[Blockade of proteasome activity disturbs the rhythm of synthesis of the protein marker of direct cell-cell interactions].

The effect of inhibition of proteasome activity on direct cell-cell interactions in primary hepatocyte cultures was studied. The circahoralian rhythm of protein synthesis was a marker of cell-cell communication. The addition of the proteasome inhibitor MG132 at doses of 10 or 20 μM to the medium with hepatocyte cultures for 19 h resulted in a significant reduction in the total pool of 3H-leucine in cells.

Administration of dopamine to rats disorganizes the rhythm of protein synthesis in hepatocytes.

Dopamine was injected intravenously (9 μg/kg) or intraperitoneally (15 μg/kg) to Wistar rats (3-4 months, 300-400 g). Hepatocytes were isolated 40 min after dopamine injection. Dense cultures were maintained on collagen-coated glasses.

Effect of protein synthesis rhythm-organizing signal persists for a day after single administration of melatonin to rat.

Melatonin administered to rat intraperitoneally organizes ultradian rhythm of protein synthesis in hepatocytes that persists for 1 day after exposure to the synchronizing signal. Hepatocytes were isolated 1 day after melatonin administration and cultured on coverslips in a serum-free medium. In 24 h in culture, the kinetics of protein synthesis was analyzed.

Dopamine disorganizes the rhythm of protein synthesis disrupting self-organization of hepatocytes in vitro.

We studied dense 24-hour cultures of rat hepatocytes in serum-free medium on collagen-coated slides. As before, a circahoralian rhythm of protein synthesis was observed in control cultures in a fresh medium. No rhythm was found after addition of 1-10 μM dopamine to the medium containing such cultures.

[Mesenchymal stromal cells synchronize the rhythm of protein synthesis under the effect of an exogenous signal].

A comparative study was performed of dense 5-hour cultures of rat hepatocytes and equal-density cultures of mesenchymal stromal cells (MSC) isolated from human adipose tissue of rat bone marrow. The cells were grown on collagen-coated class slides in serum-free medium. Unlike in hepatocytes, no rhythm of protein synthesis was initially revealed in MSC, but such a rhythm manifested itself when the culture medium was supplemented with melatonin (2 nM, 5 min).