Lang R J, Zhang Y
Department of Physiology, Monash-University, Clayton, Victoria, Australia.
J Urol. 1996 Jan;155(1):332-6.
The role of various K+ channel populations in determining the time course and amplitude of the spontaneous action potentials and contractions in the smooth muscle cells of the guinea pig renal pelvis were investigated by standard electrophysiological and tension recording techniques.
Electrical recordings in the proximal renal pelvis were used to demonstrate the presence of 3 cell populations based on the waveform of their Ca(2+)-dependent action potentials which we have termed "pacemaker," "intermediate" and "driven" action potentials.
Blockade of large conductance (BK) or small conductance (SK) Ca(2+)-activated K+ channels with charybdotoxin (30 to 60 nM.) and tetraethylammonium (TEA) (0.5 to 2 mM.) or apamin (200 nM.) increased the duration of the action potentials recorded in "driven" cells. Tetraethylammonium (2 mM.) and 4-aminopyridine (2 mM.) increased the frequency of action potential discharge in both "driven" and "pacemaker" cells, as well as having a positive inotropic and chronotropic effect on the spontaneous contractions of the renal pelvis. In contrast, glibenclamide (0.1 to 1 microM.), Cs2+ (1 mM.) and Ba2+ (100 microM.) had little effect on either the contractile or electrical activity of the renal pelvis.
It was concluded that the frequency of contraction in the proximal renal pelvis is determined by the frequency of action potential discharge in "pacemaker" cells. On the other hand, increases in the amplitude of pelvic contractions may well be correlated with membrane depolarization and/or increases in the duration of the action potentials recorded in "driven" cells.
采用标准电生理和张力记录技术，研究豚鼠肾盂平滑肌细胞中各种钾通道群体在决定自发动作电位的时程和幅度以及收缩方面的作用。
基于近端肾盂中钙依赖性动作电位的波形，通过电记录来证明存在3种细胞群体，我们将其称为“起搏”、“中间”和“驱动”动作电位。
用大电导（BK）或小电导（SK）钙激活钾通道阻滞剂（30至60 nM.的蝎毒素、0.5至2 mM.的四乙铵（TEA）或200 nM.的蜂毒明肽）可增加“驱动”细胞中记录到的动作电位持续时间。2 mM.的四乙铵和2 mM.的4-氨基吡啶可增加“驱动”和“起搏”细胞中动作电位发放的频率，并且对肾盂的自发收缩具有正性变力和变时作用。相比之下，0.1至1 microM.的格列本脲、1 mM.的Cs2+和100 microM.的Ba2+对肾盂的收缩或电活动几乎没有影响。
得出的结论是，近端肾盂的收缩频率由“起搏”细胞中动作电位发放的频率决定。另一方面，肾盂收缩幅度的增加很可能与膜去极化和/或“驱动”细胞中记录到的动作电位持续时间的增加相关。
