Stimulation of bovine luteal oxytocin secretion in vitro by a phorbol ester and calcium ionophore.
Experiments were conducted to examine the in vitro effects of a phorbol ester and a calcium ionophore on bovine luteal oxytocin (OT) secretion and synthesis and progesterone secretion. Corpora lutea removed from beef heifers on d 8 of an estrous cycle were sliced and incubated for 2 h with .81 nM 12-O-tetradecanoylphorbol-13-acetate (TPA), 1.62 nM TPA or .3 microM calcium ionophore A23187. Both concentrations of TPA increased (P less than .01) OT secretion (ng.g-1.2 h-1; control, 407.1; .81 nM TPA, 494.7; 1.62 nM TPA, 528.1; SE = 21.2). Increased secretion of OT was accompanied by a corresponding increase (P less than .02) in synthesis of the hormone (ng.g-1.2 h-1; control, 368.5; .81 nM TPA, 427.6; 1.62 nM TPA, 492.1; SE = 25.7). Phorbol ester also induced (P less than .025) progesterone secretion (ng.g-1.2 h-1; control, 1,056.2 vs .81 nM TPA, 1,333.3; SE = 86.4). Calcium ionophore increased (P less than .01) OT secretion (ng.g-1.2 h-1; control, 248.9 vs A23187, 327.4; SE = 16) and there was a trend (P = .09) toward increased synthesis of OT in response to the ionophore (control, 124.4 vs A23187, 165.6; SE = 16.4). Because TPA can activate protein kinase C and A23187 increases intracellular calcium, these intracellular constituents probably are involved in promoting secretion of OT and progesterone.
Cosola-Smith
C A
CA
Dept. of Anim. Sci., Oregon State University, Corvallis 97331.
Appell
L H
LH
Abdelgadir
S E
SE
Stormshak
F
F
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002417:Cattle / Q000378:metabolism*; D003338:Corpus Luteum / Q000187:drug effects* / Q000378:metabolism; D046508:Culture Techniques; D005260:Female; D010121:Oxytocin / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D000001:Calcimycin; D011374:Progesterone; D010121:Oxytocin; D013755:Tetradecanoylphorbol Acetate