbred Dahl S and R rats, we determined biochemical and immunological alleles of DIS/Eis and DIR/Eis, and SS/Sea and SR/Sea, which were derived from SS/Jr and SR/Jr, which were developed by Rapp and Dene. Several differences of allele distribution were observed, indicating that the substrains have different genetic backgrounds. The phenotypic differences between the substrains, such as the severity of the hypertension induced, could be ascribed to the different genetic backgrounds.

Hepatic microsomal enzyme induction, beta-oxidation, and cell proliferation following administration of clofibrate, gemfibrozil, or bezafibrate in the CD rat

Male and female CD rats were administered one of two dose levels of clofibrate, gemfibrozil, or bezafibrate daily by oral gavage for a period of 14 days in order to establish an empirical data base using the Charles River CD rat with a single class of drugs against which the potency of novel proprietary compounds could be compared. Subsequent gross examination of the liver indicated significant and dose-related increases in relative and absolute liver weights in males following clofibrate and gemfibrozil. In females, absolute and relative liver weights were significantly elevated to a similar degree with either dose of gemfibrozil, and absolute liver weights were higher in clofibrate-dosed animals. Bezafibrate had no effect on female liver weights. Clofibrate and gemfibrozil increased hepatic palmitoyl CoA beta-oxidation in both sexes; however, clofibrate had the greater effect in males and gemfibrozil had the least effect in females. Bezafibrate treatment resulted in a very pronounced elevation of palmitoyl CoA beta-oxidation in the males but had no similar effect in the females. Concurrent ELISA analysis for cytochrome CYP4A revealed very good correspondence between beta-oxidation and cytochrome induction for each of the three compounds in males, but other cytochromes were not greatly affected, except CYP1A1 which was elevated in bezafibrate-dosed females. For males, further analysis for markers of cellular proliferation, namely cyclin-dependent kinases (CDK) and proliferating cell nuclear antigen (PCNA), indicated dose-related increases for both with clofibrate, increases at the high dose for gemfibrozil, and, for PCNA, a dose-related increase for bezafibrate. In females, both markers for cell proliferation showed either slight or no increases following any of the three drug treatments. These results demonstrate clear sex-dependent differences in terms of relative potency in the hepatic response of the Sprague-Dawley-derived rat to these peroxisome proliferators. Bezafibrate is most potent and gemfibrozil is least potent in stimulating peroxisome-associated beta-oxidation and cytochrome P450 4A induction in the males. Even though gemfibrozil significantly increased liver weights, beta-oxidation and cytochrome P450 4A in the females increased only after clofibrate treatment, although to a lesser degree than in the males administered the same dose. Similar sex-related differences were observed for cell proliferation. In conclusion, sex-related differences were noted in the potency to stimulate acyl Co-A oxidation, its association with hepatomegaly, and the stimulation of cell proliferation, but CYP4A induction always accompanied any substantial drug-dependent increases in beta-oxidation.

Ventilation and metabolism among rat strains

We examined ventilation and metabolism in four rat strains with variation in traits for body weight and/or blood pressure regulation. Sprague-Dawley [SD; 8 males (M), 8 females (F)], Brown Norway (BN; 10 M, 11 F), and Zucker (Z; 11 M, 12 F) rats were compared with Koletsky (K; 11 M, 11 F) rats. With the use of noninvasive plethysmography, frequency, tidal volume, minute ventilation (VE), O2 consumption, and CO2 production were derived at rest during normoxia (room air) and during the 5th minute of exposure to each of the following: hyperoxia (100% O2), hypoxia (10% O2-balance N2), and hypercapnia (7% CO2-balance O2). Statistical methods probed for strain and sex effects, with covariant analysis by body weight, length, and body mass. During resting breathing, strain effects were found with respect to both frequency (BN, Z > K, SD) and tidal volume (SD > BN, Z) but not to VE. Sex influenced frequency (F > M) alone. Z rats had higher values for O2 consumption, CO2 production, and respiratory quotient than the other three strains, with no independent effect by sex. During hyperoxia, frequency was greater in BN and Z than in SD or K rats; SD rats had a larger tidal volume than BN or Z rats; Z rats had a greater VE than K rats; and M had a larger tidal volume than F. Strain differences persisted during hypercapnia, with Z rats exhibiting the highest frequency and VE values. During hypoxic exposure, strain effects were found to influence VE (SD > K, Z), frequency (BN > K), and tidal volume (SD > BN, K, Z). Body mass was only a modest predictor of VE during normoxia, of both VE and tidal volume with hypoxia, hypercapnia, or hyperoxia, and of frequency during hypercapnia. We conclude that strain of rats, more than their body mass or sex, has major and different influences on metabolism, the pattern and level of ventilation during air breathing, and ventilation during acute exposure to hypercapnia or hypoxia.

Pyruvate and hepatic pyruvate dehydrogenase levels in rat strains sensitive and resistant to dietary obesity

This study compared the effects of exogenous pyruvate and lactate on the serum levels of pyruvate, lactate, glucose, alanine, and insulin, as well as the activity of hepatic pyruvate dehydrogenase (PDH) in strains of rat that were either sensitive [Osborne-Mendel (OM)] or resistant (S5B/Pl) to high-fat diet-induced obesity. Serum pyruvate and lactate were significantly higher and glucose lower in ad libitum-fed OM rats, but these differences disappeared after an 18-h fast. The increase in pyruvate and lactate after exogenous pyruvate administration was significantly greater in S5B/Pl rats than OM rats. There were no differences in serum alanine with strain or diet. The total PDH activity was similar across strains and diets but the proportion of PDH in its activated form (PDHa) was decreased in ad libitum-fed S5B/Pl rats. Pyruvate injection increased insulin and hepatic PDHa activity in OM rats fed both high- and low-fat diets, but these responses were greatly attenuated or absent in S5B/Pl rats. The data are consistent with the hypothesis that modulation of carbohydrate oxidation by PDH may be related to susceptibility to obesity when rats are fed a high-fat diet.

