Gene expression, cellular localization, and enzymatic activity of diacylglycerol kinase isozymes in rat ovary and placenta

Female reproductive organs show remarkable cyclic changes in morphology and function in response to a combination of hormones. Evidence has accumulated suggesting that phosphoinositide turnover and the consequent diacylglycerol (DG) protein kinase C (PKC) pathway are intimately involved in these mechanisms. The present study has been performed to investigate the gene expression, cellular localization, and enzymatic activity of the DG kinase (DGK) isozymes that control the DG-PKC pathway. Gene expression for DGK alpha, -epsilon, -zeta, and -iota was detected in the ovary and placenta. Intense expression signals for DGK zeta and -alpha were observed in the theca cells and moderate signals in the interstitium and corpora lutea of the ovary. On the other hand, signals for DGK epsilon were seen more intensely in granulosa cells. In the placenta, signals for DGK alpha and -iota were observed in the junctional zone, whereas those for DGK zeta were detected in the labyrinthine zone. At higher magnification, the signals for DGK alpha were mainly discerned in giant cytotrophoblasts, and those for DGK iota were found in small cytotrophoblasts of the junctional zone. DGK zeta signals were observed in all cellular components of the labyrinthine zone, including mesenchyme, trabecular trophoblasts, and cytotrophoblasts. DGK epsilon signals were detected in the junctional zone on day 13 and 15 of pregnancy and were diffusely distributed both in the labyrinthine and junctional zones at later stages. The present study reveals distinct patterns of mRNA localization for DGK isozymes in the rat ovary and placenta, suggesting that each isozyme plays a unique role in distinct cell types in these organs.