Agonist-Selective Release of Contents From α-Granules. Model A proposes that granule cargos are distributed in a random manner among α-granules, not in specific subpopulations. Cargo may be clustered with α-granules, given the appearance of segregation and enabling release of specific contents in response to different agonists. Model B postulates that different granule contents are segregated into discrete subpopulations of α-granules that are released in response to different agonists. Angiogenic factors are depicted in green and anti-angiogenic factors depicted in red.