Localization of GABA, GAD65 and GAD67 in rat epiphyseal growth plate chondrocytes

The distribution of gamma -aminobutyrate (GABA) and its synthesizing enzyme glutamate decarboxylase (GAD) in the epiphyseal growth plate of the rat lo ng bone was studied by immunohistochemistry. GAGA, GAD65 and GAD67 immunore active chondrocytes were found in hypertrophic zones of the growth plate, b ut not in reserve and proliferative zones. In the hypertrophic zone, GABA i mmunoreactivity was more intense in the maturation zone than in the degener ative zone and the zone of provisional calcification. Patterns of immunorea ctivity for GAD65 and GAD67 were almost comparable to those of GABA. In add ition, GAD65 and GAD67 mRNAs were detected by reverse transcriptase-polymer ase chain reaction (RT-PCR). These results suggest that GABA, which is synt hesized de novo in chondrocytes of the growth plate may have certain functi onal roles in skeletal growth.