Microvesicles in endocrine cells are the morphological and functional equivalent of neuronal synaptic vesicles. Microvesicles accumulate various neurotransmitters through a transmitter-specific vesicular transporter energized by vacuolar H(+)-ATPase. We found that mammalian pinealocytes, endocrine cells that synthesize and secrete melatonin, accumulate l-glutamate in their microvesicles and secrete it through exocytosis. Pinealocytes use l-glutamate as either a paracrine- or autocrine-like chemical transmitter in a receptor-mediated manner, resulting in inhibition of melatonin synthesis. In this article, we briefly describe the overall features of the microvesicle-mediated signal-transduction mechanism in the pineal gland and discuss the important role of acidic organelles in a novel regulatory mechanism for hormonal synthesis and secretion.
Synaptic-like microvesicles, synaptic vesicle counterparts in endocrine cells, are involved in a novel regulatory mechanism for the synthesis and secretion of hormones
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Y. Moriyama, M. Hayashi, H. Yamada, S. Yatsushiro, S. Ishio, A. Yamamoto; Synaptic-like microvesicles, synaptic vesicle counterparts in endocrine cells, are involved in a novel regulatory mechanism for the synthesis and secretion of hormones. J Exp Biol 1 January 2000; 203 (1): 117–125. doi: https://doi.org/10.1242/jeb.203.1.117
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