Abstract
To study the regulation of hPL secretion, a monolayer culture of human term trophoblast was utilized. Time course of spontaneous secretion for 5 rain to 21 hr showed a steady rate of secretion at 15±1.1 ng/106 cells/hr. Intracellular hPL was constant at 34±4 ng/106 cells. K+ (21 mM) produced a slight but significant increase, from 457±13 to 584±15 ng/106 cells. GHRF (5 × 10−10 M) stimulated hPL secretion by 39±7%. Both dibutyryl cyclic AMP (dbcAMP) and Ca++ had inhibitory effects on secretion. dbcAMP inhibited secretion by 49±3%. This effect disappeared in the presence of verapamil, the Ca-channel blocker. Ca-ionophore A23187 inhibited secretion by 30±4%. EGTA and verapamil stimulated secretion by 116±11% and 16±1.1%, respectively. The Ca-calmodulin inhibitor tirffluoperazine eliminated the A23187 effect. It also interfered with the inhibitory effect of dbcAMP. It is concluded that: 1) the secretory mechanism of hPL is a unique process in which both dbcAMP and calcium exert inhibitory action; 2) the two messengers interrelate: dhcAMP modifies calcium, which requires a calmodulin complex for its effect; 3) by analogy to other secretory mechanisms, the major amount of hPL is secreted by a constitutive mechanism with only small intracellular storage pools; and 4) the concept of the hypothalamic-pituitary analogy applies to a small fraction of hPL secretion.
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Hochberg, Z., Perlman, R. & Bick, T. INTRACELLULAR REGULATION OF PLACENTAL LACTOGEN (hPL) SECRETION BY CULTURED HUMAN TROPHOBLAST. Pediatr Res 20, 1180 (1986). https://doi.org/10.1203/00006450-198611000-00040
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DOI: https://doi.org/10.1203/00006450-198611000-00040