The effects of platelet-activating factor on the output of prostaglandins from the guinea-pig uterus.
Platelet-activating factor (PAF) significantly increased the output of prostaglandin (PG) F2 alpha from the guinea-pig uterus during the mid-cycle phase (Days 6-10), but only had a small, non-significant stimulatory effect on the outputs of PGE2 and 6-keto-PGF1 alpha. PAF significantly increased the outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha from the guinea-pig uterus during the later phase of the cycle (Days 15-17). Lack of extracellular calcium did not affect the stimulatory effect of PAF on uterine PG output. However, TMB-8 (an intracellular calcium antagonist) prevented the increases in uterine PG output produced by PAF at both phases of the cycle. These results suggest that the stimulatory effect of PAF on uterine PG output in the guinea-pig is dependent upon the mobilization of intracellular calcium but is not dependent upon the uptake of extracellular calcium. Also, the weak stimulatory effect of PAF on PGE2 output from the uterus during the mid-cycle phase indicates that, if PAF is involved in implantation in guinea-pigs, it probably does not act via PGE2. Also, the lack of an inhibitory effect of PAF on uterine PGF2 alpha synthesis and release suggests that PAF is not the anti-luteolytic factor produced by the guinea-pig conceptus during early pregnancy.
Norman
S J
SJ
Department of Pharmacology, University of Endinburgh Medical School, UK.
Poyser
N L
NL
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004971:Estrus / Q000502:physiology*; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010477:Perfusion; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011247:Pregnancy; D011453:Prostaglandins / Q000378:metabolism*; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism*
D002121:Calcium Channel Blockers; D010972:Platelet Activating Factor; D011453:Prostaglandins; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D002118:Calcium