家蚕変態期の中腸における酸性フォスファタ-ゼおよび核酸分解酵素の活性

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Histochemical and biochemical studies on the two hydrolases, acid phosphatase and acid nuclease were carried out in the midgut of the silkworm, Bombyx mori during metamorphosis. Light microscopic observation revealed that the acid phosphatase in the midgut epithelium began to appear from the late days of last larval instar, then showed very high activity at the spinning time. After larval-pupal ecdysis this enzyme could hardly be seen in the newly formed pupal midgut until the 7th day of the pupa. Toward the adult development, however, acid phosphatase reappeared in the tissue, showing the highest activity at the time of pupal-adult transformation. Developmental changes of the acid phosphatase activity during the metamorphosis were almost coincident with the occurrences of lysosomes and cytolysomes in the degenerated midgut cells. Throughout the pupal stage, incessant high enzyme activity was maintained in the lumen which was mainly composed of degenerated larval epithelium. Biochemical results for activities of acid-DNase and RNase, were also consistent with those of histochemical observation. On the basis of above results, it is suggested that the midgut of silkworm during metamorphosis undergoes a gradual degradation under the presence of hydrolases like acid phosphatase and nuclease which are originated from lysosomes in the degenerated cells.
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