Jejunal blood flow after exposure to light in rats injected with hematoporphyrin derivative

Experiments were performed to determine the effect of hematoporphyrin derivative (HPD) photodynamic therapy on blood flow to normal rat intestine. A segment of rat jejunum was exposed to red (greater than 590 nm) light (200 mW/cm2) 24 h after the i.v. administration of HPD. Blood flow to the light exposed segment was determined using the radioactive microsphere technique while blood flow to an adjacent light shielded segment of intestine served as an internal control. Animals were divided into six groups of six each: Group I, no HPD, no light; Group II, light, no HPD; Group III, HPD (20 micrograms/g body weight), no light; and Group IV, HPD (20 micrograms/g body weight), light. Blood flow in these four groups was determined 10 min after completion of a 30-min exposure to light. Only in Group IV was there a statistically significant decrease (P less than 0.005) in blood flow to the segment treated with HPD and light. In Groups V [HPD (20 micrograms/g body weight), light] and VI [HPD (10 micrograms/g body weight), light] blood flows were determined 24 h after exposure to light. In both of these groups there was also a significant (P less than 0.05) decrease in blood flow in the segment treated with HPD and light. This study demonstrates that normal intestinal blood flow can be disrupted by HPD photodynamic therapy.