Quantitative microvascular changes during azaserine-initiated pancreatic carcinogenesis

Although angiogenesis is considered to be indispensable for continuous tumo ur growth, only very few studies have been published performing microvessel quantification during rumour progression. We measured the tumour vasculari ty in different stages of rat pancreatic carcinogenesis induced by azaserin e and promoted by raw soya flour-containing pancreatotrophic diet. Besides the tumour samples taken at 6 (atypical acinar cell nodules), 15 (adenomas) and 20 (localised adenocarcinomas) months after carcinogen initiation, we also investigated 3 control groups: tumour-bearing host tissue of azaserine -treated rats and normal tissue of untreated rats kept on standard or pancr eatotrophic diet. In contrast with the usual microvessel counting on hot sp ots, we determined microvascular surface density (Sv) and volume density (V v) by electron microscopic morphometry. There was no significant difference in these respect between the control groups, At month 6 after the azaserin e induction Sv and Vv showed slight, nonsignificant decrease as compared to the host control. Both values remained unchanged until the 15th month and increased significantly by the 20th month. These results may indicate compa rable growth rate of tumour and new microvessels in the premalignant stages of carcinogenesis while a more intense angiogenesis than tumour growth aft erwards.