Role of rat strain in the differential sensitivity to pharmaceutical agents and naturally occurring substances

The development of drugs to combat diseases, chemicals to improve food production, or compounds to enhance the quality of life necessitates, by law, the use of laboratory animals to test their safety. In order to simulate the human condition it is necessary to choose a species in which pharmacokinetic and toxicokinetic mechanisms are established and resemble those of humans. The advantages of the use of the rat in drug and chemical toxicity testing include (a) metabolic pathway similarities to humans; (b) numerous similar anatomical and physiological characteristics; (c) a large database, which is extremely important for comparative purposes; and (d) the ease of breeding and maintenance of animals at relatively low cost. However, the choice of rat can be complicated, especially when over 200 different strains of rat are known to exist. The aim of this review is to summarize genetically determined differences in the responsiveness of rat strains to drugs and naturally occurring chemicals and to show that susceptibility is dependent on the target organ sensitivities, which may also be strain dependent. It is suggested that detailed studies of strain differences may help to clarify toxic mechanisms. Such studies are usually best conducted using inbred strains in which the genetic characteristics have been fixed, rather than in outbred stocks in which individual samples of animals may differ, the phenotype is variable, and the stocks are subject to substantial genetic drift. The fact that strains may differ also needs to be taken into account in assessing the potential hazard of the chemical, particularly when a study involves only a single strain and therefore provides no assessment of likely strain variation.

[Differences in the behavior of organic lesions, immunologic and metabolic parameters in 2 inbred strains of rats]

Two inbred rat strains were obtained by selective breeding and inbreeding: IR (isoprenaline resistant) and IS (isoprenaline sensitive). In addition to known differences between the two strains (1) other differences were found. As compared to IS strain, IR rats were more aggressive and showed more comfort behaviour in open field test. IR rats developed larger stress-induced gastric lesions but smaller heart lesions. They had larger spleen and thymus and more severe arthritis after Freund adjuvans administration. The two strains might be useful in studying the effects of drugs on various pathological processes. Their hybrids are being used to study interrelations between different genetic factors.

Iron and copper metabolism in analbuminaemic rats fed a high-iron diet

The metabolism of iron and copper in male Nagase analbuminaemic (NA) and Sprague Dawley (SD) rats was compared. Relative liver weight was higher and spleen weight significantly lower in NA than SD rats. In NA rats, red blood cell count, haemoglobin and haematocrit were lower, whereas plasma transferrin, total iron-binding capacity and mean corpuscular haemoglobin were higher when compared with SD rats. Iron concentrations in plasma, liver, kidneys and heart were higher, and those in the spleen and tibia were lower, in NA rats. The iron concentrations in liver and spleen were positively correlated with the amount of brown pigment as observed histopathologically. Bile flow as well as biliary iron and copper excretion were higher in NA than SD rats. Copper concentrations in liver, kidneys and plasma were higher in NA rats. Plasma levels of ceruloplasmin were about two-fold higher in NA rats. The feeding of a high-iron diet reduced kidney copper concentrations in both strains of rats, which was associated with a decrease in the absorption and biliary excretion of copper.

Relationship between acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and disturbance of intermediary metabolism in the Long-Evans rat

The aim of this study was to examine the acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin, (TCDD) in a rat strain other than the Sprague-Dawley (S-D) rat, for which most of our data have been generated thus far. Doses for the biochemical study were selected based on an acute range-finding study, which indicated that Long-Evans (L-E) rats are somewhat less susceptible to TCDD toxicity than are S-D rats. Male L-E rats were dosed orally with 10, 20, 45, 67, 100 and 150 micrograms/kg TCDD. Body weight and feed intake were dose-dependently decreased prior to killing of the animals. Eight days after dosing, animals were killed and tryptophan, total T4 (TT4) and total T3 (TT3) levels were determined in serum, whereas the activities of ethoxy-resorufin-O-deethylase (EROD), phosphoenolpyruvate carboxykinase (PEPCK), gamma-glutamyl transpeptidase (gamma-GT) and tryptophan 2,3-dioxygenase (TdO) were measured in liver. EROD activity was fully induced at all doses studied, indicating that as in S-D rats, Ah-receptor-mediated effects do not seem to play any major role in the acute toxicity of TCDD in this rat strain either. Hepatic PEPCK activity was dose-dependently decreased in a similar dose range as in S-D rats, indicating inhibition of gluconeogenesis. Feed intake was dose-dependently decreased as a result of a dose-dependent elevation in serum tryptophan levels, which in turn were related to reduced liver TdO activity. Hepatic gamma-GT activity was also dose-dependently reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Clorgyline effect on pineal melatonin biosynthesis in Roman high- and low-avoidance rats

Pineal melatonin and related indoles levels were higher in Roman high- than in Roman low-avoidance rats, while 5-HIAA/5-HT ratio, as an index of MAO activity was higher in low- than in high-avoidance rats. Clorgyline stimulated pineal melatonin biosynthesis in both lines of rats. However, melatonin and N-acetylserotonin levels remained higher and 5-HIAA levels remained lower in the high avoidance rats treated with low dose (0.5 mg/kg) while treatment with 1.0 mg/kg of clorgyline eliminated the differences in melatonin production between high- and low-avoidance rats.

