钠对于蟾蜍（尾蟾尾蟾）肾上腺嗜铬细胞的刺激-分泌偶联是否必要？

Is sodium necessary for stimulus-secretion coupling in toad (Caudiverbera caudiverbera) adrenal chromaffin cells?

Nassar-Gentina V, Aguilar P, Luxoro M

Laboratorio de Fisiologia Celular, Facultad de Ciencias, Universidad de Chile, Vina del Mar.

Comp Biochem Physiol Comp Physiol. 1992 Aug;102(4):745-9. doi: 10.1016/0300-9629(92)90735-9.

Abstract

Chromaffin cells of the toad were used to investigate the effects of total replacement of extracellular Na+ by monovalent cations or sucrose on secretion of catecholamine (CA). 2. K+, Rb+ or Cs+ in place of Na+ produced an immediate secretory response, which are dependent on extracellular Ca2+ and it was blocked by Co2+. Li+ or choline+ did not affect basal secretion. 3. Isosmotic replacement of Na+ by sucrose caused CA secretion even in the absence of external Ca2+ or in the presence of Ca-channel blockers. 4. Tetraethylammonium decreased the extent of CA release produced by either K+ or Rb+. 5. The secretagogue effect of Na+/K+, Na+/Rb+ or Na+/Cs+ replacement could be explained by a depolarization of the cell membrane, which ultimately will cause Ca2+ influx through voltage-dependent Ca-channels. However, the present results indicate that Na+ may be sufficient but not necessary for CA secretion.

摘要

用蟾蜍的嗜铬细胞来研究用单价阳离子或蔗糖完全替代细胞外钠离子对儿茶酚胺（CA）分泌的影响。2. 用钾离子、铷离子或铯离子替代钠离子会立即产生分泌反应，这种反应依赖于细胞外钙离子且会被钴离子阻断。锂离子或胆碱离子不影响基础分泌。3. 用蔗糖等渗替代钠离子即使在没有细胞外钙离子或存在钙通道阻滞剂的情况下也会引起CA分泌。4. 四乙铵降低了由钾离子或铷离子产生的CA释放程度。5. 用钠离子/钾离子、钠离子/铷离子或钠离子/铯离子替代所产生的促分泌作用可以通过细胞膜的去极化来解释，这最终会导致钙离子通过电压依赖性钙通道内流。然而，目前的结果表明钠离子对于CA分泌可能是充分的但不是必要的。