Patricia B. Swan

Copper-Zinc and Manganese Superoxide Dismutase Activities in Cardiac and Skeletal Muscles during Aging in Male Rats

The activities of total superoxide dismutase (SOD) and the manganese (Mn SOD) and copper-zinc (Cu-Zn SOD) forms were determined in the supernatant fraction of heart, liver and six skeletal muscles from rats during aging. Total SOD activity increased in most muscles between 3 and 23 months of age. There was no change in activity in liver between 3 and 19 months of age. The increase in total activity in heart was due to increased Mn SOD activity, whereas increases in skeletal muscles were due to Cu-Zn SOD or to both Cu-Zn and Mn SOD. The nutritional implications during aging are discussed.

In vitro amino acid incorporation by the post-mitochondrial supernatant from rat liver

Abstract Interest in the use of the post-mitochondrial supernatant (PM-supernatant) for the study of in vitro amino acid incorporation arose from experiments indicating that the ribosomal aggregation of the PM-supernatant system more nearly represented that of the intact cell than did other ribosomal preparations. The PM-supernatant system was found to be 25 or 50 % more active than the microsomal and ribosomal amino acid incorporation systems. For PM-supernatant in vitro incorporation of l -[ 14 C]valine into acid insoluble material, ATP, GTP, an energy generating system, Mg 2+ , K + , and a mixture of l -amino acids were necessary. Sephadex G-25 column chromatography of the PM-supernatant, pH 7.4, and presence of glutathione during homogenization of the tissue were necessary for optimal PM-supernatant in vitro incorporation. Under these conditions the rate of l -valine incorporation by the PM-supernatant from 0.17 to 0.20 nmoles/min per mg RNA for a liver from a fed rat. Fasting (20 h) prior to sacrifice, resulted in a 30–40 % decrease in amino acid incorporation by the PM-supernatant as well as a decrease in ribosomal aggregation. The decrease in PM-supernatant incorporation by fasting was found to be associated with both polysomal and cell sap factors.

Effect of starvation and refeeding on catalase and superoxide dismutase activities in skeletal and cardiac muscles from 12-month-old rats

Catalase and superoxide dismutase (SOD) activities were determined in muscles from 12-month-old rats after severe starvation and after subsequent refeeding. Catalase increased in most muscles after starvation and decreased after refeeding, while SOD remained unchanged.

Evidence for increased peroxidative activity in muscles from streptozotocin-diabetic rats

Abstract The ability of cardiac and skeletal muscles from diabetic rats to metabolize superoxide and hydrogen peroxide was determined by the activities of superoxide dismutase (SOD) and catalase, respectively. Male and female Sprague-Dawley rats, 43 days old, were made diabetic with a single intravenous injection of streptozotocin (70 mg/kg body weight). On the 80th day after injection the blood glucose concentration of these rats was increased fourfold, and the plasma insulin concentration was decreased four- to fivefold compared to controls. Body weights of male diabetic rats were 6 1% and those of female diabetic rats were 66% of their ad libitum-fed controls. The seven different skeletal muscles examined weighed less in the diabetic rats than in controls of the same age and body weight. The hearts of the diabetic rats weighed more than those of controls of the same age and body weight. Comparison to the body weight controls allowed the distinction of specific effects due to lack of insulin from effects due to retardation in muscle growth. Increased catalase activity in all muscles examined from diabetic rats (plantaris, gastrocnemius, and heart) suggested a response in catalase activity similar to that of starved rats. SOD activity was not altered in the diabetic rat skeletal muscles and erythrocytes, but was somewhat decreased in the heart.

The effect of three hypolipidemic drugs on catalase activity and peroxisomal and mitochondrial palmitate oxidation in rat cardiac and skeletal muscle

Catalase activity and peroxisomal and mitochondrial palmitate oxidation have been investigated in cardiac and skeletal muscle from rats fed clofibrate, ciprofibrate or nafenopin in an unrefined diet for different periods of time. Nafenopin was also added to either a high carbohydrate (70% of kilocalories from glucose) or high fat (70% of kilocalories from lard) diet and fed to rats for either 1 or 3 weeks. Catalase activity was elevated in all muscles from rats fed the hypolipidemic drugs. The response of catalase activity in muscle to clofibrate was dose-dependent. The response time of catalase activity was different in individual muscles. Peroxisomal palmitate oxidation was elevated in the heart and soleus muscle from rats fed nafenopin in either the high-carbohydrate or the high-fat diet. There was no change in peroxisomal palmitate oxidation in psoas or extensor digitorum longus muscle from rats fed the drugs. Mitochondrial palmitate oxidation was only slightly increased by nafenopin in the heart and soleus muscles after 3 weeks of nafenopin feeding. The results suggest that the cardiac muscle, like the liver, responds to hypolipidemic drug treatment with an increase in peroxisomal fat oxidation. The skeletal muscle response is less specific and that tissue may not contribute to the hypolipidemic effect of the drugs. The findings also suggest that these drugs do not induce peroxisome proliferation in skeletal muscle.

