Johnson A L, Brake J
Department of Animal Sciences, Rutgers, State University of New Jersey, New Brunswick 08903.
Poult Sci. 1992 Jan;71(1):161-7. doi: 10.3382/ps.0710161.
Results from previous studies indicate that the use of dietary zinc may provide an effective means to initiate an induced molt in laying hens. Although much evidence indicates that high concentrations of zinc (10,000 to 20,000 ppm) cause the cessation of lay primarily by depressing feed intake, recent data suggest that lower concentrations (2,800 ppm) in a calcium-deficient diet may act via a direct action on the ovary. Therefore, a series of in vitro studies was conducted to evaluate whether zinc can affect granulosa cell progesterone production. Incubation of granulosa cells from the largest preovulatory (F1) follicle with zinc as zinc sulfate (.1 to 10 microM) had no effect on basal progesterone production. By contrast, ovine luteinizing hormone-stimulated progesterone production was inhibited (P less than .05) in a dose-related fashion by zinc in both the sulfate and acetate forms (1 to 10 microM). Furthermore, zinc attenuated oLH- and forskolin-induced cyclic adenosine monophosphate (cAMP) formation, and inhibited 8-bromo-cAMP- and calcium ionophore (A23187)-induced progesterone production. Such results indicate both pre- and post-cAMP sites of action for zinc's inhibitory actions on progesterone production in F1 granulosa cells. Finally, ovine follicle-stimulating hormone-stimulated cAMP accumulation and progesterone production in granulosa cells collected from 9- to 12-mm follicles (a stage of development representing the early, rapid growth phase) were suppressed (P less than .05) by co-incubation of cells with zinc.(ABSTRACT TRUNCATED AT 250 WORDS)
以往研究结果表明，日粮中使用锌可能是诱导蛋鸡强制换羽的一种有效方法。尽管有大量证据表明，高浓度的锌（10000至20000 ppm）主要通过降低采食量导致产蛋停止，但最近的数据表明，在缺钙日粮中较低浓度的锌（2800 ppm）可能通过对卵巢的直接作用来发挥作用。因此，进行了一系列体外研究，以评估锌是否会影响颗粒细胞孕酮的产生。用硫酸锌形式的锌（0.1至10 microM）孵育最大排卵前（F1）卵泡的颗粒细胞，对基础孕酮的产生没有影响。相比之下，硫酸锌和醋酸锌形式的锌（1至10 microM）均以剂量相关的方式抑制了绵羊促黄体生成素刺激的孕酮产生（P<0.05）。此外，锌减弱了促黄体生成素和福斯可林诱导的环磷酸腺苷（cAMP）形成，并抑制了8-溴-cAMP和钙离子载体（A23187）诱导的孕酮产生。这些结果表明，锌对F1颗粒细胞孕酮产生的抑制作用存在于cAMP作用之前和之后的位点。最后，将细胞与锌共同孵育，抑制了绵羊促卵泡激素刺激的9至12毫米卵泡（代表早期快速生长阶段的发育阶段）颗粒细胞中cAMP的积累和孕酮的产生（P<0.05）。（摘要截断于250字）
