In vitro cellular effects of hematoporphyrin derivative.

Several in vitro cell systems were exposed to hematoporphyrin derivative (HPD): established lines of rat kangaroo epithelial kidney; normal mouse embryonic fibroblasts; and differentiated neonatal rat myocardial cells. The uptake of HPD (25 to 100 micrograms/ml) by individual cells occurred rapidly over a 2-hr period and leveled off by 24 hr. HPD was excreted from cells by 48 hr after exposure. However, a low level of HPD (above background) was maintained in cells for up to 4 days following cessation of exposure. Intracellular binding of HPD was to mitochondria as demonstrated by fluorescence microscopy. HPD was also shown to have a growth-inhibiting effect on rat kangaroo cells without added light. The growth effects on mouse cells were less marked.