Age-related changes in the localization of P2X (nucleotide) receptors in the rat adrenal gland

Abstract

Observation of the changes in the occurrence and distribution of nucleotide (P2X) receptors in the adrenal gland during development and ageing, and correlation with the changes in adrenal status at similar stages may give morphological insights into the functions of purine nucleotides in the gland. Age-related changes in the localization of all seven subtypes of the P2X receptor in the adrenal gland of rat were therefore investigated immunohistochemically. In the adrenal glands of prenatal rats, immunoreactivity to P2X receptor subtypes was not observed. In glands of the postnatal rat at the developmental stages studied, only immunoreactivity for the P2X5 receptor subtype was observed. A small number of faintly P2X5-immunoreactive chromaffin cells were found in the adrenal glands of 1-day-old rats; the frequency of localization and intensity of staining of immunoreactive cells had increased by day 4 and was further increased at day 7. P2X5 immunoreactivity was not observed in the adrenal glands from 14- and 21-day-old rats. At 8 weeks of age, immunoreactivity with a specific distribution for each of the seven receptor subtypes was observed. Except for the P2X4 receptor, adrenal glands at 24 months showed a similar pattern of immunoreactivity for the receptor subtypes as that observed at 8 weeks. Immunoreactivity for P2X4 was first observed in the adrenal cortical cells of the zona reticularis at 8 weeks, but was absent in 24-month-old rats. However, several P2X4-immunoreactive chromaffin cells appeared at 24 months. Such immunoreactive cells were not seen in rats of any of the other ages studied. It was concluded that the greater expression of P2X5 receptor at an early developmental stage and of P2X4 in ageing might reflect functional roles for purines in cellular proliferation and/or differentiation, and in cellular degeneration, respectively, in adrenal glands of rat.