The Effects Of ATRA On The Proliferation, Differentiation And Apoptosis Of Rat Preadipocytes

Excessive fat deposition can decrease the ration of lean meat in the carcase and then debase the meat quality. Fat deposition is the result of the proliferation and differentiation of preadipocytes, furthermore, the apoptosis of preadipocytes participates in the regulation of fat deposition, too. Therefore, the research that how to regulate proliferation, differentiation and apoptosis of preadipocytes can provide the academic foundation for the control of fat deposition and references for the livestock breeding and animal production. In this study the effects of ATRA on the proliferation, differentiation and apoptosis of rat preadipocytes were studied on the basis of preadipocyte culture. The male SD rats that used in the experiment are normal, healthy and at the age of 20 days. The effects of ATRA on the proliferation of rat preadipocytes were tested by the method of MTT colorimetry. The results show that 10^-4,10^-5 and 10^-6 mol/L ATRA inhibits the proliferation of preadipocytes and the effects reinforce with the raise of ATRA concentrations. However, 10^-7 and 10^-8 mol/L ATRA promotes the proliferation of preadipocytes and the promotive effects correlate with the concentrations of ATRA negatively. The effects of ATRA on the proliferative activity of preadipocytes were detected by measuring the area of AgNORs in preadipocytes. The results exhibit that AgNORs is stained into black or brown by AgNO3 and locates in the nucleus or nucleolus. The nucleus is stained into straw yellow, but the cytoplasm is not stained. The proliferative activity decreases at the beginning of experiment and then increases, finally it decreases to the lowest point of the full culture process. 10^-4,10^-5 and 10^-6 mol/L ATRA inhibits the proliferative activity of preadipocytes. However, 10^-7 and 10^-8 mol/L ATRA improves the proliferative activity of preadipocytes. The effects of ATRA on the differentiation of preadipocyte were examined by the quantitation of oil red O staining. The results show that 10^-4, 10^-5 and 10^-6 mol/L ATRA inhibits the differentiation of preadipocytes significantly(P<0.01), furthermore, the inhibitive effects of ATRA correlate with ATRA concentrations positively. However, 10-7 and 10-8 mol/L ATRA promotes preadipocyte differentiation significantly(P<0.01) and the promotive effects correlate with ATRA concentrations negatively. The effects of ATRA on the apoptosis of preadipocytes and the expression of Bax and Bcl-2 were analyzed by fluorescent staining of acridine orange and immnocytobiochemistry. The results indicate that 5×10-5 and 10-5 mol/L ATRA improves the expression of Bax but blocks the expression of Bcl-2 and then induces the apoptosis of preadipocytes. The effects of ATRA on the proliferation, differentiation and apoptosis of rat preadipocytes depend on the concentrations of ATRA. The study on the regulatory mechanism of ATRA on the proliferation, differentiation and apoptosis of rat preadipocytes can provide the academic foundation for the control of fat deposition.