| Research Abstract |
Homogeneity within populations of mammalian pinealocytes has long been discussed. Several pineal studies have shown the variable localization of hydroxyindole O-methyltransferase(HIOMT), retinal S-antigen, and neuron-specific enolase(NSE). However, in the previous studies describing morphological heterogeneity, no stecific distributions of cell groups are mentioned, with the exception of variations among neighboring pinealocytes.
In the present study, we demonstrated a cortical and medullary arrangement of parenchymal cells in the bovine pineal gland by using antibodies for NSE, synaptophysin(SY-38), and HIOMT as markers of pinealocytes, and glial fibrillary acidic protein(GFAP) as a marker of interstitial cells. Immunoreactive pinealocytes of each antigen examined were more densely distributed in the cortex than in the medulla. In the cortex, GFAP-positive interstitial cells had large intensely-stained soma endowed with several long cytoplasmic processes, whereas in the medulla, they smaller, less intensely labeled perikarya from which numbers of fine short processes emerged. Furthermore, by means of probes specific for HIOMT mRNA, we examined possible differences in melatonin metabolic activity between the cortex and the medulla. An analysis using confocal laser microscopy together with in situ hybridization for HIOMT mRNA showed that the expression of mRNA transcripts in the cortex was more intense than that in the medulla. Our results suggest that the pinealocytes in the cortex are more secretory-like elements than those in the medulla.
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