Increased cyclic guanosine monophosphate production and overexpression of atrial natriuretic peptide A-receptor mRNA in spontaneously hypertensive rats

Atrial natriuretic peptide (ANP) specifically stimulates particulate guanylate cyclase, and cyclic guanosine monophosphate (cGMP) has been recognized as its second messenger. Spontaneously hypertensive rats (SHR) have elevated plasma ANP levels, but manifest an exaggerated natriuretic and diuretic response to exogenous ANP when compared to normotensive strains. In isolated glomeruli, the maximal cGMP response to ANP corresponds to a 12- to 14-fold increase over basal levels in normotensive strains (Wistar 13 +/- 2; Wistar-Kyoto 12 +/- 2; Sprague-Dawley 14 +/- 2) while a maximal 33 +/- 3-fold elevation occurs in SHR (P < 0.001). This hyperresponsiveness of cGMP is reproducible in intact glomeruli from SHR from various commercial sources. Furthermore, this abnormality develops early in life, even before hypertension is clearly established, and persists despite pharmacological modulation of blood pressure, indicating that it is a primary event in hypertension. In vitro studies have revealed a higher particulate guanylate cyclase activity in membranes from glomeruli and other tissues from SHR. This increase is not accounted for by different patterns of ANP binding to its receptor subtypes between normotensive and hypertensive strains, as assessed by competitive displacement with C-ANP102-121, an analog which selectively binds to one ANP receptor subtype. The hyperactivity of particulate guanylate cyclase in SHR and its behavior under basal, ligand (ANP), and detergent-enhanced conditions could be attributed either to increased expression or augmented sensitivity of the enzyme. Radiation-inactivation analysis does not evoke a disturbance in the size of regulatory elements normally repressing enzymatic activity, while the expression of particulate guanylate cyclase gene using mutated standard of A- and B-receptors partial cDNAs, quantified by polymerase chain reaction (PCR) transcript titration assay, manifests a selective increase of one guanylate cyclase subtype. Our data suggest that in hypertension, genetic overexpression of the ANP A-receptor subtype is related to the exaggerated biological response to ANP in this disease.

The distorted alpha 2-adrenoceptor genotype distribution in F2 populations of Dahl salt sensitive and resistant rats cross

To examine the role of the alpha 2-adrenoceptor gene in the development of genetic hypertensive rats, we tested Dahl salt sensitive (S) and resistant rats (R) for the presence of a restriction fragment length polymorphism (RFLP) in that gene. An RFLP was found between the S and R rats with a human kidney cDNA alpha 2-adrenoceptor probe (alpha 2-C4) and Msp I restriction endonuclease. The alpha 2-C4 probe detected two alleles, S and R, of 3.0 and 2.8 kb in size. The two strains of rats were each homozygous for their corresponding allele. The inheritance of the alleles was investigated by crossbreeding S and R rats and subsequent brother/sister mating of F1 rats. Two hundred and fifteen F2 rats were produced by breeding 14 pairs of F1 rats. An atypical distribution of alpha 2-adrenoceptor genotypes was observed. We found a reduced number of the SS genotype in both males and females of the F2 generation. To investigate the mechanism of this distorted alpha 2-adrenoceptor genotype distribution in the F2 rats of S and R cross, we backcrossed the F1 rats to their S and R parents. The litter size and gender distribution were counted for each breeding colony. Analysis by chi-square test showed that there was no sex difference among the backcrosses. Also, there was no significant decrease in litter size. This excludes the possibilities of fetal demise of S homozygotes and intrauterine selection. Therefore the deficiency of SS genotype may be due to gene recombination or may not be due to the alpha 2-adrenoceptor gene itself, but to the effect of other genes closely linked to the alpha 2-adrenoceptor.

Differences in GH secretion from individual somatotropes in rats genetically selected for fast and slow growth

A reverse hemolytic plaque assay was used to examine effects of selection for fast (F) and slow (S) growth on growth hormone (GH) secretion by individual somatotropes. Anterior pituitaries (AP) from 32 male Charles River CD strain rats selected for F and S growth for 20 generations were used. Four rats per line were used at 4, 6, 8, or 10 wk of age. Body weight (P < 0.0001) of F rats was greater compared with S rats. AP (P < 0.05) were heavier at 8 and 10 wk of age in F compared with S line rats. Percentages of GH-secreting cells were unaffected by age (range = 32.7-35.5%) and line [F = 33.1 +/- 1.2% (SE) vs. S = 34.5 +/- 1.2%] or by human GH-releasing factor (hGRF). At 8 and 10 wk, mean plaque-forming area was greater (P < 0.0001) in F compared with S rats under both nonstimulated (2,704 +/- 202 vs. 1,648 +/- 202 microns2) and hGRF-stimulated secretion (4,503 +/- 202 vs. 2,682 +/- 202 microns2). Results indicate that differences in growth observed in the two lines may be due to a greater secretory capacity of individual somatotropes rather than to a greater percentage of somatotropes or sensitivity of somatotropes to secretagogue.

Localization of MPP+ binding sites in the brain of various mammalian species

The distribution and density of 3H-MPP+ binding sites were studied by in vitro quantitative autoradiography in the brain of the mouse, rat and monkey. The highest levels of 3H-MPP+ specific binding were observed in rat brain. The substantia nigra in rat and monkey, and the anterior caudate-putamen formation in mouse and monkey showed the lowest density of autoradiographic grains. The presence of a relatively high density of MPP+ sites in the hippocampus of all species studied could be of interest to explain some effects of MPTP administration on convulsions caused by chemoconvulsants. The finding of a 60-70% reduction of 3H-MPP+ binding sites in the rat caudate-putamen, on the side of quinolinic acid infusion and no changes after 6-hydroxydopamine lesion of dopaminergic nigrostriatal neurons suggests the presence of these sites mainly on striatal cells. The results suggest that the distribution of MPP+ binding sites in brain would not seem to be related to MPTP toxicity.

