Rapid stimulation of intestinal D-glucose transport in teleosts by 17 alpha-methyltestosterone

Abstract

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.