Riegel JA
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
J Exp Biol. 1999 Apr;202 (Pt 8):947-55. doi: 10.1242/jeb.202.8.947.
Adrenaline and noradrenaline increased the perfusion pressure (Pperf) and single glomerulus filtration rate (SGFR) of perfused hagfish glomeruli. Small amounts (0.1 % or 0.5 %) of bovine serum albumin (BSA) in perfusion fluids containing Ficoll 70 did not diminish the loss of colloid from hagfish glomerular capillaries as has been reported for other perfused capillaries. However, replacement of Ficoll 70 with an osmotically equivalent amount (3 %) of BSA appreciably reduced colloid loss. It was concluded that adrenaline and colloids enhanced flow through the urine-forming capillaries. Whereas adrenaline elevated the SGFR, colloid lowered the SGFR probably by a direct effect on the fluid permeability of the capillary walls. The flow-enhancing effect of adrenaline was used to ensure the exposure of urine-forming capillaries to two inhibitors of active fluid transport, ouabain and 2,4-dinitrophenol (DNP). Both substances lowered the single glomerulus filtration fraction (SGFF), probably by affecting a fluid secretion mechanism. In addition, DNP diminished the flow-enhancing effect of adrenaline. This study provides relatively unequivocal evidence that fluid secretion underlies the formation of primary urine by the hagfish.
肾上腺素和去甲肾上腺素可增加灌注的盲鳗肾小球的灌注压（Pperf）和单个肾小球滤过率（SGFR）。在含有聚蔗糖70的灌注液中加入少量（0.1%或0.5%）牛血清白蛋白（BSA），并不会像其他灌注毛细血管那样减少盲鳗肾小球毛细血管中胶体的流失。然而，用渗透当量的（3%）BSA替代聚蔗糖70可明显减少胶体流失。得出的结论是，肾上腺素和胶体可增强通过形成尿液的毛细血管的血流。肾上腺素可提高SGFR，而胶体可能通过直接影响毛细血管壁的液体通透性来降低SGFR。利用肾上腺素的血流增强作用，确保形成尿液的毛细血管暴露于两种主动液体转运抑制剂——哇巴因和2,4-二硝基苯酚（DNP）中。这两种物质可能通过影响液体分泌机制来降低单个肾小球滤过分数（SGFF）。此外，DNP减弱了肾上腺素的血流增强作用。本研究提供了相对明确的证据，表明液体分泌是盲鳗形成原尿的基础。
