DIFFERENTIAL PROCESSING OF THE 2 PROLACTINS OF THE TILAPIA (OREOCHROMIS-MOSSAMBICUS) IN RELATION TO ENVIRONMENTAL SALINITY
DIFFERENTIAL PROCESSING OF THE 2 PROLACTINS OF THE TILAPIA (OREOCHROMIS-MOSSAMBICUS) IN RELATION TO ENVIRONMENTAL SALINITY
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DOI：
10.1002/jez.1402640108
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发表时间：
1992-10-15
影响因子：
--
通讯作者：
GRAU, EG
中科院分区：
文献类型：
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作者：
BORSKI, RJ;HANSEN, MU;GRAU, EG
催乳素（PRL）被认为在广盐性硬骨鱼（包括罗非鱼）的淡水适应中起着重要作用。两种PRL（tPRL 188和tPRL 177）已经在罗非鱼脑垂体的最前部分，吻侧远侧部（RPD; Specker等人，'85 a，B; Yamaguchi等人，'88）。我们的研究进行，以确定是否在体内RPD含量的tPRL 188和tPRL 177随环境盐度变化。为此，罗非鱼从卵黄囊吸收期饲养7个月或驯化21和35天的FW或海水（SW）。在一个平行的研究中，我们还研究了是否从FW或SW罗非鱼的RPD的2罗非鱼PRL的释放可能是不同的敏感性，在18-20小时的孵育过程中的介质渗透压的变化。在协议与早期的工作，我们发现，较小的tPRL 177分子是目前在更大的数量在RPD的FW罗非鱼相比，在RPD的SW鱼的内容。对于第一次，我们在这里表明，tPRL 188的含量，tPRL 177一样，也是显着更大的RPD的FW鱼相比，在RPD的SW罗非鱼的量。然而，这两种催乳素在脑垂体中的相对含量或比例依赖于饲养盐度。因此，较大罗非鱼PRL与较小PRL的相对含量或比率（tPRL 188/tPRL 177）在FW罗非鱼的RPD中（1.5：1）显著高于SW鱼（0.75：1）。在低渗或高渗介质中体外孵育18-20小时后，该比值未发生变化，表明比值的变化并非由渗透压引起的差异释放所致。在低渗或高渗介质中孵育18-20小时期间，FW罗非鱼的RPD释放更多的两种形式的PRL比SW鱼的RPD。与以前的研究一致，在罗非鱼的生理范围内的介质渗透压的降低刺激释放tPRL 188和tPRL 177从FW鱼的RPD超过暴露于高渗介质期间观察到的水平。我们在这里首次报告，中等渗透压的降低也刺激了SW鱼RPD中tPRL 188和tPRL 177的释放。在整个实验中，我们没有观察到在我们的孵育条件下tPRL 188和tPRL 177释放之间的差异。FW饲养的鱼，SW和反之亦然，49天的转移改变了2个PRL（tPRL 188/tPRL 177）的比例，观察到的RPD的SW饲养和FW饲养的鱼，分别。总体而言，我们的研究表明，处理的2 PRL可能是不同的敏感性环境盐度。
Prolactin (PRL) is thought to play a significant role in the freshwater (FW) adaptation of euryhaline teleost fishes, including the tilapia, Oreochromis mossambicus. Two PRLs (tPRL188 and tPRL177) have been characterized in the anteriormost portion of the tilapia pituitary, the rostral pars distalis (RPD; Specker et al., '85a,b; Yamaguchi et al., '88). Our studies were undertaken to determine whether the in vivo RPD content of tPRL188 and tPRL177 varied with environmental salinity. To this end, tilapia were reared from the period of yolk-sac absorption for 7 months or acclimated for 21 and 35 days in FW or seawater (SW). In a parallel study, we also examined whether the release of the 2 tilapia PRLs from the RPD of FW or SW tilapia might be differentially sensitive to changes in medium osmotic pressure during 18-20 hr incubations. In agreement with earlier work, we found that the smaller tPRL177 molecule was present in greater quantities in the RPD of FW tilapia compared to the content in RPD of SW fish. For the first time, we show here that the content of tPRL188, like that of tPRL177, is also significantly greater in the RPD of FW fish compared to the quantity in RPD of SW tilapia. Nevertheless, the relative content or ratio of the 2 PRLs in the pituitary was dependent on rearing salinity. Thus, the relative content or ratio of the larger tilapia PRL to smaller PRL (tPRL188/tPRL177) in the RPD of FW tilapia was significantly higher (1.5:1) than that seen in SW fish (0.75:1). This ratio was not altered after 18-20 hr in vitro incubations in hyposmotic or hyperosmotic medium, suggesting that the shift in ratios did not result from differential release by osmotic pressure. During 18-20 hr incubation in either hyposmotic or hyperosmotic medium, the RPD of FW tilapia released more of both forms of PRL than did the RPD of SW fish. Consistent with previous studies, reductions in medium osmotic pressure within the physiological range of the tilapia stimulated the release of both tPRL188 and tPRL177 from RPD of FW fish over levels observed during exposure to hyperosmotic medium. We report here, for the first time, that the reduction of medium osmotic pressure also stimulates the release of both tPRL188 and tPRL177 from RPD of SW fish. Throughout the experiments we did not observe differences between the release of tPRL188 and tPRL177 under our incubation conditions. The transfer of FW-reared fish to SW and vice versa for 49 days altered the ratio of the 2 PRLs (tPRL188/tPRL177) to that observed in the RPD of SW-reared and FW-reared fish, respectively. Overall, our studies indicate that the processing of the 2 PRLs may be differentially sensitive to environmental salinity.