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Pharmacological Study of Intracellular Second Messengers that Affect Active Ion Transport in the Midgut of Tobacco Hornworm, Manduca sexta
Author(s) -
LEE KyeongYeoll
Publication year - 2003
Publication title -
entomological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.421
H-Index - 20
eISSN - 1748-5967
pISSN - 1738-2297
DOI - 10.1111/j.1748-5967.2003.tb00061.x
Subject(s) - manduca sexta , midgut , biology , thapsigargin , protein kinase a , manduca , cyclic nucleotide , second messenger system , phosphatase , calcium , biochemistry , endoplasmic reticulum , intracellular , medicine , kinase , nucleotide , insect , phosphorylation , larva , botany , gene
Midgut active ion transport changes during the final larval stage of the tobacco hornworm. The short‐circuit current ( I sc ) of the posterior midguts dissected from feeding fifth instars (day 2) is higher than that of midguts from wandering larvae (day 5). The I sc of midguts from day 2 larvae is inhibited by 1 mM cAMP and 0.1 mM cGMP, whereas the midguts from day 5 larvae are stimulated by cAMP but unaffected by cGMP. A similar pattern is observed if the midguts are exposed to the cyclic nucleotide derivative, 8‐bromo‐cGMP. Exposure to the calcium ionophore, A23187, or the endoplasmic calcium ATPase inhibitor, thapsigargin, slightly inhibited the I sc of day 2 larval midguts, but this inhibition was not significant. Pharmacological agents known to modulate the activities of protein kinase A, protein kinase C, or protein phosphatases did not change the I sc . These results indicate that midgut active ion transport is modulated by cyclic nucleotides, but the manner of the response depends on the developmental status of the insect.