Parnova R G, Schakhmatova E I, Plesneva S A, Getmanova E V, Korolev E V, Komissarchik Y Y, Natochin Y V
Sechenov Institute of Evolutionary Physiology and Biochemistry, Saint Petersburg, Russia.
Biochim Biophys Acta. 1997 Apr 24;1356(2):160-70. doi: 10.1016/s0167-4889(96)00175-9.
The water osmotic permeability of frog urinary bladder was found to be increased from 0.08 +/- 0.01 to 1.28 +/- 0.20 microl/min cm2 when serosal bathing medium was changed 4 times for a fresh Ringer solution. High epithelium permeability is accompanied by an increased content of cyclic AMP in the bladder tissue (by 42%, P < 0.01), higher activity of both basal and forskolin-stimulated membrane adenylate cyclase (AC) (by 109% and 74%, respectively, P < 0.05) and by appearance of aggregates of intramembranous particles in the apical membrane. The water flow was inhibited by 10(-9)-10(-5) M prostaglandin E2 (PGE2); the inhibitory effect was eliminated in the presence of 10(-4) M N-ethylmaleimide. The increase of water permeability due to changes of the bathing medium was accompanied by a decrease of serosal PGE2 concentration from 14.8 +/- 1.0 in the 1st solution to 0.6 +/- 0.1 nM in the 5th. 10(-6) M PGE2 in vitro inhibited the activity of membrane AC from highly permeable bladders by 33.4% (P < 0.02). Pretreatment of the membranes with 10 microg/ml pertussis toxin (PT) completely reversed this effect (+149%, P < 0.01). A significant activation of AC was also observed under 10(-10) M PGE2 (by 196%). These data demonstrate that the water permeability could be markedly increased independently of ADH, suggesting that the trigger role in activation of water transport is played by a decreased level of PGE2 which could stimulate AC.
当将浆膜浴液更换4次为新鲜的林格液时，发现青蛙膀胱的水渗透通透性从0.08±0.01增加到1.28±0.20微升/分钟·平方厘米。高上皮通透性伴随着膀胱组织中环磷酸腺苷含量的增加（增加42%，P<0.01）、基础和福斯高林刺激的膜腺苷酸环化酶（AC）活性的升高（分别增加109%和74%，P<0.05）以及顶端膜中膜内颗粒聚集体的出现。水流量受到10^(-9)-10^(-5)M前列腺素E2（PGE2）的抑制；在存在10^(-4)M N-乙基马来酰亚胺的情况下，抑制作用消除。由于浴液变化导致的水通透性增加伴随着浆膜PGE2浓度从第一种溶液中的14.8±1.0降至第五种溶液中的0.6±0.1纳摩尔。10^(-6)M PGE2在体外抑制高通透性膀胱膜AC的活性33.4%（P<0.02）。用10微克/毫升百日咳毒素（PT）预处理膜完全逆转了这种作用（增加149%，P<0.01）。在10^(-10)M PGE2下也观察到AC的显著激活（增加196%）。这些数据表明，水通透性可独立于抗利尿激素而显著增加，提示PGE2水平降低可能在激活水转运中起触发作用，其可刺激AC。
