Changes in morphology of endocytotic vesicles in cardiac capillary endothelial cells and myocytes of rats after treatment with adenine and AMP.

Isolated rat hearts were perfused with media containing no additions (sham), adenine, or AMP to determine if adenine or AMP would affect post-ischaemic myocyte ultrastructure. The most significant change induced by both adenine and AMP was a dramatic increase in the number and size of endocytotic vesicles apparent in capillary endothelia and myocytes. This observation suggests endocytosis as a possible transport mechanism for AMP or adenine, or other large polar molecules including purine nucleotide precursors, from the coronary circulation across capillary endothelia and into myocytes.