Effects of metformin on tyrosine kinase activity, glucose transport, and intracellular calcium in rat vascular smooth muscle.

Although the pineal gland influences several physiological systems, only a few studies have investigated its role in the intermediary metabolism. In the present study, male Wistar rats, pinealectomized or sham-operated 6 wk before the experiment, were submitted to both intravenous glucose tolerance tests (IVGTT) and insulin binding as well as glucose transport assays in isolated adipocytes. The insulin receptor tyrosine kinase activity was assessed in liver and muscle. The insulin secretory response during the IVGTT was impaired, particularly in the afternoon, and the glucose transport responsiveness was 33% lower in pinealectomized rats. However, no difference was observed in the insulin receptor number of adipocytes between groups as well as in insulin-stimulated tyrosine kinase activity, indicating that the initial steps in the insulin signaling were well conserved. Conversely, a 40% reduction in adipose tissue GLUT-4 content was detected. In conclusion, pinealectomy is responsible for both impaired insulin secretion and action, emphasizing the influence of the pineal gland on glucose metabolism.

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Effect of chlorpropamide on glucose transport in rat adipocytes in the absence of changes in insulin binding and receptor-associated tyrosine kinase activity

Metabolism ◽

10.1016/0026-0495(87)90165-x ◽

1987 ◽

Vol 36 (6) ◽

pp. 548-554 ◽

Cited By ~ 20

Author(s):

D.B. Jacobs ◽

G.R. Hayes ◽

D.H. Lockwood

Keyword(s):

Tyrosine Kinase ◽

Glucose Transport ◽

Kinase Activity ◽

Insulin Binding ◽

Tyrosine Kinase Activity ◽

Rat Adipocytes

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Insulin potentiates receptor mediated tyrosine kinase activity, and glucose transport in bovine lens

Experimental Eye Research ◽

10.1016/0014-4835(92)90386-7 ◽

1992 ◽

Vol 55 ◽

pp. 51

Author(s):

D.B. Jacobs ◽

M. Ireland ◽

H. Dagher ◽

H. Maisel ◽

G. Granberger

Keyword(s):

Tyrosine Kinase ◽

Glucose Transport ◽

Kinase Activity ◽

Tyrosine Kinase Activity ◽

Bovine Lens

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Functional reconstitutional of the human epidermal growth factor receptor system in Xenopus oocytes.

The Journal of Cell Biology ◽

10.1083/jcb.111.4.1661 ◽

1990 ◽

Vol 111 (4) ◽

pp. 1661-1671 ◽

Cited By ~ 21

Author(s):

L K Opresko ◽

H S Wiley

Keyword(s):

Tyrosine Kinase ◽

Intracellular Calcium ◽

Oocyte Maturation ◽

Mammalian Cells ◽

Xenopus Oocytes ◽

Kinase Activity ◽

Egf Receptor ◽

Biological Activities ◽

Tyrosine Kinase Activity ◽

Receptor System

We have expressed the human EGF receptor (hEGF-R) in Xenopus oocytes by injecting mRNA synthesized in vitro using SP6 vectors containing receptor cDNAs. Each oocyte could express over 1 x 10(10) receptors of a single affinity class and these were able to bind and rapidly internalize EGF. Occupancy resulted in receptor tyrosine autophosphorylation, downregulation, and release of intracellular calcium. Occupied receptors also rapidly induced meiotic maturation in stage VI oocytes. Receptors lacking tyrosine kinase activity bound EGF normally, but did not downregulate or induce any biological responses. The rate of oocyte maturation was proportional to hEGF-R occupancy and was significantly faster than progesterone-induced maturation at nanomolar EGF concentrations. Mutant hEGF-R truncated at residue 973 displayed identical phenotypes in both mammalian cells and oocytes in that they were defective in their ability to release intracellular calcium, undergo ligand induced internalization and receptor downregulation. However, these receptors were fully capable of inducing oocyte maturation. The remarkable retention of specific biological activities of different hEGF-R in the context of oocytes suggests that this receptor system interacts with generally available cellular components that have been conserved during evolution. In addition, it suggests that cell surface tyrosine kinase activity may play an important role in regulating resumption of the cell cycle.

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