Glucose uptake via SGLT-1 is stimulated by beta(2)-adrenoceptors in the ruminal epithelium of sheep.
Glucose absorption via the sodium glucose-linked transporter (SGLT)-1, decreases the glucose concentration in the ruminant forestomach and may ameliorate or prevent ruminal lactic acidosis. Because acidotic ruminants show increased sympathetic activity, the possibility of adrenergic modulation of SGLT-1 was investigated. Glucose uptake into ovine ruminal epithelia was measured in Ussing chambers after the addition of 200 micromol/L (14)C-labeled glucose to the mucosal solution. Glucose uptake decreased (P < 0.05) by >50% in comparison with control after mucosal addition of the SGLT-1 inhibitor, phlorizin (100 micromol/L). Serosal preincubation with 100 micromol/L epinephrine increased (P < 0.05) the phlorizin-sensitive glucose uptake in the absence and presence of indomethacin (10 micromol/L). The effect of epinephrine was simulated by beta- (100 micromol/L isoproterenol) and beta(2)-receptor agonists (10 micromol/L terbutaline), as well as by direct stimulation of adenylyl cyclase (10 micromol/L forskolin). The serosal addition of methoxamine, clonidine, dobutamine or BRL 37344 had no effect. Inhibition of protein kinase A with 2 micromol/L H 89 completely abolished the stimulation of glucose uptake by epinephrine. We conclude that ruminal SGLT-1 can be stimulated via beta(2)-dependent generation of cyclic adenosine monophosphate.
Aschenbach
Jörg R
JR
Department of Veterinary Physiology, Leipzig University, D-04103 Leipzig, Germany. aschenb@rz.uni-leipzig.de
Borau
Titus
T
Gäbel
Gotthold
G
D000140:Acidosis, Lactic / Q000517:prevention & control / Q000662:veterinary; D058672:Adrenergic beta-2 Receptor Antagonists; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002247:Carbon Isotopes; D004837:Epinephrine / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010695:Phlorhizin / Q000494:pharmacology; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology*; D012417:Rumen / Q000378:metabolism*; D012756:Sheep; D012757:Sheep Diseases / Q000517:prevention & control; D051269:Sodium-Glucose Transporter 1
D058672:Adrenergic beta-2 Receptor Antagonists; D002247:Carbon Isotopes; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D018343:Receptors, Adrenergic, beta-2; D051269:Sodium-Glucose Transporter 1; D010695:Phlorhizin; D005947:Glucose; D004837:Epinephrine