
Fig. 7. Representative effects of 1 mmoll-1 cAMP on K+ flux in the main segment of a Malpighian tubule of Drosophila melanogaster. Filled columns represent flux values prior to cAMP stimulation. Open columns represent flux values after the addition of cAMP. K+ flux rates were significantly increased by cAMP at sites 15 (open versus closed columns) but not at site 6. Similar patterns were seen for all other tubules studied. Values are means ± S.E.M., N=27 sites on five tubules (P>0.05).