Phosphoenolpyruvate Carboxykinase of Rat Small Intestine: Distribution and Regulation of Activity and mRNA Levels

Watford, Malcolm; Tatro, Alicia V.

doi:10.1093/jn/119.2.268

Cited by 15 publications

(12 citation statements)

References 28 publications

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“…2) [16]. This observation is similar to the diabetes-induced increase in the number of transcripts for intestinal phosphoenolpyruvate carboxykinase which was not matched by any comparable increase at the protein level [52].…”

Section: Resultssupporting

confidence: 54%

Diabetes‐induced changes in guanine‐nucleotide‐regulatory‐protein mRNA detected using synthetic oligonucleotide probes

Griffiths

Knowler

Houslay

1990

European Journal of Biochemistry

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Synthetic oligonucleotide probes were designed to detect the α‐subunits of the guanine‐nucleotide‐regulatory proteins (G‐proteins) Gi‐1, Gi‐2, Gi‐3 and Gs (Gi is inhibitory and Gs is stimulatory). Each probe detected a single major mRNA species in Northern blots of RNA extracted from a variety of tissues. A probe was designed to identify the two forms of G‐protein β‐subunits, β1 and β2. This probe hybridised with a single 1.8‐kb transcript (β2) in RNA from all tissues studied except for brain, where a less‐abundant 3.4‐kb transcript (β1) was also detected. These probes were used to assess whether the induction of diabetes, using streptozotocin, altered the levels of mRNA coding for specific G‐protein components. In hepatocytes, diabetes caused a significant reduction in the number of transcripts coding for α‐Gs, α‐Gi‐2 and α‐Gi‐3; mRNA for α‐Gi‐1 was undetectable. In adipocytes, diabetes increased dramatically the mRNA coding for α‐Gi‐1 and α‐Gi‐3, whilst no significant changes occurred in the fractions coding for α‐Gi‐2 and α‐Gs. No significant changes in the mRNA coding for G‐protein α‐subunits were observed in either brain, heart, skeletal muscle or kidney. Diabetes did not cause any significant changes in the mRNA coding for β2 in any tissue or cell population studied. Such results on the relative levels of mRNA encoding G‐protein components was obtained by comparing equal amounts of total RNA from tissues of control and diabetic animals. G‐protein mRNA levels were expressed relative to ribosomal 28S RNA levels and, in some instances, relative to transcripts for a structural protein called CHO‐B. The total cellular levels of both RNA and DNA were assessed in the various tissues and cells studied. Major falls in RNA levels cell appeared to occur in hepatocytes and to a lesser extent in adipocytes and skeletal muscle. Thus major reductions in G‐protein transcripts occurred in hepatocytes. The detected changes in G‐protein mRNA are discussed in relation to the available evidence on G‐protein expression. We suggest that diabetes causes tissue‐specific changes in the levels of mRNA for particular G‐protein species; this may have consequences for the functioning of cellular signal‐transduction mechanisms in the affected tissues.

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Section: Resultssupporting

confidence: 54%

Diabetes‐induced changes in guanine‐nucleotide‐regulatory‐protein mRNA detected using synthetic oligonucleotide probes

Griffiths

Knowler

Houslay

1990

European Journal of Biochemistry

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“…Expression of β-actin and GAPDH mRNA, which are frequently used as internal standards for mRNA levels, were elevated 2-to 3-fold, while that of albumin mRNA decreased drastically after the two 5 day periods of fasting. Previous studies have demonstrated a decrease in the levels of some mRNA species in rat liver after various periods of fasting (60,61), but the levels of other mRNA species increase in liver (62) and small intestine (63) when rats are fasted for up to 7 days. Others have reported significant decreases in functional albumin mRNA upon shortterm fasting (64).…”

Section: Discussionmentioning

confidence: 92%

The effect of short-term fasting, phenobarbital and refeeding on apoptotic loss, cell replication and gene expression in rat liver during the promotion stage