The effect of acute dietary restriction on muscle fibre number in weanling rats

1. Male Sprague-Dawley rats were allocated at 100 g into either an ad lib.-fed control group or a food-restricted group. The restricted group was fed for 9 d at 25% of ad lib. intake. Controls were killed at a body-weight of 100 g and 29 d of age. 2. The effects of food restriction on muscle weight, fibre number, fibre diameter, DNA, and protein were examined in three skeletal muscles, the soleus, plantaris and extensor digitorum longus (EDL). 3. Acute dietary restriction caused body- and muscle-weight loss and a decrease in both the number and cross-sectional area of muscle fibres in each of the muscles. 4. The restriction halted growth-related increases in DNA in all muscles and decreased the protein:DNA value in the plantaris and EDL. 5. These results indicate that present theories describing cellular development are not adequate to define growth potential or growth retardation of skeletal muscle.

Anomalies in polysome profiles caused by contamination of the gradients with Cu2+ or Zn2+

The presence of 30 μM Cu2+ or Zn2+ in sucrose gradients used to determine the extent of ribosome aggregation in rat liver preparations resulted in profiles which were abnormally aggregated. This problem was eliminated by inclusion of EDTA in the gradient or by the use of detergents other than deoxycholate.

The dynamic nature of zinc availability from foods in vivo. Implications for in vitro methods.

This paper presents a review of data from animal experiments demonstrating that the relative availability of zinc from foods is affected by an interaction between the source and amount of zinc consumed. Zinc availability from foods was determined by whole body counting after feeding65Zn-labeled meals containing varying amounts of zinc. Relative to availability from zinc chloride, zinc availability from foods such as chicken, milk, and peanut butter was greater when determined using 98 rather than 16 Μg zinc in the meal. In rats fed the higher dose of zinc, there were greater differences in zinc availability among the 15 foods studied, and zinc availability was greater from some foods than from zinc chloride. After an in vitro enzymatic digestion, neither zinc solubility nor the partitioning of zinc between low and high molecular weight substances was useful for predicting zinc availability in vivo. These data indicate that zinc availability from food is not a constant proportion of availability from a zinc salt. In view of the dynamic nature of zinc availability in vivo, the inability to accurately simulate different physiological responses to varying quantities of certain foods may limit the usefulness of in vitro methods.

Degradation of 5-hydroxylysine in the rat and in the perfused liver

Abstract The fate of the four stereoisomers of 5-hydroxylysine has been determined by metabolic studies of the 6- 14 C-labeled racemates and d -isomers. Both l -isomers were rapidly degraded to 14 CO 2 via glutaryl-CoA in the intact rat and in isolated perfused liver. Approximately 10%, of the 14 C from hydroxy- d -lysine-6- 14 C and 1% from allohydroxy- d -lysine-6- 14 C was expired as 14 CO 2 in the intact animal. Neither d -isomer was taken up by the perfused liver. Hydroxy- d -lysine was excreted largely unchanged, together with small amounts of 5-hydroxypipecolate tentatively identified as the d -isomer. The 14 C from allo -hydroxy- d -lysine was excreted largely as 5-hydroxypipecolate, presumably the l -isomer. The urine contained no detectable allo -5-hydroxypipecolate. The urinary hydroxypipecolate derived from both hydroxy- and allohydroxy- d -lysine was taken up but not metabolized by perfused liver. 2-Amino-5-hydroxyadipate- 14 C was metabolized to a limited extent by the rat or perfused liver and did not label 2-ketoadipate or glutarate in overloading experiments. No evidence was found for the participation of hydroxypipecolate or 2-amino-5-hydroxyadipate in the metabolism of the l -isomers of hydroxylysine.

Effect of dietary zinc on 65-ZN absorption and turnover in rats

Abstract The effect of zinc intake on retention, absorption, and biological half-life of 65-Zn was investigated using whole body counting after the carrier-free radioisotope was administered intragastrically or intramuscularly to 7-week old male rats. When animals consumed 7.8, 11.7, 16.0, 20.8, 36.8, 80.2, or 149.1 mg Zn/kg diet for 3 weeks before and 4 weeks after 65-Zn administration, the biological half-life and the retention of gavaged or injected 65-Zn were curvilinearly related to the dietary zinc concentration. Absorption was similarly affected, except that absorption was nearly 100 per cent at the two lowest levels of intake. Zinc concentrations in bone and serum were unaffected except in animals fed 7.8 mg Zn/kg diet. When zinc intakes varied only 4 days before 65-Zn administration, retention of injected 65-Zn and absorption were less affected. Animals fed 11.5 rather than 85.0 mg Zn/kg beginning 7 to 8 hours after 65-Zn administration, had greater retention of gavaged or injected 65-Zn; absorption and biological half-life of 65-Zn were also greater. Thus, retention of dietary zinc by the body depended on recent and subsequent zinc intake, with recent intake affecting mainly absorption, and subsequent intake affecting mainly excretion. Adjustments in absorption and excretion occurred within days, and were highly coordinated when zinc intakes exceeded the requirement.