Light-induced induction of contractile dysfunction of smooth muscle during treatment with 5-aminolevulinic acid and Bay K 8644 - a possible alternative in tumor treatment

摘要

Background: Photodynamic therapy (PDT) for tumors is a well-accepted clinical intervention method to destroy tumor cells in gastric or urinary tissues. 5-aminolevulinic acid (ALA) is a naturally occurring compound in the haem biosyn-thetic pathway, which is metabolized to a photosensitive product, protoporphyrin IX (PpIX). In the past, ALA has shown to work well in this context however concentrations of the drug must be high when applied sys-temically. The tumor-selective accumulation of ALA followed by irradiation with visible light induces tumor cell death and apoptosis. The formation of cell-toxic intermediates includes intracellular free calcium as a second messenger and its regulation always plays an important role. In this study we investigated the influence of pharmacologically induced calcium influx via voltage-gated calcium channels induced by the calcium channel agonistic drug Bay K 8644 during ALA-treatment in gastric- and bladder smooth muscle. As an indicator for cellular integrity and function, the contractile response on acetylcholine was used.