Age-dependent mast-cell-mediated angiogenesis.

In maturing male rats of approximately 5.5,10.5, and 15 weeks of age (groups I, II, and III), the mast-cell-mediated angiogenesis in the mesenterial windows was quantitatively assessed on days 14,21,28, and 35 after the start of intraperitoneal treatment using the mast-cell secretagogue 48/80, and using the saline vehicle. The number of blood vessels per unit length of the central part of the mesenterial window was virtually unaffected by age as well as by the saline treatment. The number of vessels at the mesenterial-window circumference was, however, increased in the older, untreated animals. The postpubescent animals in groups II and III showed a marked mast-cell-mediated angiogenic response lasting until day 28. The relative angiogenic response over the period of 14-28 days clearly increased with advancing age. The highest mean value in group II was about 8 times (p less than 0.001), whereas the highest mean value observed in group III was about 24 times (p less than 0.001) greater than in corresponding saline-treated controls. In contrast, no statistically significant mast-cell-mediated angiogenesis appeared in the prepubescent rats of group I.