Some Biochemical Features of White Muscle Disease in Lambs, and the Influence of Selenium

Abstract

Typical white muscle disease has been induced in lambs that were normal at weaning but thereafter fed natural dystrophogenic fodder for 2-4 months. Protection from the disease was given by selenium when it was administered regularly as an oral drench, or incorporated into an intraruminal heavy pellet placed in the rumen at weaning.Calcium and magnesium levels in serum were unaffected by the dystrophic condition, although urinary excretion of both ions was decreased. This lowered urinary excretion was associated with high levels of calcium in both heart and skeletal muscle, and to some extent associated with raised levels of calcium and magnesium in washed mitochondria isolated from the same tissues.The respiratory properties of the mitochondria were examined polarographically. No differences were found between heart muscle mitochondria isolated from normal and dystrophic hearts. Skeletal muscle mitochondria from dystrophic animals showed lowered respiratory rates with palmitoyl-DL-carnitine and acetyl-DL-carnitine as substrates. The smaller differences with pyruvate and succinate were not significant. Respiratory control ratios for the dystrophic skeletal muscle organelles were always 1 . 0, but for selenium-supplemented animals were always > 1 ·0.To some extent at least the abnormalities appear to be associated with the high levels of calcium in the tissues and mitochondria of dystrophic lambs.

Retention of 45Ca in Rats and Lambs Associated with the Onset of Nutritional Muscular Dystrophy

“…There was little evidence of 45Ca retention in heart muscle and it may be significant that in our earlier study (Godwin et al 1974) no abnormalities occurred in heart muscle mitochondrial respiratory activity even at a time when white muscle disease was well advanced. Kidney damage has been recognized as a feature of the pathology of selenium deficiency in rats (Schwarz 1961), and the autoradiographs of the kidney show that 45Ca retention is an early feature of the subsequent tubular damage.…”

“…They lend further support for the essential similarity of the hereditary and nutritional types of muscular dystrophy (Godwin 1972;Godwin et al 1974). They show that the earliest abnormality during the onset of selenium deficiency may be with respect to an ion, the redistribution of which would be expected to cause profound changes in muscle integrity ..…”

“…In the second experiment normal Merino lambs were weaned onto dystrophogenic hay in the manner described elsewhere (Godwin 1972;Godwin et al 1974). Some were given no selenium supplement and were allowed to develop white muscle disease, others were supplied with a selenium supplement either as an oral drench or as an intraruminal heavy pellet (Godwin et al 1974). A third but smaller,group was given a selenium supplement after developing white muscle disease and was designated the recovery group (Kuchel and Godwin, unpublished data).…”

“…Animals were killed at 0, 1, 2, 3, 4, 5, 6, 8; and 10 weeks after being introduced to the diets. In the second experiment normal Merino lambs were weaned onto dystrophogenic hay in the manner described elsewhere (Godwin 1972;Godwin et al 1974). Some were given no selenium supplement and were allowed to develop white muscle disease, others were supplied with a selenium supplement either as an oral drench or as an intraruminal heavy pellet (Godwin et al 1974).…”

“…Work published recently from this laboratory (Godwin et al 1974) showed that calcium retention occurred early in the development of experimental white muscle disease. Associated with this calcium retention was a reduction in respiratory rate of mitochondria isolated from dystrophic muscle when incubated in the presence of certain substrates.…”