Steroid hormone actions at the plasma membrane: Induced calcium uptake and exocytotic events

Abstract

Calcium as an intracellular second messenger is not a new concept, although the subject is undergoing a resurgence in interest, in part reflecting our current appreciation of calcium channels and their role in Ca2+ influx, as well as the regulation of cytoplasmic Ca2+ movements by phosphoinositide metabolism (Michell, 1986). Perhaps the most intriguing aspect of the topic is that the agonists are not restricted to a single structural class, but include neurotransmitters, peptide hormones, and steroid hormones (see Table 1). Parallels in signal transduction between divergent structural classes of regulatory substances have been proposed before (Szego, 1978). The current work will attempt to focus more closely on systems where agonist-mediated changes in cellular calcium culminate in an exocytotic event.