Oxidation-reduction potentials of the midgut tissues of larvae of the silkworm, Bombyx mori L.

Abstract

The oxidation-reduction potentials of the homogenate of larval midgut tissue were measured with the use of the potential-time-curve method.
1. In the three divisions (anterior, middle, and posterior) of the midgut tissue of 5th instar larvae, the potentials drop speed (PDS) was highest in the posterior midgut and lowest in the anterior one, while there was hardly any difference in the final potential (FP) among them.
2. The PDS of the midgut tissue from the larvae which had undergone 2 days' starvation after the 4th ecdysis was considerably lower than that of the fed larvae. But the FP level of the midgut tissue of starved larvae was the same as that of fed larvae.
3. Throughout the feeding period of the 5th instar, the FP's and PDS's of the midgut tissue were maintained at a more or less constant levels. On the other hand, in the molting stage the FP's dropped to the level of about -500mV in the early 4th molting, but in other sample, they were retained at the same leve (-200mV) as those in the feeding period. The PDS was poor just before molting, and increased to maximum in the late molting, but fell off just before ecdysis.
4. The PD's of the blood were considerably lower than those of the midgut tissue, but the changes of the former in course of the larval development were found to be propotional to those of the latter. While the FP's of the former were roughly in agreement with those of the latter.