An aromatase-associated cytoplasmic inclusion, the "stigmoid body," in the rat brain: I. Distribution in the forebrain

An aromatase-containing neural system was examined in the rat forebrain, using a polyclonal antibody against aromatase-associated human placental antigen X-P2 (hPAX-P2). Numerous dot-like structures, which we have called stigmoid bodies, were immunostained in the preoptico-hypothalamic region, the bed nucleus of the stria terminalis, the medial amygdala, the arcuate nucleus, the subfornical organ, and the area extending from the hypothalamic area to the central gray through the medial forebrain bundle and the periventricular fiber system of the posterior diencephalon. The stigmoid bodies were always found as inclusions in the neuronal cytoplasm. Their diameter was usually 1-3 microns, but exceptionally large forms, over 3 microns, were found in some brain regions, including the area extending from the median preoptic nucleus surrounding the organosum vasculosum laminae terminalis to the anterior medial preoptic nucleus, the periventricular nucleus of the preoptic area, and some parts of the medial preoptic nucleus. Most of these nuclei show sexual dimorphism. The distribution pattern of the hPAX-P2 immunoreactive stigmoid bodies agreed well with that of aromatase activity previously reported in many biochemical studies. Brain regions where the stigmoid bodies were prominent largely coincide with steroid binding locations common to both androgen and estrogen, or regions where both sex steroid receptors are present. Although it still remains to be determined whether aromatase is localized within these stigmoid bodies, it appears likely that they are closely associated with the function of sex steroids at their target sites in the brain.

Comparison of the distribution of carbonic anhydrase isozymes (CA-I, CA-II, CA-III) in the rat gastrointestinal tract

The present paper described the immunohistochemical distributions of carbonic anhydrase (CA) isozymes. CA-I, CA-II and CA-III, in the epithelium lining the rat gastrointestinal tract, with rabbit antibodies to equine CA-I, CA-II and CA-III. Prior to the immunohistochemical examinations, the crossreactivities of these antibodies to the rat-antigens were confirmed in this study. In the stomach, surface epithelial cells and parietal cells of the glandular region showed an immunoreactivity only to CA-II. In the large intestine, each immunoreactivity to CA isozyme (CA-I, CA-II and CA-III) was localized in the upper portion of intestinal glands, and decreased toward the distal digestive tract, but absent in the small intestine. The present histological findings suggested that the CA isozymes might play a role in the ion-transportation during the water absorption in the rat large intestine.

Corticotropin effects on blood pressure and fluid and electrolyte homeostasis in five strains of rats

The hemodynamic and metabolic effects of 11 days of sham (saline) and corticotropin injection were examined in five different strains of rats: Sprague-Dawley, spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), Brattleboro, and Long Evans. Corticotropin significantly increased systolic blood pressure (SBP) compared with sham injection in all strains: final SBP in Sprague-Dawley was 108 +/- 5 mm Hg corticotropin, 94 +/- 4 mm Hg sham; SHR 146 +/- 6 mm Hg corticotropin, 141 +/- 3 mm Hg sham; WKY 117 +/- 3 mm Hg corticotropin, 103 +/- 3 mm Hg sham; Brattleboro 108 +/- 5 mm Hg corticotropin, 93 +/- 2 mm Hg sham; and Long Evans 103 +/- 5 mm Hg corticotropin, 90 +/- 4 mm Hg sham (P less than .001). Corticotropin also produced a decrease in body weight and increases in water intake and urine output. Increases in urine electrolyte excretion were seen in some, but not all strains. The rise in pressure in the Brattleboro rats indicated that vasopressin is not essential for the corticotropin-induced rise in pressure. Blood pressure rises in SHR were not exaggerated. Withdrawal of corticotropin in Sprague-Dawley rats led to rapid reversal of the corticotropin-induced hemodynamic and metabolic changes. Thus, strain does not appear to be an important factor in corticotropin hypertension in the rat, in contrast to deoxycorticosterone hypertension.

Comparison of cadmium, mercury and calcium accumulations by isolated hepatocytes of the small skate (Raja erinacea) and rat

1. Accumulation of calcium, cadmium and mercury by isolated hepatocytes of the small skate (Raja erinacea) and rat was examined at 14 and 37 degrees C, respectively. 2. Metal uptakes by both species were biphasic, with rat cells accumulating more metal than the skate cells. 3. Total accumulation after 30 min was in the order: mercury = cadmium much greater than calcium. 4. In both species calcium and cadmium accumulations were reduced at 4 degrees C, while mercury accumulation was not. 5. Cd accumulation was increased by Cu and Hg in both species. 6. Hg accumulation was inhibited by Cu in both species, and increased by Cd only in the rat cells.

Ontogeny of gene expression of adenosine A2 receptor in the striatum: early localization in the patch compartment

The ontogeny of adenosine A2 receptor mRNA and adenosine A2 binding sites distributions was studied by in situ hybridization histochemistry and receptor autoradiography in pre- and post-natal rat striatum, postnatal dog striatum, and a human fetus striatum and compared to that of dopamine D1 and mu opiate receptors. The early postnatal striatum demonstrated heterogeneous distributions of adenosine A2 receptor mRNA and adenosine A2 binding sites with patches of dense labeling corresponding to dopamine D1 and mu opiate receptors enriched zones. This patchy pattern evolved to the homogeneous distribution observed in the adult. The higher intensity of adenosine A2 receptor mRNA enriched patches correspond at the microscopical level to a higher density of labeled neurons in the patches areas and also to a higher level of expression per labeled patches neuron than in the matrix ones. This demonstrates for the first time that differences in patch/matrix receptor density is at least partly linked to different levels of receptor gene expression.

