EFFECT OF INHIBITORS ON ACTIVE TRANSPORT BY TURTLE INTESTINAL SEGMENTS

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Abstract
Everted intestinal segments of the painted turtle Chrysemys picta were incubated in the presence of metabolic inhibitors and under nitrogen. Uptake and accumulation of D-glucose (4.5 mg/100 ml) were measured after incubation of the segments for one hour at 30[degree] C. Results show that phlorizin, iodoacetate and ouabain were potent inhibitors of glucose absorption, while 2,4-dinitrophenol, malonate and cyanide and azide were less effective. Nitrogen gas (replacing aeration) caused no significant inhibition of glucose absorption in these preparations. When intestinal segments in an environment of nitrogen were exposed to a 1 x 10-6 concentration of iodoacetate, mucosal uptake of glucose was completely blocked, This result was in contrast to the absence of any inhibitory effect of the same concentration of IAA under aerobic conditions. The concept of turtle metabolism which emerges is one of flexibility and tolerance to conditions in which oxygen is in short supply. The turtle may use oxidative pathways for cellular respiration but appears to be capable of utilizing glycolysis as the source of ATP for active transport when the aerobic path is blocKed. The natural habits of this animal and its low metabolic rate make this possible.

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