A proposed model depicting the biologic events in the formation, storage and releaseof insulin in beta cells is presented. The proposed sequence of events is as follows: intracellular glucose metabolism signals the initiation of proinsulin synthesis in the endoplasmic reticulum; pro-insulin is transferred to the Golgi complex; the conversion of proinsulin to insulin probably occurs in the Golgi complex and intermediate beta granules may be present in this structure; mature beta granules enclosed in smooth membranous sacs are released into the cytoplasm and becomeattached to the microtubular-microfilament system; glucose metabolism initiates the entry of calcium which triggers the change in physical conformation of the microtubules with resultant displacement of the granules to the cell surface where they are released by emiocytosis.

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