Magnesium distribution in rats after maximal exercise in air and under hypoxic conditions

Variations in serum levels and distribution of Mg in the heart, gastrocnemius, liver and kidney in rats were studied after exercise to exhaustion in air (normoxia) and during hypoxia (FIO2 = 0.10). After exercise serum Mg concentrations increased significantly in air, but not during hypoxia. At rest, they increased significantly during hypoxia. In air, increases in Mg in the gastrocnemius and liver were found after exercise. At rest in hypoxia, Mg was reduced in heart, liver and kidney. After exercise in hypoxia, Mg was decreased in heart, gastrocnemius and liver, the greatest decrease occurring in the gastrocnemius, with a relative increase in kidney. Exercise and hypoxia both affect magnesium homeostasis.

Increased cotinine elimination and cotinine-N-oxide formation by phenobarbital induction in rat and mouse

The metabolic fate of cotinine, the major metabolite of nicotine, was studied in phenobarbital-induced and non-induced isolated perfused rat lung and liver and in isolated hepatocytes of rats and mice. The non-induced lung tissue showed low cotinine metabolizing capacity while the perfused liver was approximately four times more active. After phenobarbital pretreatment the metabolism of cotinine was increased eight-fold in the intact liver. A substantial increase in cotinine metabolism was also found in isolated hepatocytes from PB-induced rats and in cultured mouse hepatocytes grown in a medium supplemented with PB. This was paralleled by an increased formation of cotinine-N-oxide which could be inhibited by 100 microM metyrapone. In contrast, the pulmonary elimination of cotinine was not affected by PB. A dominant role of primary N-oxidation of nicotine compared to C-oxidation was apparent in non-induced rat liver. After PB treatment the rate of nicotine-N'-oxide formation dropped markedly while the cotinine related pathways were increased causing an inversion of the N- to C-oxidation ratio. In the lung, cotinine formation was the preferred metabolic pathway of nicotine already in non-induced organs. The pattern of nicotine metabolites was not altered by PB induction. In conscious PB-induced rats receiving nicotine orally or intravenously, 3'-hydroxycotinine was found as the main urinary metabolite of nicotine while only a small fraction was excreted as cotinine-N-oxide. This discrepancy between the profile of nicotine metabolites in perfused liver and lung and in the urine in vivo indicates that extrahepatic organs other than the lung may be important sites of cotinine metabolism.

Metabolic activity in isolated hepatocytes from cold exposed rats subjected to 24-hour fasting

The aim of this work was to study the metabolic activity in isolated hepatocytes from control rats and rats exposed for 15 or 30 days to cold, all subjected to 24-h fasting. Hepatocyte oxygen consumption was used as an index of metabolic activity. The results show that 24-h fasting induces a decrease in energy expenditure at the level of the liver in cold-exposed rats but not in control animals.

Ontogeny of histamine-immunoreactive cells in rat stomach

An antiserum against hemocyanin-conjugated histamine was used to study the cellular stores of histamine in the stomach, especially the oxyntic mucosa, of fetal and early postnatal rats. Tissues were fixed in 4% 1-ethyl-3(3-dimethyl-aminopropyl) carbodiimide (EDC-DI) and standard immunofluorescence technique was used. Histamine was first detected on the 16th embryonic (E16) day when a few histamine-immunoreactive (HA-ir) cells and nerve fibers were observed in the muscular layer of the stomach wall. On day E18, HA-ir cells were visualized for the first time in the oxyntic mucosa of the stomach, and from that day on the number of such cells increased slowly initially and after day E20 more rapidly. At birth many of the HA-ir cells in the oxyntic mucosa possessed processes giving them a paracrine-like appearance typical of enterochromaffin-like cells (ECL cells). Only a very small number of the HA-ir cells represented metachromatically stained mast cells and were located in the submucosa. After birth, the number of HA-ir ECL cells increased steadily, until day 21 when the distribution and number was very similar to that of the adult. The results suggest that histamine-containing neurons and ECL cells appear in the stomach wall before birth, and that there are histamine-containing ECL cells in the mucosa and mast cells in the submucosa of the stomach wall at birth.

Vasoactive intestinal polypeptide and acetylcholine coexist with neuropeptide Y, dopamine-?-hydroxylase, tyrosine hydroxylase, substance P or calcitonin gene-related peptide in neuronal subpopulations in cranial parasympathetic ganglia of rat

Immunohistochemistry has been used to demonstrate that neuropeptide Y, dopamine-beta-hydroxylase, calcitonin gene-related peptide or substance P are colocalized with vasoactive intestinal polypeptide and choline acetyltransferase in subpopulations of neurons in cranial parasympathetic ganglia of rat. These comprise the ciliary, sphenopalatine, otic, glossopharyngeal-vagal and internal carotid ganglia. In the ciliary and glossopharyngeal-vagal ganglia tyrosine hydroxylase is also found in such neurons. The findings emphasize that the combined localization of dopamine-beta-hydroxylase and neuropeptide Y or the presence of tyrosine hydroxylase is not exclusively a marker for peripheral adrenergic neurons. Further, the co-localization of calcitonin gene-related peptide and substance P is not a decisive indication that a neuron is sensory in nature. It is discussed whether the presence of the enzymes and peptides other than vasoactive intestinal polypeptide is a remnant of a different expression during ontogenesis or indicates target-specific functions in the adult.

