Biomedical subjects

K Chiku

Publications and source records attributed to K Chiku.

7 recordsLinked to original sources

PubMed1997

Effect of varying amino acid levels on protein metabolism in nephrotic rats during total parenteral nutrition.

In an attempt to determine appropriate diet in nephrotic syndrome, nephrotic rats, induced by puromycin aminonucleoside, were nourished by total parenteral nutrition fluid containing the same energy, but three different levels (1.65, 3.3, and 6.6%) of amino acids for 7 d. The fractional rate of total protein synthesis in the liver was determined by injecting a flooding dose of [3H]phenylalanine. The proportion of newly synthesized proteins retained and exported by the liver was estimated by injecting a tracer dose of [14C]leucine and then measuring the protein radioactivity remaining in the liver and present in the plasma after secretion was completed. Nephrotic animals synthesized more protein than control animals. Although the absolute synthesis rates of total protein in liver were increased with increasing amino acid administration, the absolute rates of synthesis of albumin were higher in the 3.3% group than in the other groups in nephrotic rats. However, kidney protein synthesis in nephrotic rats was higher in the 1.65% group than in the 3.3% group. Interestingly, the 3.3% group revealed the smallest urinary excretion of total protein and albumin. In addition, in the 3.3% group, plasma concentrations of total protein and albumin were higher, and plasma concentrations of total cholesterol and triglyceride were lower than in other groups. It was concluded that the 3.3% group, corresponding to a normal protein diet, has the greatest salutary effect on urinary protein excretion, followed by protein and lipid metabolism, in nephrotic rats. Not only protein intake but also the energy:protein ratio are important for diet therapy in nephrotic animals. The technique of total parenteral nutrition may be useful in defining the factors involved in glomerular permeability or permselectivity and intracellular protein metabolism.

Amino Acids↗

PubMed1993

Amino acids suppress intracellular protein degradation in rat liver during parenteral nutrition.

The effects of variations in the amino acid supply on the rates of synthesis and degradation of liver proteins and on the rate of synthesis and secretion of plasma proteins were investigated. Rats were nourished by infusion of total parenteral nutrition solutions containing four different levels (0, 1.65, 3.3 and 6.6%) of amino acids for 7 d. The fractional rate of total protein synthesis in the liver was determined by injecting a flooding dose of [3H]phenylalanine. The proportion of newly synthesized proteins retained and exported by the liver was estimated by injecting a tracer dose of [14C]leucine and then measuring the protein radioactivity remaining in the liver and present in the plasma after secretion was completed. The rate of plasma albumin synthesis was significantly lower in the 0 and 1.65% amino acid groups than in the other groups. The fractional synthesis rates of liver domestic proteins, however, were essentially the same in rats administered all levels of amino acids except for the 0% amino acid group, which showed a slightly higher value than the other groups. The fractional degradation rates of liver domestic proteins, calculated as the difference between the fractional synthesis rate of liver domestic proteins and the net gain of liver proteins, were found to be inversely related (r = -0.999, P < 0.05) to the level of amino acids in infusion solutions up to 3.3% amino acids. It was concluded that protein degradation plays the predominant role in the regulation of liver protein mass.

Amino Acids↗

PubMed1992

ECG changes under hyperkalemia with nephrectomy in the rat.

Electrolyte abnormalities have become an increasingly important cause of arrhythmias. Although the electrocardiographic (ECG) changes under hyperkalemia in the rat are poorly understood, it is conceivable that excess plasma potassium may also alter the cardiac excitations in the rat. Further, effects of hyperkalemia on ECG in the rat may differ from other species that have ST-segment and longer QT intervals in ECG. The present study was designed to determine the diagnostic criteria for ECG manifestations to various levels of plasma potassium concentration. For this purpose, hyperkalemia was induced by nephrectomy with and without infusions. Because it was difficult to produce various levels of plasma potassium concentration by only nephrectomy, we used two kinds of infusions to obtain especially moderate levels of nephrectomy-induced hyperkalemia. ECGs were recorded 24, 36, and 48 hours after nephrectomy. Plasma potassium concentration and number of abnormal ECGs were increased time-dependently. Increased T wave amplitude was present with mild hyperkalemia. The typical T wave change observed with so-called sinoventricular conduction levels of potassium concentration in species with long QT intervals did not occur in the rat. PR interval and QRS duration became slightly shorter within moderate hyperkalemia. P wave disappeared in most rats at potassium levels above 8.0 mEq/l. In advanced hyperkalemia (plasma potassium concentration above 7.5 mEq/l), conduction in all parts of the heart was suppressed. Moreover, sinoventricular conduction appeared. Thus, the diagnostic criteria for ECG manifestations to various levels of plasma potassium concentration in the rat were demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Effect of enrichment of infusion solutions with branched chain amino acids in parenteral nutrition of rats.

