The combination of degradable starch microspheres and angiotensin II in the manipulation of drug delivery in an animal model of colorectal metastasis.

Both biodegradable emboli and pharmacological agents can enhance regional therapy for hepatic targeting. Using a rat model with similar haemodynamic characteristics to human colorectal liver tumour and a radio-labelled marker of similar molecular weight to Adriamycin, we have combined the two approaches to see if the effect was addictive. Following induction of liver tumour in male hooded rats by intrahepatic injection of HSN sarcoma cells, the relative distribution of marker, 99mTc methylene diphosphonate (MDP), was studied in three groups given the following by injection into the hepatic artery. (1) Saline (Control) + MDP; (2) Degradable Starch Microspheres (DSM) + MDP; and (3) Angiotensin II + DSM + MDP. Both Degradable Starch Microspheres alone (P less than 0.001) and Degradable Starch Microspheres + Angiotensin II (P = 0.003) significantly increased the retention of marker in liver and tumour at 1 min following injection, with a 12-fold improvement over controls, but the tumour:liver ratio was unaltered. By 90 min the MDP levels in normal hepatic parenchyma had returned to control values. There was relatively less washout with significant retention in tumour tissue in both DSM (P = 0.03) and combination treated animals (P = 0.001), with a significantly improved (P = 0.001) tumour to liver ratio (5.22:1) in combination treated animal relative to those treated with DSM alone.