NEURONAL AND GLIAL PROSTAGLANDIN-D SYNTHASE ISOZYMES IN CHICK DORSAL-ROOT GANGLIA - A LIGHT-MICROSCOPIC AND ELECTRON-MICROSCOPIC IMMUNOCYTOCHEMICAL STUDY

Homogenates of chick dorsal root ganglia (DRG) and in vitro cultures o f DRG neurons are known to synthesize prostaglandin (PG) D-2. To speci fy the PGD synthase isozymes controlling PGD(2) synthesis in DRG and t o identify the DRG cells responsible for this synthesis, we applied po lyclonal antibodies raised against rat brain or rat spleen PGD synthas e isozymes to vibratome or cryostat slices of DRG previously fixed wit h a formaldehyde-lysine-periodate mixture and permeabilized with Trito n X-100. The immunoreactivity indicating rat spleen PGD synthase, a gl utathione (GSH)-requiring enzyme, was located in satellite cells encom passing particular large neurons of class A and in Schwann cells myeli nating and enwrapping their initial axonal segments. In contrast, the immunoreactivity of rat brain PGD synthase, a GSH-independent enzyme, was restricted to particular ganglion cell perikarya: 33% of the DRG n eurons were immunostained for rat brain PGD synthase, including 2% of large class A neurons and 40% of small class B neurons. Only 3.3% of r at brain PGD synthase-immunoreactive small B neurons coexpressed subst ance P, indicating that the immunoreactive neurons belong to the B-1 s ubclass. By electron microscopy, 71 of 72 immunoreactive DRG cells wer e identified as small B neurons of the B-1 subclass, and 71 of 77 B-1 neurons were immunoreactive for rat brain PGD synthase. These results demonstrate that PGD(2) formation in DRG is regulated by two isozymes: the GSH-requiring isozyme located in satellite and Schwann cells and the GSH-independent isozyme-confined to small B-1 neurons.