Thyrotropin-releasing hormone (TRH) is also present in pancreatic B-cells and its role and regulation here remain unclear. The rat pancreas displays a peculiar ontogenetic pattern for TRH with a rapid increase after birth up to postnatal day 3 when TRH peak is reached. In the present study, dexamethasone (DXM) treatment (1 ¿/g/lOOg BW/day) resulted in an increase of pancreatic weight and retardation of the peak of pancreatic TRH concentration by two days. The TRH-degrading system (either in the 10 000 x g supernatant or in the pellet of pancreatic homogenate) was not stimulated by in vivo DXM treatment. In DXM-treated rats, plasma TSH levels were significantly decreased after postnatal day 1. Plasma glucose concentration was increased on day 1 (i.e. 24 h after the first DXM injection) and decreased to the control level on postnatal day 3. Pancreatic insulin levels were decreased on postnatal day 3 compared to the controls. These results indicate that DXM affects TRH in the neonatal rat pancreas; this effect is probably not mediated through modulation of TRH-degrading activity. The stimulation of pancreatic growth after DXM treatment might be related to the effect on the TRH system.
Prolonged agonist stimulation results in specific transfer of activated Gα subunits of Gqα/G11α family from particulate membrane fraction to soluble (cytosol) cell fraction isolated as 250 000 x g supernatant. In this study, we have used 2D electrophoresis for more defined resolution of Gα subunits of Gqα/G11α family and followed the time course of solubilization effect. The small signal of soluble G proteins was already detected in control, hormone-unexposed cells. Hormone stimulation resulted in a slow but continuous increase of both intensity and number of immunoreactive signals/spots of these G proteins (10, 30, 60, 120 and 240 min). At longer times of agonist exposure (>2 hours), a marked increase of Gqα/G11α proteins was detected. The maximal level of soluble Gqα/G11α proteins was reached after 16 hours of continuous agonist exposure. At this time interval, eight individual immunoreactive signals of Gqα/G1 α proteins could be resolved. The relative proportion among these spots was 15:42:10:11:7:7:2:5. Solubilization of this class of Gα proteins was thus observed after prolonged agonist stimulation only, induced by ultra high concentration of hormone and in cells expressing a large number of GPCRs. Our data therefore rather indicate tight/persisting binding of Gqα/G11α proteins to the membrane., D. Durchánková, J. Novotný, P. Svoboda., and Obsahuje bibliografii a bibliografické odkazy