Postnatal development of von Ebner's glands: accumulation of a protein of the lipocalin superfamily in taste papillae of rat tongue

Antibodies produced against rat von Ebner's gland (VEG) protein, a recently characterized member of a lipophilic ligand carrier protein family, detect this protein immunocytochemically in von Ebner's gland acini and show that it is present at high concentrations in the clefts of circumvallate and foliate papillae. During embryonic development, von Ebner's gland anlagen are innervated (as shown immunocytochemically using neuronal specific antibodies) as early as embryonic day 20, before lateral glandular outgrowth and VEG protein can be observed. Expression of the VEG protein as determined by in situ hybridization and immunocytochemistry begins at postnatal day-2 cells in differentiating and branching off from von Ebner's gland ducts, and sharply increases with further enlargement and maturation of the gland. The close temporal correlation of von Ebner's gland innervation and VEG protein expression with papilla innervation and taste-bud development suggests a functional relationship of both structures. VEG protein might control access of lipophilic sapid molecules, such as bitter substances, to the gustatory receptors.

Distribution of histamine in the rat kidney during pregnancy and development

An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.

Quantification of the sulphomucin-producing cell population of the colonic mucosa during protracted stress in rats

The sulphomucins contained in goblet cells of the descending colon of 55 Sprague-Dawley rats were histochemically labelled by High Iron Diamine (HID) and quantified in an image analyzer (Cortex controller). After transportation to the stress laboratory, 25 rats were compelled to swim for two consecutive hours/day either only once (5 rats), for one week (5 rats), two weeks (5 rats), four weeks (5 rats) or eight weeks (5 rats). 25 additional rats were only transported to the stress laboratory (i.e. "sham-handled" control), either once (5 rats), for one week (5 rats), two weeks (5 rats), four weeks (5 rats) or eight weeks (5 rats). The remaining 5 rats were "untransported", resting control rats (i.e. day zero). The results were expressed in percent of HID-staining/total mucosa analyzed. When various time intervals were compared with those of day zero (i.e. horizontal study), it was found that one day swimming rats had a significantly lower percentage (p less than 0.001) of HID stained material. The fluctuations at other time intervals were non-significant. On the other hand, for transported rats, a significant increase (p less than 0.001) in the percentage of HID positive areas was found for rats swimming for eight weeks. When compared to day one, the percentage of HID positive areas increased from day one to one-eight weeks, the differences being significant (p less than 0.001) at four and (p less than 0.01) eight weeks. Similar results were found for transported rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional cerebral glucose metabolism compared in rodents and humans

In order to compare regional brain glucose metabolism in rats and humans, this parameter was measured using Sokoloff's deoxyglucose method in rats, and positron emission tomography with magnetic resonance imaging in humans. An atlas of cerebral regions of interest common to both species was developed to facilitate the evaluation of the relationship in regional values. We found among the regions studied a significant positive correlation in their metabolic values (r = 0.72, P less than 0.001) and coefficients of variation (r = 0.59, P less than 0.01) suggesting that regional brain glucose consumption is comparable between rat and human. Results of this study support the view that rat and human brain may be phylogenetically linked functionally as well as anatomically.

Acidic fibroblast growth factor (aFGF)-like immunoreactivity in the optic nerve

Acidic fibroblast growth factor (aFGF)-like immunoreactivity was examined in the optic nerves of 1- to 25-month-old Wistar rats, 0.5- to 7-year-old bovine animals and normal human adults (24 and 35 years old), using cryostat sections incubated with a rabbit polyclonal antibody specific for aFGF. The immunoreactivity was associated with glial cells, and was localized predominantly in the nucleus. The presence of endogenous aFGF in the optic nerve of adult subjects and 'old' rats suggests that aFGF could play a role in the survival of retinal ganglion cells and their axons during aging.

An ATP-driven Cl- pump regulates Cl- concentrations in rat hippocampal neurons

To investigate the role of Cl(-)-stimulated Mg(2+)-ATPase (Cl(-)-ATPase) in neurons, we examined the effects of ethacrynic acid (0.3 mM), which completely inhibits Cl(-)-ATPase on the intracellular Cl- concentrations of cultured rat hippocampal neurons, using Cl(-)-sensitive fluorescent probes. Ethacrynic acid and ATP consuming treatment increased the intracellular Cl- concentration, but elevation of the extracellular K+ concentration up to 10 mM, inhibition of Na+/K(+)-ATPase, or dissolution of H+ gradients had no effect. Furosemide (0.1 mM), an inhibitor of Na+/K+/Cl- co-transport, decreased the intracellular Cl- concentrations. These results indicate that an ethacrynic acid-sensitive and ATP-driven Cl- pump functions to reduce intraneural Cl- concentrations.

