Figure 3.

Representative experiments (of a group of seven tissues) of the action of Cd²⁺ added to the basolateral solution on the dynamics of TJ opening and closing. The urinary bladders were short-circuited and bathed on the apical side by 75 mM KCl and on the basolateral side by NaCl Ringer's solution. (A) Basolateral Ca²⁺ was replaced by 1 mM Cd²⁺ ((Ca × Cd)_bl) with no resulting increase of TER. Afterwards, Cd²⁺ was removed from the basolateral solution (−Cd_bl) leading, after a few seconds, to an increase of TER that can be terminated by reintroduction of Ca²⁺ (1 mM) into the basolateral fluid (+Ca_bl). No recovery of TER was observed in response to reintroduction of Ca²⁺, in contrast to control tissues. (B) Cd²⁺ was added to the basolateral solution (in the presence of 1 mM Ca²⁺) at concentrations of 0.2 mM (+Cd_bl 0.2) and 1.0 mM (+Cd_bl 1.0). Subsequently, Cd²⁺ was removed (−Cd_bl) without any noticeable effect. Afterwards, basolateral Ca²⁺ was also removed (−Ca_bl), leading to a conspicuous decrease of TER that fully reverts upon readmission of Ca²⁺ into the basolateral fluid (+Ca_bl). The vertical deflections of SCC, caused by pulses of ±1 mV in the clamping potential, are proportional to the overall tissue electrical conductance (G), where G = 1/TER.