Functional Role of Protein Kinase C during Differentiation of Rat Preadipocytes in Serum-free Culture.

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To delineate the mechanism of the generation of obesity, we investigated the role of protein kinase C during differentiation of preadipocyte. Preadipocytes were obtained from epididymal fat pads of male SD rats, and were cultured in vitro in the presence of insulin, transferrin, and T3. Cells were harvested and the degree of adipose conversion was assessed both by morphology and by glycerol 3-phosphate dehydrogenase activity. For immunoblot studies, specific antibodies to PKC isoforms were used to detect cellular expression of PKC.TPA, an activator of PKC suppressed adipocyte differentiation in. Conversely, staurosporine and H7, inhibitors of PKC, enhanced differentiation and reversed the inhibitory effect of TPA.Immumoblot analysis revealed the expression of PKC-alpha, -delta, -epsilon, and -zeta isoforms in both preadipocytes and mature adipocytes. Expression of PKC-alpha and -epsilon increased during the course of differentiation. TPA down regulated the expression of PKC-alpha and -delta. Activation of PKC suppressed differentiation of rat adipocyte precursor cells. Difference in expression of the isoforms of PKC suggests the differential role of the kinase isoforms as a modulator.