The effect of enrichment of the branched chain amino acids (BCAAs) leucine, isoleucine and valine on total parenteral nutrition was studied in rats. Experimental infusion solutions with a sufficient, marginal or deficient level of glucose contained either the conventional amino acid composition (22.6% BCAAs) or a BCAA-enriched amino acid composition (36% BCAAs). Rats were infused with experimental solutions for 4 days and several parameters of protein metabolism were evaluated in various tissues. Under conditions of sufficient energy supply, BCAA-enriched and conventional groups showed similar body weight gains and muscle protein degradations as measured by urinary 3-methylhistidine excretion. Polysome profiles in the liver and gastrocnemius muscle of the BCAA-enriched group were more heavily aggregated than those of the conventional group. Under the conditions of marginal or deficient energy supply, beneficial effects of BCAA enrichment over the conventional amino acid composition became more evident in terms of better body weight retention, higher RNA/DNA ratio and heavier polysome profile in both liver and muscle, and reduced protein catabolism in muscle. The present study suggests that enrichment of BCAAs, particularly valine and isoleucine, may be useful for nutritional support under hypercatabolic or stressed conditions.

Amino Acids, Branched-Chain↗

PubMed1986

Effects of glucose and amino acid depletions on protein synthetic parameters in liver and skeletal muscle of rats during parenteral nutrition.

Rats were nourished by intravenous infusion of four different experimental solutions: total parenteral nutrition (TPN) solution (group I); glucose-depleted TPN solution (group II); amino acid-depleted TPN solution (group III); and glucose- and amino acid-depleted TPN solution (group IV). All except group I animals lost body weight and showed negative nitrogen balance during a 7-day experimental period; glucose-depleted groups II and IV generally suffered more severely than amino acid-depleted group III. However, the concentration of plasma albumin in group III was significantly lower than that in the other groups. The weights of liver and gastrocnemius muscles after 7 days of infusion with different nutrient compositions were fairly well correlated with the RNA/DNA ratios in these tissues. Infusion of nutritionally deficient solutions caused progressive disaggregation of polysomes in both liver and gastrocnemius muscles, indicating variable degrees of impairment of protein synthesis in these tissues. The changes in polysomal profiles were rapid and sensitive; the polysomal disaggregation was evident within one day of infusion with deficient solutions. The determination of polysomal profiles in various tissues may be useful in optimizing the composition of TPN solutions.

Amino Acids↗

PubMed1983

Influence of chronic renal failure on protein synthesis in rat liver and muscle.

Protein-synthetic activity in the liver and muscle of rats with chronic renal failure (CRF) of 2 weeks' duration was studied by examining RNA/DNA ratios and polysome profiles and in vitro protein synthetic activity of isolated polysomes. CRF was found to cause differential effects on protein synthesis in the liver and muscle. In the liver, CRF caused impairment of protein synthesis only in the fed condition; CRF rats maintained the same "basal" protein synthetic activity as the sham-operated control rats upon 18 hours' starvation. In the muscle, the effect of CRF was manifested only in the starved condition; CRF caused extensive disaggregation of polysomes when animals were starved. It is proposed that the muscle serves as a "reserve" protein when animals sustain a protein-catabolic state such as CRF.

Animals↗

PubMed1981

Cell-free synthesis of ornithine aminotransferase of rat liver.

Mitochondrial ornithine aminotransferase was synthesized in a rabbit reticulocyte cell-free system using polysomal mRNA from rat liver. Upon analyzing the primary translation product by electrophoresis and fluorography, we found that ornithine aminotransferase is synthesized not as a large precursor but as one with its authentic size. Free ribosomes were found to be the main site of synthesis of ornithine aminotransferase.

Animals↗