Developmental and Tissue-Specific Modulation of Rat Galactose-1-Phosphate Uridyltransferase Steady State Messenger RNA and Specific Activity Levels

Abstract

ABSTRACT. To assess the role of genetic regulation as a state levels of GALT sp act (7). In this report, we have assessed modulating factor in the variability of rat tissue galactose-GALT sp act and steady state mRNA during postnatal rat liver I-phosphate uridyltransferase (GALT) sp act, we have development and in various tissues of the adult rat. Our findings determined steady state GALT mRNA and sp act in rat that there is a correlation between the two parameters in these liver during postnatal development. Steady state GALT investigations indicates that genetic regulation plays an impormRNA levels increase from birth to d 5 and subsequently tant role in modulating GALT activity. Our findings form the decrease toward adult levels. GALT sp act mirrors the basis of this report. mRNA pattern. A survey of steady state mRNA and GALT sp act of several adult rat tissues revealed marked tissue differences with a good correlation of the two parameters. MATERIALS A N D M E T H O D SLiver had the highest GALT mRNA and sp act; kidney, ..lnimul.s. Timed pregnant Sprague-Dawley rats from Charles ovary, a_nd heart had similar but lower mRNA and sp act; River Breeding Farms (Wilmington. MA) were housed three per skeletal muscle and testes had the least GALT mRNA and cage with free access to food and water in a room with a 10: 14 enzyme sp act. These findings suggest that genetic regu-h 1ight:dark cycle. All experiments were performed using the lirtion is important in the variable expression of GALT Children' Chomczynski and Sacchi (8). One hundred mg of tissue were homogenized using a Dounce homogenizer in 1 The metabolism of galactose, a major carbohydrate constituent mL of 4 M guanidinium thiocyanate. 25 mM sodium citrate. of almost all animal milk, is controlled by the three enzymes of pH 7, 0.5% SDS, and O.' 2-mercapt0ethan01. The tissue was the Leloir pathway, galactokinase, GALT, and UDP galactose-transferred to a ~ol~pr0pYlene tube and sequentially extracted 4-epimerase ( 1). ~h~~ GALT is a key enzyme in the pathway is with acidified phenol and chloroform-isoamyl alcohol (49: 1). highlighted by human galactosemia due to deficient GALT ac-The RNA was precipitated with isopropanol and resuspended in tivity. Interest in this recessively inherited disorder has fostered 1 mL of dieth~l~~rocarbonate-treated water. The RNA concenefforts to delineate the mechanism responsible for regulation of tration was determined by at 260 nm UV.GALT activity. We have previously described increases in liver Separate Northern blots of RNA obtained from newborn rat GALT sp act in rats fed a highegalactose diet (2). in pregnant liver and adult rat tissues were generated by electrophoresis of female rat liver, possibly related to progesterone (3. 4), and in l o pg RNA a I% agarOse-fomaldehYde gel the postnatal development of rat liver (5). We have also described by a Zetabind membrane (CUNO. variation of GALT sp act in different rat tissues (5) and modu-Meriden, CT). The RNA was fixed to the membrane using a lation by uridine nucleotides (6). ...

Expression of Galactose-1-Phosphate Uridyltransferase in the Anterior Pituitary of Rat during the Estrous Cycle

“…Data obtained from various tissues of adult and devel oping rats [2][3][4][5] clearly demonstrated that the pattern of GALT mRNA reflects the GALT-specific enzymatic ac tivity and the genetic regulation of this modulation. Thus one can assume that this may be also true for the rat ante rior pituitary in which GALT mRNA and protein expres sion is reported here for the first time.…”

“…GALT-specific enzy matic activity and activation of galactose metabolism. This has been demonstrated in the liver during postnatal development [2,3] and in response to a high galactose diet [4], GALT mRNA expression has also been shown to be correlated to GALT enzymatic activity investigated in different regions of rat brain [5] and various other tissues, including testis and ovary from adult rats [3], In the present study we concentrated on GALT mRNA and protein expression in rat anterior pituitary at differ ent stages of the estrous cycle. Levels of synthesis of pitu itary gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) change during estrous cycle, with a translational peak during diestrus [6][7][8][9][10][11] and a transcriptional peak in proestrus and early estrus [7][8][9], The peak of LH and of FSH release occurs during late proestrus and estrus [12,13].…”

The effect of systemic and ovarian infusion of glucose, galactose and fructose on ovarian function in sheep

“…These in vitro findings therefore suggest that galactose is exerting its inhibitory effects on ovarian function through granulosa cell function although we have also been able to show that both granulosa and theca cells express the galactose transporter SLC2A8 (GLUT8; Onions et al 2009. Further, galactose can also be utilised as a substrate for the synthesis of essential factors such as nucleotide sugars (Heidenreich et al 1993, Liu et al 2000 and therefore may have local actions at multiple levels.…”

“…In ruminants, fructose is thought to be rapidly metabolised to glucose in the liver (Luick et al 1957), which may then trigger insulin release, but in primates and humans, fructose has been reported to have little effect on insulin and leptin release or on the concentrations of blood glucose (Curry 1989, Havel 1997, Teff et al 2004. In contrast, enzymes involved in the metabolism of galactose are abundantly and actively expressed in the ovary (Heidenreich et al 1993) and in humans ovarian dysfunction is observed in individuals with deficiencies or mutations in these enzymes (Liu et al 2000). In ruminants, however, the supplementation of diets high in galactose, such as those containing lupin grain (van Barneveld 1999), stimulates folliculogenesis and increases fecundity in ewes (Knight et al 1975) although evidence of the effects of this intervention on insulin concentrations is equivocal (Munoz-Gutierrez et al 2002, Somchit et al 2007.…”

The effect of monosaccharide sugars and pyruvate on the differentiation and metabolism of sheep granulosa cells in vitro

“…The supplementation of diets with lupins, which are high in galactose (van Barneveld 1999), stimulated folliculogenesis and increased fecundity in ewes (Knight et al 1975). Enzymes involved in the metabolism of galactose are abundantly and actively expressed in the ovary, implicating it as a site of uptake, metabolism and utilisation (Heidenreich et al 1993). Furthermore, significant plasma-follicular fluid concentration gradients in the human preovulatory follicle also suggest that galactose is both taken up and directly metabolised by ovarian follicles (Jozwik et al 2007).…”