Definition: membrane-bound compartments located near the cell membrane with an internal pH of 6.0. Pinocytotic vesicles fuse with early endosomes and, frequently, receptors and ligands are uncoupled here. Receptors are returned to the cell membrane and ligands or other material delivered by pinocytotic vesicles are transferred to late endosomes.
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Examples: glitazone, GI cocktail, etc.