PARENT SESSION
Implantation & Early Development

DISTINGUISHING THE FETAL ZONE FROM THE ZONA RETICULARIS OF THE NEONATAL PRIMATE ADRENAL CORTEX BY THE EXPRESSION OF CYTOCHROME B5 AND STEROIDOGENIC ENZYMES.

Mapes, Samantha¹, Tarantal, Alice², Conley, Alan¹, ^{1 2}

ABSTRACT- The primate adrenal cortex is unique in its ability to synthesize the C-19 steroid, dehydroepiandrosterone (DHEA) in free and sulfated (DHEAS) form, from cells of the zona reticularis (ZR) of the mature cortex or the fetal zone (FTZ) of the fetal cortex. The synthesis of DHEA is dependent on expression of cytochrome P450 17-hydroxylase/17,20-lyase (P450c17) and is believed to be promoted by the accessory heme-protein cytochrome b5 (b5). We have examined the developmental expression of b5, P450c17 and 3-hydroxysteroid dehydrogenase (3-HSD) in the adrenal cortex of neonatal rhesus macaques by immuno-cytochemistry to better understand adrenal development and C-19 steroid synthesis. Adrenal glands from 1 and 3 month old neonatal macaques were fixed in 10% buffered formalin, embedded in paraffin, sectioned at 5 and stained using antisera against b5, P450c17 and 3-HSD. The distinct morphologies of both the zona glomerulosa (ZG) and the zona fasciculata (ZF) of the neonatal adrenal cortex resembled those of a mature animal. The distinction between these zones was equally evident by the expression of P450c17 which was obvious in the ZF but not the ZG. 3-HSD expression was evident in both ZG and ZF zones. Beneath the ZF, cells exhibited a more compact morphology. Specifically, the cells in this layer had relatively little cytoplasm compared with those of either the ZF overlying them, or cortical cells nearer the medulla that retained more of the cytoplasm-rich appearance of fetal zone (FTZ) cells. At least some of the cells of this compact zone expressed higher levels of b5 and P450c17 than was evident in FTZ-like cells. Neither the ZG or the ZF exhibited any evidence of b5. Thus, several zones comprised the neonatal macaque adrenal cortex, ZG, ZF, residual FTZ and a fourth compact zone in which some cells exhibit high levels of b5 and P450c17 expression. We propose that this represents the developing ZR, which we have shown previously is characterized by high b5 expression in the adrenal glands of mature macaques. We suggest that the ZR of primates is morphologically and functionally different than the FTZ which, based on weaker b5 and P450c17 expression, seems unlikely to be able make a major contribution to adrenal DHEA or DHEAS secretion during much of fetal development or later in neonatal life.

KEY WORDS: primate, adrenal, androgen, development