title: Insulin receptor downregulation in isolated hepatocytes of river lamprey (Lampetra fluviatilis).
abstract: Insulin receptor downregulation in the isolated hepatocytes of lamprey (Lampetra fluviatilis) was studied at the ambient temperature for this species. Preincubation of hepatocytes with 10(-9)-10(-8) M unlabeled insulin decreased insulin binding capacity to 43, 37, and 34% at 4, 15, and 25 degrees, respectively. Preincubation of hepatocytes in the presence of 10(-10) M unlabeled insulin had no effect on the 125I-insulin binding. The maximal decrease in the 125I-insulin binding was reached after 10 min of preincubation and was then maintained at a constant level for 2 hr. Competitive binding assays demonstrated that preincubation with unlabeled insulin resulted in a 45% decline in the number of binding sites. In rat adipocytes and frog hepatocytes used for the comparison, preincubation with insulin caused a 65% decrease in cell-surface receptors, while intracellular (internalized receptors) increased proportionally. In contrast, in the lamprey hepatocytes both cell-surface and intracellular receptors decreased. We conclude that insulin receptors of the lamprey hepatocytes could be down-regulated at the ambient temperature for the species and at the physiological concentrations of insulin (10(-9)-10(-8) M).
authors.affiliation: Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Science, St. Petersburg, Russia.
authors.forename: B N
authors.initials: BN
authors.lastname: Leibush
authors.forename: Y L
authors.initials: YL
authors.lastname: Lappova
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D007457:Iodine Radioisotopes / Q000378:metabolism; D007798:Lampreys / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011895:Rana ridibunda; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000032:analysis / Q000378:metabolism*; D013696:Temperature
chemical_list: D007328:Insulin; D007457:Iodine Radioisotopes; D011972:Receptor, Insulin