Major differences in CNS sulfonylurea receptor distribution between the rat (newborn, adult) and turtle

Our previous results have shown that KATP channels play an important role in K+ efflux and extracellular K+ accumulation in the rat brain, and this role was quantitatively more important in the adult than in the newborn brain. The purpose of this study was to localize by autoradiographic techniques the binding sites of glibenclamide, a potent sulfonylurea ligand that targets KATP channels, in the adult and newborn rat central nervous system (CNS). Since the adult turtle is resistant to anoxia, we also compared the rat to the turtle brain sulfonylurea receptor distribution. In all three animal groups (newborn rat, adult rat, adult turtle), specific glibenclamide binding was saturable. Scatchard plots were curvilinear in the rat, thus suggesting that glibenclamide binds to two types of sites, i.e., high and low affinity sites. Scatchard analysis on turtle brain tissue showed evidence of one binding site only. We also found that the distribution of glibenclamide binding sites was heterogeneous in the adult rat CNS with a higher density in rostral than in caudal regions. The highest binding densities were seen in the cortex, hippocampus, cerebellum, substantia nigra, and a few thalamic nuclei; intermediate densities were observed in the basal ganglia, septum, thalamus, and the hypoglossal nucleus. There was a low density in most areas of the hypothalamus, midbrain, brainstem, and spinal cord. Compared with the adult rat, the newborn had a very homogeneous distribution of binding sites and densities were very low throughout the CNS; the level of binding density was even lower in some regions undetectable in the adult turtle. Our results indicate that (1) there are high and low affinity sulfonylurea receptors in the rat CNS, (2) there is a striking heterogeneity in the distribution and density of sulfonylurea receptors in the adult rat CNS and this is in sharp contrast to the homogeneous distribution and low density in both newborn rat and adult turtle; (3) sulfonylurea receptors increase in number postnatally in the rat since binding density increases and the Kd in the newborn rat is similar to that in the adult rat. We speculate that KATP channels and sulfonylurea receptors are poorly developed in the turtle and develop mostly after birth in the rat, reaching highest density in adulthood.

Increased nuclear type II estradiol receptor concentrations in rat spleen during the course of pregnancy

Estradiol receptors are classified into type I and type II receptors by their affinity and capacity for estradiol binding. The type II receptors are thought to be significant in the suppression of immune response, such as in the pregnancy-associated immunosuppression. The present study was undertaken to show the presence of type II receptors in rat spleen and to examine the change of receptor distribution after estradiol administration and during pregnancy. Scatchard analysis revealed that the type II receptors were present in rat spleen, and dissociation constants were estimated to be 3.23 x 10(-9) M for cytosol and 4.29 x 10(-9) M for nuclei. The receptors possessed specificity for estradiol and diethylstilbestrol, but not for promegestone, methyltrienolone and dexamethasone. Administration of estradiol to rats resulted in the increase of nuclear receptor concentrations with concomitant decrease of cytosolic concentrations. During pregnancy, the receptor concentrations were increased in the nuclear fraction, but were not significantly changed in the cytosolic fraction. The dissociation constants of the receptors in pregnant rat spleen (4.77 x 10(-9) M for cytosol and 7.20 x 10(-9) M for nuclei) were similar to those in the non-pregnant control, suggesting the quantitative change of the receptors during pregnancy.

Alternative splicing of rat tropoelastin mRNA is tissue-specific and developmentally regulated

Sequence analysis of cDNA clones coding for rat tropoelastin previously has identified two variants that potentially corresponded to alternatively spliced tropoelastin mRNAs (Pierce et al., 1990). We have now used S1 nuclease protection analysis of total RNA from aorta, skin and lungs of 10-day and 6-week old rats to localize all sites of alternative splicing in the tropoelastin mRNA and to examine tissue-specific and developmental regulation of the use of these sites. This analysis revealed multiple sites of alternative splicing involving rat tropoelastin coding sequences corresponding to exons 12 through 15 of the bovine tropoelastin gene and a single site of alternative splicing at sequences corresponding to exon 33. Messenger RNAs from all three tissues at both developmental stages were alternatively spliced at the same sites; there was no evidence for the use of an alternative splice site unique to a particular tissue or developmental stage. However, both tissue-specific and developmentally regulated differences were apparent in the proportion of rat tropoelastin mRNA alternatively spliced at exon 33. Tropoelastin mRNA from the aorta and lungs of neonatal rats was alternatively spliced at exon 33 ten time more frequently than tropoelastin mRNA from skin. Between 10 days and 6 weeks of development, the use of this site of alternative splicing decreased by twenty-fold in RNA from skin, ten-fold in RNA from lungs and two-fold in RNA from aorta. In contrast, alternative splicing at exons 12 through 15 occurred in a small percentage of the mRNA and use of these sites exhibited minimal tissue-specific differences or developmental regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

No promotion of urinary bladder carcinogenesis by sodium L-ascorbate in male ODS/Shi-od/od rats lacking L-ascorbic acid-synthesizing ability

The promoting effects of sodium L-ascorbate (Na-AsA) on two-stage urinary bladder carcinogenesis were investigated in male ODS/Shi-od/od rats. This strain genetically lacks L-ascorbic acid-synthesizing ability, which is controlled by a single autosomal recessive od gene; heterozygous ODS/Shi(-)+/od, normal ODS/Shi(-)+/+ or F344 rats are able to synthesize L-ascorbic acid. In experiment 1, ODS/Shi-od/od and F344 rats were given 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in their drinking water for 2 weeks and then basal CA-1 diet with or without 5% Na-AsA for 32 weeks. F344 rats were sensitive to the promoting effects of Na-AsA, whereas ODS/Shi-od/od rats were resistant. Administration of Na-AsA increased the urinary pH and the urinary concentrations of Na+ and total ascorbic acid in all strains. In experiment 2, DNA synthesis in the urinary bladder epithelium of F344 rats fed MF diet or CA-1 diet was increased by exposure to 5% Na-AsA for 8 weeks, but not in ODS/Shi-od/od rats fed CA-1 diet. In experiment 3, ODS/Shi-od/od, ODS/Shi(-)+/od and ODS/Shi(-)+/+ rats were given 0.05% BBN for 4 weeks and then CA-1 diet with or without 5% Na-AsA for 32 weeks. ODS/Shi-od/od, ODS/Shi(-)+/od and ODS/Shi(-)+/+ rats were resistant to the promoting effects of Na-AsA in two-stage urinary bladder carcinogenesis. The urinary pH and the urinary concentrations of Na+ and total ascorbic acid in ODS/Shi-od/od, ODS/Shi(-)+/od and ODS/Shi(-)+/+ rats were increased by the administration of Na-AsA. These results indicate that ODS/Shi-od/od rats are resistant to the promoting effects of Na-AsA in two-stage urinary bladder carcinogenesis, and that the susceptibilities of ODS/Shi-od/od rats are regulated by genes different from the gene at the od locus.