Hikita

Nuwaysir²,

Vaughan³

et al. 1998

Carcinogenesis

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Previous work from this laboratory has reported on the effects of two sequential 5 day periods of fasting and subsequent refeeding on tumor promotion in multistage hepatocarcinogenesis in the rat (Carcinogenesis, 18, 159-166, 1997). In the present extension of the earlier study, the sequential fasting-refeeding regimen was begun at later time points (28 and 54 days post-initiation) than the first study. This was done to determine whether larger-sized altered hepatic foci (AHF) exhibited a depletion similar to that of the relatively small AHF in the published experiment and to study concomitant molecular changes during the fasting periods. Groups of animals were fasted in the presence and absence of 0.05% phenobarbital (PB) in the drinking water. During the fasting periods, both body and liver weights decreased dramatically, less in the fast begun at 54 days. This change was accompanied by a significant decrease in the bromodeoxyuridine (BrdU) labeling indices of hepatocytes within AHF. Apoptotic bodies increased dramatically in the non-focal (surrounding the AHF) hepatocytes during the fasting periods. These parameters were slightly lower in hepatocytes of rats administered PB during the fasting periods, most notably during the 54-66 day period. With the nick end-labeling method, the proportion of hepatocytes undergoing apoptosis was significantly higher in cells within AHF at the end of each of the fasting periods in all but one group. Concomitantly, the number of AHF and percentage of liver volume occupied by AHF decreased dramatically during the fasting periods. Refeeding caused a marked increase in BrdU labeling in hepatocytes within and surrounding AHF during the first week or two, most notably in animals not receiving PB during the fasting period. Both the number and volume percentage of liver AHF returned to control values within~2 weeks of the refeeding regimen. Assays of nuclear DNA fragmentation with samples of whole liver indicated that a 'laddering' effect was most noticeable in livers of animals subjected to the fasting-refeeding regimen when phenobarbital was not present during the fasting period. Studies of the levels of mRNA of several genes in the total liver revealed that the expression of c-myc increased 3-to 9-fold during the fasting periods but rapidly returned to normal *Abbreviations: AB, apoptotic body; AHF, altered hepatic foci; BrdU, bromodeoxyuridine; DAB, diaminobenzidine; DEN, diethylnitrosamine; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GST-P, glutathione Stransferase-π; H&E, hematoxylin and eosin; ; IGF, insulin-like growth factor; LI, labeling index; NEL, nick end labeling; PB, phenobarbital; PH, partial hepatectomy; TdT, terminal deoxynucleotidyltransferase.© Oxford University Press 1417 levels after refeeding. Levels of albumin and insulin-like growth factor I mRNAs decreased significantly during the fasting period, but rapidly reappeared on refeeding. These results indicate that the extensive loss of AHF during the short-term fasting periods occurs even when the number a...

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“…Calculations from succinate-C02 ratio ( 14C02 from [ 1 ,4-14C]succinate: l4Co2 from [2,3-14C]succinate) or from acetate-C02 ratio (14C02 from [l-14C]acetate: I4CO2 from [2-14C]acetate) in the presence of glutamine predicts that glutamine molecules entering the tricarboxylic acid cycle have a low probability of remaining in the cycle for a complete turn (Mallet et al 1986b;Fleming & Kight, 1994 . Because the addition of 3-mercaptopicolinate, an inhibitor of PEPCK, has no effect on glutamine oxidation, PEPCK plus pyruvate kinase may play only a minor role in the second decarboxylation of glutamine-C and the generation of pyruvate and alanine (Hanson & Parsons, 1977;Watford et al 1979;Watford & Tatro, 1989;Watford, 1994). Similarly, the step catalysed by oxaloacetate decarboxylase probably does not make a significant contribution to the decarboxylation of glutamine.…”

Section: Sclection De Substrats Cnergktiques Dans Les Cellules Intestmentioning

confidence: 99%

Fuel selection in intestinal cells

et al. 1995

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Phosphoenolpyruvate Carboxykinase of Rat Small Intestine: Distribution and Regulation of Activity and mRNA Levels

Cited by 15 publications

References 28 publications

Diabetes‐induced changes in guanine‐nucleotide‐regulatory‐protein mRNA detected using synthetic oligonucleotide probes

Diabetes‐induced changes in guanine‐nucleotide‐regulatory‐protein mRNA detected using synthetic oligonucleotide probes

The effect of short-term fasting, phenobarbital and refeeding on apoptotic loss, cell replication and gene expression in rat liver during the promotion stage

Fuel selection in intestinal cells

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