Expression of Intracellular Calcium Channels and Pumps after Partial Hepatectomy in Rat

Ca²⁺ signals regulate many cellular functions, including proliferation. They are governed by the inositol 1,4,5-trisphosphate receptor (IP₃R), the only intracellular hepatic Ca²⁺ channel and by the endoplasmic reticulum Ca²⁺ pumps, SERCA. To characterise their role in regeneration, expression of their isoforms was studied after 2/3 hepatectomy by real-time quantitative PCR, Western blot and binding studies. We found an early increase in the expression of the IP₃R isoform 1 which contrasted with the decrease of the expression of the IP₃R isoforms 2 and 3 and of SERCA3. This results in a transient switch between IP₃R isoforms 1 and 2, IP₃R isoform 1 becoming predominant before the first round of mitosis. Binding studies detected a 30% diminution of the IP₃R population at 24 h. In conclusion, the Ca²⁺ signalling machinery is regulated, after hepatectomy, by changes in expression of the IP₃R and SERCA isoforms to adapt Ca²⁺ signals to the regenerative state.