Changes in phosphatase enzymes following denervation of the vallate papilla of the rat

Abstract

Taste buds degenerate following transection of their nerve supply. Phosphatase enzymes associated with the taste buds (adenosine triphosphatase, acid phosphatase) and with the epithelium containing the taste buds (alkaline phosphatase) of the vallate papilla of the rat were studied histochemically and quantitatively at 4 days, 1, 2, 4, and 8 weeks following bilateral (complete) or unilateral (partial) denervation. Four days after bilateral denervation, taste buds were reduced in number. In the remaining degenerating taste buds, adenosine triphosphatase activity decreased, while acid phosphatase activity increased. At 1 week, only occasional fragments of buds were seen which exhibited trace adenosine triphosphatase or acid phosphatase activity. No change was observed histochemically in alkaline phosphatase activity in the superficial epithelium until 2 weeks following bilateral denervation. At this time, activity was greatly reduced and confined to a relatively few superficial epithelial cells. Quantitative studies however showed a significant decrease in alkaline phosphatase activity as early as 1 week after bilateral denervation. At 1 week a 20% decrease in alkaline phosphatase activity occurred followed thereafter by a progressive loss in activity of 50% at 2 weeks, 55% at 4 weeks, and 58% at 8 weeks postoperatively. Unilateral (partial) denervation did not produce any detectable histochemical or quantitative changes in adenosine triphosphatase, acid or alkaline phosphatase activity. The results demonstrate that enzymes both in the taste buds and in the associated epithelium require an intact innervation for their expression. This “trophic” dependence of enzymes on an intact innervation may be one way the nerve influences cell metabolism, regeneration, and cytodifferentiation.