Acute ethanol dosage reduces the synthesis of smooth muscle contractile proteins in the small intestine of the rat.

Preedy, Victor R.; Duane, P.

doi:10.1136/gut.29.9.1244

Cited by 23 publications

(10 citation statements)

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“…There is evidence of wasting of lean body mass in alcoholic liver disease (ALD), especially of skeletal muscle [7], but little is known about the involvement of the gut in the wasting process. Studies in rats have provided evidence of depressed small-intestinal mucosal protein synthesis [8][9][10] in response to alcohol, suggesting the existence of similar deficits in humans. Furthermore, little is known about the functional correlates of possible gastrointestinal involvement in humans in response to chronic ethanol ingestion.…”

Section: Introductionmentioning

confidence: 99%

Small-intestinal mucosal protein synthesis and whole-body protein turnover in alcoholic liver disease

et al. 1999

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We used stable-isotope-labelled amino acids to measure the effects of alcoholic liver disease (ALD) on whole-body protein turnover and small-intestinal mucosal protein synthesis. Groups comprising eight patients with ALD and eight healthy control subjects were studied. They received primed, continuous intravenous infusions of L-[1-(13)C]leucine after an overnight fast; after 4 h, duodenal biopsies were obtained via endoscopy. Protein synthesis was calculated from protein labelling relative to intracellular leucine enrichment. Rates of duodenal mucosal protein synthesis were 2. 58+/-0.32%.h(-1) (mean+/-S.D.) in the normal subjects and 2.04+/-0. 18%.h(-1) in the ALD patients (P<0.003), despite the fact that the protein synthetic capacity (microgram of RNA/mg of protein) was higher in ALD patients (160+/-14 compared with 137+/-6 microgram/mg; P<0.003). The mucosal cell size (protein/DNA ratio) was lower in ALD patients (9.23+/-0.91 compared with 13+/-2.2 microgram/mg; P<0.002). Although the mean rates of whole-body protein turnover were not significantly different between the two groups (204+/-18 and 196+/-44 micromol leucine.h(-1).kg(-1) for ALD and control subjects respectively), there was, in the ALD patients, an inverse relationship between the rate of small-intestinal mucosal protein synthesis and the severity of ALD; furthermore, there was a direct relationship between the rate of whole-body protein turnover and the severity of ALD. Thus there was an inverse relationship between the rate of small-intestinal mucosal protein synthesis and the rate of whole-body protein turnover in ALD patients, which was not seen in the normal subjects.

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Section: Introductionmentioning

confidence: 99%

Small-intestinal mucosal protein synthesis and whole-body protein turnover in alcoholic liver disease

et al. 1999

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“…Synthesis rates in subcellular protein fractions of intestinal smooth muscle in the entire regions of the gastrointestinal tract have never previously been investigated. The studies by Preedy et al (1988) and Preedy & Peters (1990) only investigated synthesis rates pertaining to protein subfractions of the entire small intestinal mass. Intestinal smooth muscle contractile protein synthesis has been measured by Millward et al (1980) in unspecified regions.…”

Section: Discussionmentioning

confidence: 99%

“…The study by Preedy, Duane & Peters (1988) showed that intestinal contractile protein synthesis in vivo was relatively sensitive to acute ethanol dosage. Fractional synthesis rates of con-tractile proteins were reduced by 40-50% (p Ͻ 0.001), compared with an approximate 20% decline in the synthesis of mixed intestinal proteins.…”

Section: Introductionmentioning

confidence: 99%

“…Fractional synthesis rates of con-tractile proteins were reduced by 40-50% (p Ͻ 0.001), compared with an approximate 20% decline in the synthesis of mixed intestinal proteins. However, in the study of Preedy et al (1988) measurements were made on contractile proteins contained in the whole small intestine (with the mucosal layer intact). As approximately 40% of contractile proteins also reside in the mucosal layer, then changes in synthesis rates of the mucosal layer could mask changes occurring in the longitudinal and circular muscle layers that are important for gastrointestinal peristaltic action and motility.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of contractile and non‐contractile protein synthesis in the stomach, small and large intestine and caecum of the rat, and response to acute ethanol dosage

