Comitato Raffaella, Esposito Teresa, Cerbo Giovanna, Angelini Francesco, Varriale Bruno, Cardone Anna
Department of Biological Science, Section of Evolutionary and Comparative Biology, University of Naples Federico II, Italy.
J Exp Zool A Comp Exp Biol. 2006 Mar 1;305(3):288-98. doi: 10.1002/jez.a.264.
In mammals, retinoic acid is involved in the regulation of testicular function by interaction with two families of nuclear receptors, retinoic acid receptor (RAR) and retinoid X receptor (RXR). Among RAR isoforms, the testicular cells of the lizard were found to express only RARalpha (3.7 kb) and RARbeta (3.4 kb) mRNAs, as reported here. In this study, the effects of exogenous all-trans-retinoic acid (atRA) on spermatogenesis of a non-mammalian seasonal reproducer were investigated. Daily intraperitoneal injections of atRA or atRA plus testosterone (atRA+T) were given for 2 weeks to adult males of the lizard Podarcis sicula. In animals treated with atRA, the seminiferous tubules were markedly reduced in cross-area. The seminiferous epithelium collapse was responsible for a sensible reduction in the number of germ cells and disruption in normal epithelial organization. In comparison, in atRA+T-treated lizards the loss of germinal cells was significantly less. The loss of germ cells observed in both experimental groups results from an induction of apoptotic process, as revealed by TUNEL analysis. Although low in number, apoptotic germ cells were also observed in the control groups (saline- and T-treated lizard), where the main germ cells undergoing apoptosis are primary spermatocytes (most frequently) and some spermatogonia. In conclusion, it is shown here that retinoic acid has deleterious effects on lizard spermatogenesis, causing a severe depletion of seminiferous epithelium, probably via induction of apoptotic processes. These effects are not completely inhibited by simultaneous administration of testosterone, although this hormone, once injected, is able to stimulate spermatogenesis and protect germinal cells from apoptotic cell death.
在哺乳动物中，视黄酸通过与两类核受体，即视黄酸受体（RAR）和类视黄醇X受体（RXR）相互作用，参与睾丸功能的调节。如本文所报道，在RAR亚型中，蜥蜴的睾丸细胞仅表达RARα（3.7 kb）和RARβ（3.4 kb）的信使核糖核酸。在本研究中，调查了外源性全反式视黄酸（atRA）对一种非哺乳动物季节性繁殖者精子发生的影响。对成年雄性意大利壁蜥每天进行腹腔注射atRA或atRA加睾酮（atRA+T），持续2周。在用atRA处理的动物中，生精小管的横截面积明显减小。生精上皮的塌陷导致生殖细胞数量显著减少，并破坏了正常的上皮组织结构。相比之下，在atRA+T处理的蜥蜴中，生殖细胞的损失明显较少。两个实验组中观察到的生殖细胞损失是由凋亡过程的诱导引起的，这通过TUNEL分析得以揭示。尽管数量较少，但在对照组（生理盐水处理组和睾酮处理组蜥蜴）中也观察到了凋亡的生殖细胞，其中主要经历凋亡的生殖细胞是初级精母细胞（最常见）和一些精原细胞。总之，本文表明视黄酸对蜥蜴的精子发生具有有害影响，可能通过诱导凋亡过程导致生精上皮严重耗竭。尽管这种激素一旦注射能够刺激精子发生并保护生殖细胞免于凋亡性细胞死亡，但同时给予睾酮并不能完全抑制这些影响。
