Calciseptine (Recombinant). CaS. Specific L-type Cav channel blocker. Calciseptine (Recombinant) is a natural peptide isolated from the Dendroaspis p. polylepsis black mamba venom, by a modification to the procedure of Schweitz et al. and purified to homogenity. Calciseptine (Recombinant) was shown to be a specific L-type Cav channel blocker. In contrast, it increases L-type currents in skeletal muscle. Calciseptine (Recombinant) blocks spontaneous or K+-induced contraction of cardiac and smooth muscle cells. Using patch clamp, it was also shown to block specifically L-type Cav channel current in neuronal cells in culture. For these varieties of effects, the IC50's were in the range of 15-500 nM. Using the outside-out configuration of patch clamp, it was shown to reduce single L-type channels open probability and availability as recorded from Guinea pig portal vein. Ion Channel Modulators; Voltage - Gated Ca2+ Channel Blockers.