Figure 5.

Effects of PK‐THPP on type‐1 cell [Ca²⁺]_i. (A) Recording showing effects of application of two different concentrations (120 and 400 nmol/L) of PK‐THPP causing an abrupt rise in [Ca²⁺]_i. (B) Concentration‐response graph of effects of PK‐THPP on [Ca²⁺]_i. Each point represents mean ± SEM (n = 5–7) and the curve is fit by non‐linear least squares regression to the equation Δ[Ca²⁺]_i = a  +  b. [PK‐THPP]/(EC50 +  [PK‐THPP]). The estimated EC50 is 45.2 nmol/L and the r ² for correlation is 0.19. (C) Effect of Ca²⁺ free Tyrode on [Ca²⁺]_i responses evoked by 400 nmol/L PK‐THPP. Note rapid reduction in [Ca²⁺]_i in the absence of external Ca²⁺. (D) Summary data showing effects of PK‐THPP on Δ[Ca²⁺]_i ([Ca²⁺]_i in the presence of PK‐THPP minus baseline [Ca²⁺]_i) under normal conditions and in the absence of extracellular Ca²⁺. Data are mean ± SEM. Statistical comparison is a paired t test. (E) Effect of 2 mmol/L Ni²⁺, a voltage‐gated Ca²⁺‐channel inhibitor, on [Ca²⁺]_i responses evoked by 400 nmol/L PK‐THPP. Note rapid reduction in [Ca²⁺]_i upon application of Ni²⁺. (F) Summary data showing effects of PK‐THPP on Δ[Ca²⁺]_i under normal conditions and in the presence of Ni²⁺. Data are mean ± SEM. Statistical comparison is a paired t test.