Abstract
The fat body protein content of silkworms increased with 0.5 μg of thyroxine (T4) per gram of body weight and more so with 1 μg/g on days 4 and 8 after injection. Thyroxine with 1 μg/g dose, however, caused an earlier increase in protein content on day 2. The higher doses of T4 (2 and 5 μg/g) decreased the protein content. All T4 treated groups (except with an ineffective dose of 0.25 μg/g) showed reduced protein level in the adult stage in comparison to the control. Thyroxine with a dose of 0.25, 0.5 and 1 μg/g increased the fat body RNA content over the control level which was observed on days 2, 4 and 8. But on day 13, the RNA content in these groups returned to the control level. Higher doses of T4 (2 and 5 μg/g) decreased the RNA content during the developmental period. DNA content was not altered by lower doses of T4 (0.25,0.5 and 1 μg/g), while the higher doses (2 and 5 μg/g) surprisingly caused a reduction in DNA content during the larval, pupal and adult stages.
The increase in protein and RNA contents with lower doses of T4 and decrease with higher doses, indicates a biphasic nature of thyroid hormone action in silkworm fat body.
Résumé
La teneur en protéine de la matière grasse des vers à soie a augmente sous l’effect de 0.5 μg de thyroxine (T4) par gramme de poids corporel, l’augmentation étant m-e plus marquée sous l’effect de 1 μg/g 4 et 8 jours apres l’injection. Néammoins, 1 μg/g de thyroxine occasionnait deja une augmentation dès le 2 ème jour. Tous les groupes traités à la thyroxine (sauf dans le cas d’une dose de 0.25 μg/g sans effect) ont montré un niveau réduit de protéine au stade ádulte par rapport au cas témoin.
Une dose de 0.25 et 1 μg/g de thyroxine a augmenté la teneur en RNA de la matière grasse par rapport au niveau témoin observé les 2 ème, 4 ème et 8 ème jour. Mais au 13 ème jour, la teneur en RNA de ces groupes a rejoint le niveau témoin. Au cours de la période de croissance, les doses élevées de T4 (2 et 5 μg/g) ont réduit la teneur en RNA. La teneur en DNA ne fut pas modifiée par les petites doses de T4 (0,25; 0,5 et 1 μg/g) tandis que les doses plus élevées (2 et 5 μg/g) ont, d’une façon surprenante, provoqué une réduction de la teneur en DNA au couré des périodes larvaire, nymphal et adulte.
L’augmentation de la teneur en protéine et en RNA sous l’effet de petites doses de T4 et la diminution sous l’effect de doses élevées suggèrent une nature à deux phases de l’action de l’hormone thyroxidien dans la matière grasse du vers à soie.
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Chaudhuri, A., Medda, A.K. Thyroxine-Induced Alterations in Protein and Nucleic Acid Contents of Fat Body of Female Silkworms During Different Developmental Stages. Int J Trop Insect Sci 8, 43–48 (1987). https://doi.org/10.1017/S1742758400006937
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DOI: https://doi.org/10.1017/S1742758400006937