1996

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An investigation was made into the relative composition and synthesis rates of smooth muscle contractile proteins in vivo in different regions of the rat gastrointestinal tract. There was considerable homogeneity in the composition of sarcoplasmic proteins in the small bowel (i.e. 54-58 mg/g) but considerable variability in the large bowel, i.e. highest in the caecum (97 mg/g) and lowest in the colon (21 mg/g). The myofibrillary protein concentration was constant throughout the gastrointestinal tract, i.e. 20-34 mg/g. Stromal fractions varied from 6 to 39 mg/g and was highest in the cardiac region of the stomach and lowest in the duodenum. Fractional rates of protein synthesis were measured with a flooding dose of L-[4-(3)H]phenylalanine. In control rats synthesis rates in sarcoplasmic protein fractions were relatively much higher (43-107%/day) than myofibrillar (27-52%/day) or stromal (6-26%/day) proteins. Fractional rates of stromal protein synthesis showed the greatest variability while myofibrillar synthesis rates the least, throughout the alimentary tract. Jejunal seromuscular layer myofibrillar proteins had the highest synthesis rates (49%/day). In response to acute ethanol injection, protein synthesis in all jejunal fractions fell by 20-30%. Contractile and non-contractile proteins from the cardiac region of the stomach, duodenal seromuscular layer and large bowel seromuscular layer were insensitive to ethanol administration. Protein synthesis of sarcoplasmic proteins from the antrum, ileum seromuscular layer and myofibrillar proteins from the ileum seromuscular layer and caecum were also significantly depressed as a result of ethanol treatment.

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“…The pellet was the 'stromal' protein fraction. 9 The terminology 'cytoplasmic' 'contractile' and 'stromal' was defined in detail in our previous paper.9 Briefly, the cytoplasmic fraction contains principally soluble enzyme proteins; the 'contractile' fraction contains proteins such as actin and myosin and other myofibrillar proteins; the 'stromal' fraction comprises of connective tissue proteins such as collagen, and possibly traces of unextractable contractile protein.…”

Section: Separation Of Protein Compartmentsmentioning

confidence: 99%

Protein synthesis of muscle fractions from the small intestine in alcohol fed rats.

Preedy

1990

Gut

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The effects of chronic ethanol feeding on the amounts and synthesis rates of cytoplasmic, contractile, and stromal protein fractions were investigated in the small intestine of eight pairs of immature and seven pairs of mature rats. Treated rats were fed ethanol as 36% of total energy in a nutritionally adequate liquid diet. Paired controls were fed isovolumetric amounts of the same diet in which ethanol was substituted by isocaloric glucose. After six weeks the total cytoplasmic and contractile protein content in immature rats was reduced by 18% and 31%, respectively (p-.0007). The decline in the stromal protein content (26%) was not statistically significant (p=0-130). In mature rats the protein contents were also reduced in the cytoplasmic (25%, p=0035) and contractile (27%, p=0005) protein fractions, though the stromal protein fraction was unaltered (p=0913). In immature rats fractional rates of protein synthesis in cytoplasmic and contractile protein fractions of the small intestine were unaltered by chronic ethanol feeding (p-0.853). In mature rats, the synthesis rates of corresponding fractions declined, by 18% and 31%, respectively, but were also not statistically significant (pS0.369). Absolute rates of protein synthesis in immature rats fell by 6% (p=0549) in the cytoplasmic and 31% in the contractile protein fraction (p=0045). In mature rats, the corresponding reductions were 38% (p=0106) and 48% (p= 0.033), respectively. Virtually no radioactivity could be detected in the stromal fraction, signifying very low synthesis rates. Chronic ethanol feeding reduces the amount of protein in the small intestine of the immature and mature rat with the contractile protein fraction showing the greatest decrease. In the absence of statistically significant reductions in fractional synthesis rates a partial adaptation in turnover rates may have occurred.

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Acute ethanol dosage reduces the synthesis of smooth muscle contractile proteins in the small intestine of the rat.

Cited by 23 publications

References 11 publications

Small-intestinal mucosal protein synthesis and whole-body protein turnover in alcoholic liver disease

Small-intestinal mucosal protein synthesis and whole-body protein turnover in alcoholic liver disease

Characterization of contractile and non‐contractile protein synthesis in the stomach, small and large intestine and caecum of the rat, and response to acute ethanol dosage

Protein synthesis of muscle fractions from the small intestine in alcohol fed rats.

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