title: Time-resolved fluorescence spectroscopy of hematoporphyrin-derivative in human lymphocytes.
abstract: This paper reports on time-resolved microfluorimetric measurements on hematoporphyrin-derivative (HpD)-treated lymphocytes. HpD is at present widely used as a tumor-locating and photosensitizing drug. It is therefore of great importance to study the extent to which the HpD uptake process depends on cell functional and structural properties. Time-resolved fluorescence measurements in single cells are very useful in this respect, since they give information on the content of fluorescent molecules through fluorescence peak-intensity, and, indirectly, on the binding properties through the fluorescence decay times. In particular, we studied the dependence of HpD fluorescence on the cellular functional state. To this end, we performed in-cell fluorescence measurements on human lymphocytes, both in quiescent conditions and in the pre-replicative phase, after stimulation with phytohemagglutinin (PHA). We found a higher HpD content in stimulated lymphocytes. Moreover, we found a spectral band around 575 nm, corresponding to a particular porphyrin species, in which the differences between normal and stimulated lymphocytes are more striking. The porphyrin species emitting in this band seems to play a role in the specific interaction of HpD with tumors, since a similar emission band has also been found in tumor cells containing HpD.
mesh_terms: D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000097:blood*; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents; D013050:Spectrometry, Fluorescence
chemical_list: D006415:Hematoporphyrins; D010835:Phytohemagglutinins; D011838:Radiation-Sensitizing Agents; D017324:Hematoporphyrin Derivative