MODULATION OF PORPHYRIN DERIVATIVES ACCUMULATION IN C6 GLIOMA-CELLS BY DRUGS ACTING ON BETA-ADRENERGIC RECEPTORS - A SPECTROFLUOROMETRIC STUDY

The pharmacological modulation of the uptake of porphyrin derivatives in cultured C6 glioma cells was investigated by means of spectrofluoro metric analysis both in single cells and in cell homogenates. The infl uence of drugs acting as beta-receptor agonists or antagonists was stu died in cells grown to semiconfluency. Isoproterenol (ISO), a beta-rec eptor agonist, enhanced the intracellular fluorescence intensity of bo th Photofrin and protoporphyrin IX (PpIX). A treatment with a beta-rec eptor antagonist I-propranolol (PRO), simultaneous with ISO, resulted in an intracellular Photofrin fluorescence signal comparable to that o f the control cells, indicating the specificity of the pharmacological action. The pharmacological treatment seemed particularly effective w ith the aggregated species. This is suggested by the relative increase of the band at 670 ram, being greater than that in the 630 nan band i n the emission spectra of Photofrin and PpIX, and by the comparison of the fluorescence intensity on cell homogenates measured both in the a bsence and in the presence of cetyltrimethyl-ammonium bromide as a det ergent.