The subunit proportions and kinetic properties of 6-phosphofructo-1-kinase isozymes from rat heart atria and ventricle progressively change during aging

Relative to 2-3 month rats, total 6-phosphofructo-1-kinase (PFK) activity in heart atria from 12 month rats declined 31%; but, by 24 months it was decreased by only 13%. PFK activities from 12 and 24 month ventricles relative to the 2-3 month rats were decreased by 40% and 30%, respectively. This change in PFK activity in each heart region was associated with alterations of subunit composition. In heart atria from 12 and 24 month rats when compared to 3 month rats, the levels of L-type subunit were not significantly different; but the levels of the M-type subunit were decreased by 43% and 38%, respectively. With respect to levels in 2-3 month atria, the C-type subunit in 12 month atria decreased by 27%; and at 24 months it increased by 31%. Making the same comparison for the heart ventricle at 12 and 24 months, L-type subunit decreased by 30% and 24% respectively; M-type subunit decreased by approximately 47%; and the C-type subunit increased 1.9 and 4.7 fold, respectively. These age-related changes of subunit composition in atrial and ventricular PFK isozyme pools led to changes in their kinetic and regulatory properties suggesting that the aged rat could exhibit a diminished capacity to produce ATP from glucose.

Serotonin-positive fibers within the spinal motor nucleus of the newborn rat, with special reference to co-localization of substance P

Developmental changes of serotonin-positive fibers with special reference to co-localization with substance P was examined immunohistochemically in the ventral horn of rat lumbar spinal cord. Only about 20% of serotonin-positive fibers co-labelled with substance P on postnatal day (P) 0. The ratio of co-localization gradually increased, and reached the adult value by P28 (60-70%). Enkephalin-positive fibers were not co-localized with serotonin at any age examined. Although the densities of serotonin, substance P and enkephalin per unit area of the ventral horn gradually increased with development up to P28, the density of serotonin in the adult was decreased compared to P28 animals.

Sensory responses, dietary-induced obesity and biochemical values in Sprague-Dawley rats

Food intake and body weight gain variability in Sprague-Dawley (SD) rats exposed to a palatable high-fat diet were examined in relation to sensory responses and biochemical parameters in two experiments. In the first experiment, varying sucrose concentrations (4-32% wt./vol.) were randomly presented for 20 minutes to ad lib chow-fed rats. Each rat's sensory response was expressed as Beta (B), or the slope of the regression between solute intake and concentration, and used to assign rats to diet groups. In the second experiment, responsiveness to fat emulsions (1-37%) were similarly measured and categorized. In both experiments sensory responses to sucrose were significantly related to weight gain/fatness on the high-fat diet (lab chow-corn oil). Sensory responsiveness to the fat emulsions was unrelated to sucrose responsiveness or to high-fat feeding. Biochemical parameters (insulin, cholesterol, triglycerides, lipoproteins) reflected increased caloric (fat) intake, as well as sucrose responsiveness. Predictors (sensory responses, biochemical values) of response to chronic (4 months) or short-term (less than 2 months) high-fat diets are discussed.

Comparison of the disposition and of the metabolic pattern of Reboxetine, a new antidepressant, in the rat, dog, monkey and man

The purpose of this study was to compare the disposition and the metabolic pattern of Reboxetine in several species, including man. [14C]-Reboxetine was given orally to the rat, the dog, the monkey (5 mg/kg) and man (2 and 4 mg/kg). Radioactivity was eliminated both by the renal and faecal route in the rat and the dog, mainly in urine in the monkey and man. Reboxetine was extensively metabolized. A number of urinary metabolites were quantified by radio-HPLC and tentatively identified by comparison with the retention times of reference compounds. Suggested routes of metabolic transformation are: 2-O-dealkylation; hydroxylation of the ethoxyphenoxy ring; oxidation of the morpholine ring; morpholine ring-opening; and combinations of these. Metabolites were partially or completely conjugated with glucuronic acid and/or sulphuric acid.

Mapping of glial fibrillary acidic protein-immunoreactivity in the rat forebrain and mesencephalon by computerized image analysis

Computer-assisted image analysis was used to map the regional distribution of glial fibrillary acidic protein-immunoreactive (GFAP-IR) astrocytes in the rat forebrain and mesencephalon. A complete survey of packing densities of GFAP-IR structures was performed. Computer maps revealed high values in the outer and inner layers of the cortex, some hippocampal and olfactory bulb layers, prepiriform cortex, dorsal part of the caudate-putamen, globus pallidus, lateral septum, reticular thalamic nucleus, lateral habenular nucleus, circumventricular organs, nuclei of the medial hypothalamus, substantia nigra, interpeduncular nucleus, and mamillary body. These correspond to regions of the embryonic pial and ventricular brain surfaces, which undergo developmental alterations including growth and various forms of internalization. From this we conclude that in the adult brain, astrocytes of high GFAP-IR are derivatives of surface-contact glia, whereas those located in areas having developed by the local thickening of the neural tube wall show reduced or no GFAP-IR.