Rapid stimulation of intestinal D-glucose transport in teleosts by 17 alpha-methyltestosterone.
Effects of 17 alpha-methyltestosterone (MT) on transmural transport of 0.5 mM D-[3H]-glucose across upper intestine of the herbivorous teleost, Oreochromis mossambicus, were examined using modified Ussing chambers containing a physiological saline. Treatment tissues were preincubated with MT on the serosal surface for 30 min, while control tissues were incubated with an equivalent volume of 70% ethanol. Stimulation of mucosal-to-serosal D-glucose flux (Jm----s) by MT was dose dependent with maximal transport enhancement at 15 ng MT/ml saline (215% of control) and inhibition of sugar transfer occurring at 50 ng MT/ml (60% of control). Hormone treatment (15 ng MT/ml) significantly (P less than 0.05) increased net transmural D-glucose flux (Jnet; control = 0.36 +/- 0.084, MT = 0.75 +/- 0.130 nmol.cm-2.min-1) as a result of enhancing Jm----s (control = 0.52 +/- 0.048; MT = 0.91 +/- 0.078 nmol.cm-2.-1) without having a significant effect on the serosal-to-mucosal flux (Js----m). Mucosal addition of 1 mM phloridzin significantly (P less than 0.05) reduced glucose transport Jm----s in the presence and absence of MT, without altering the respective Js----m fluxes. Serosal addition of the hormone led to significant increases in Jm----s and Jnet in less than 20 min. This rapid intestinal response to MT was abolished by serosal addition of 1 mM colchicine, and therefore an increased insertion rate of performed glucose carriers is a suggested mechanism of hormone action.
Hazzard
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Department of Zoology, University of Hawaii, Manoa, Honolulu 96822.
Ahearn
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D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005399:Fishes; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000502:physiology*; D007422:Intestines / Q000502:physiology*; D007700:Kinetics; D008777:Methyltestosterone / Q000494:pharmacology*; D008954:Models, Biological; D009130:Muscle, Smooth / Q000502:physiology; D010695:Phlorhizin / Q000494:pharmacology
D010695:Phlorhizin; D005947:Glucose; D003078:Colchicine; D008777:Methyltestosterone