Alterations of islet microvasculature in mice treated with low-dose streptozocin

Islet capillary area was followed daily in mice after treatment with low-dose streptozocin (LDS), in order to elucidate the exact period during which the insular vascular bed undergoes a significant reduction. Forty C57BL6/J mice were diabetized with 5 x 40 mg streptozocin (STZ)/kg body wt and killed 6, 8, 9, 10, 11, 12, 15 or 18 days after the first STZ injection. Pancreases were sectioned and processed by staining for alkaline phosphatases using a method devised by Gomori. The percentage of the islet parenchymal area occupied by intra-islet capillaries was measured using a Videoplan videoanalyzer. LDS treatment did not significantly alter the islet capillary area up to day 8; the first signs of reduction were seen on days 9 and 10 (islet capillary area at days 9 and 10 respectively was 2.68% and 2.60% of controls). At day 11 a dramatic decrease in islet capillary area was seen (1.38%), which was not accompanied by a similar reduction of the islet parenchymal area. The reduction in islet capillary area continued to progress up to day 15 by which time it had achieved the lowest level (0.72%). On day 18, values remained practically unchanged.