RAPID AND TRANSIENT ALTERATIONS IN TRANSGLUTAMINASE ACTIVITY IN RAT SUPERIOR CERVICAL-GANGLIA FOLLOWING DENERVATION OR AXOTOMY

The activity of transglutaminase (TG), a Ca2+-dependent enzyme contrib uting to cross-linkage formation of intracellular polypeptide chains d ecreased rapidly to ca. 25% of control level in superior cervical gang lia (SCG) within 0.5 h following denervation. The reduced level was ma intained for at least 24 h. By contrast, following axotomy, ganglionic TG activity increased by ca. 50% within 1 h, maintained the increase to 4 h, and returned to control level by 24 h. When SCG were transferr ed to aerobic in vitro incubation conditions 3 h following denervation , the addition of the protein kinase C (PKC) inhibitor, trifluoperazin e (TFP, 10 mug/ml), to the medium partially reversed the denervation-i nduced reduction in ganglionic TG activity. Addition of a PKC activato r, 12-0-tetradecanoylphorbol 13-acetate (TPA, 1 muM), had no effect on the TG activity. These findings suggest that the pathway resulting in the rapid, denervation-induced inhibition of TG activity may involve the transsynaptic activation of PKC. When SCG were placed in vitro 3 h following axotomy, addition of nerve growth factor (NGF, 0.25 mug/ml) to the medium reversed approximately one-half of the axotomy-induced increase in TG activity. Thus, following axotomy, the reduction in del ivery to the SCG of NGF, which can be transported retrogradely within the axon and is indispensable for morphological and functional surviva l of sympathetic neurons, may trigger the transient, axotomy-induced T G activation in the SCG.