ABSTRACT
The 1950s began with studies on porphyrin uptake by mouse tumors. With partial purification, surprisingly, the hematoporphyrin-rich fractions were among the poorest localizers in tested tumors. Interestingly, too, Mann Chemical Co. supplied us with evaporated residue from the HCl mother liquor remaining after removal of the crystalline "hematoporphyrin" hydrochloride. Porphyrins were precipitated by neutralizing the HCl extracts with an excess of sodium acetate. Porphyrins from the 5% HCl fraction localized in tumors much better than did the purified HP extracted by 1% HCl. A general review and preliminary report of our human studies was published in 1955. A national "Conference on Some Relationships of Porphyrins, Tumors, and Radiosensitivity" was held at the University of Minnesota in 1956, sponsored in part by Merck & Co. Response to ionizing radiation depends heavily on three factors: porphyrin dose, porphyrin type, and tissue type. The porphyrin dose is particularly critical.
