48 research outputs found
Release of prostaglandins from the uterus
There is much evidence for the existence of a luteolytic hormone (luteolysin)
secreted by the uterus towards the end of the oe3trous cycle or pseudopregnancy in
several mammalian species. Its chemical identity is unknown. Distension of the
uterus by the insertion of a foreign body or the systemic administration of oestrogen causes early regression of the corpora lutea due to the premature release of
this hormone.There is much evidence for the existence of a luteolytic hormone (luteolysin)
secreted by the uterus towards the end of the oestrous cycle or pseudopregnancy in
several mammalian species. Its chemical identity is unknown. Distension of the
uterus by the insertion of a foreign body or the systemic administration of oestrogen causes early regression of the corpora lutea due to the premature release of
this hormone.Prostaglandin Fâα. possesses potent luteolytic activity in all of the species
so far tested. Consequently experiments have been performed to investigate whether
the uterine luteolytic hormone could be this prostaglandin.Distension of the guinea-pig uterus in vitro and the sys tonic administration of
oestrogen to guinea-pigs were found to release prostaglandin Fâα from the uterus.
The analysis of uterine venous blood samples taken from cycling sheep and guineapigs
showed prostaglandin Fâ α to be present in levels higher at the end of the
oestrous cycle than at times earlier. Also the uterine venous blood of guineapigs
contained a high level of prostaglandin Eâ at the end of the cycle.In sheep with an ovary autotransplanted to the neck, cyclic activity ceases.
The fluid which often accumulates in the uterus of such sheep has been analysed
and was found to contain large amounts of prostaglandin Fâ α. In addition, prostaglandin F-like activity was detected in the uterine venous blood but not the
carotid arterial blood of one of these sheep. The results of these findings are
discussed.Prostaglandins Fâα and Eâ were present in guinea-pig uterine tissue in small
amounts at the end of the oestrous cycle. Guinea-pig uteri taken on selected days
throughout the cycle were found capable of biosynthesising prostaglandins Fâ α and
Eâ from endogenous precursors during, incubation in vitro. On any one day, 4 to 5 times
more prostaglandin Fâα than Eâ was produced, with greater amounts of each being formed
nearer to the end of the oestrous cycle. Indomethacin inhibited this synthesis of
prostaglandins.The results obtained in this work support the hypothesis that the uterine luteolytic
hormone (luteolysin) is prostaglandin Fâα. This view is discussed in relation to connected findings and observations reported by other workers
The effects of P2Y receptor agonists and adenosine on prostaglandin production by the guinea-pig uterus
1. This study has investigated the effects adenosine 5âČ-triphosphate (ATP), analogues of ATP, uridine 5âČ-triphosphate (UTP) and adenosine on prostaglandin output from the guinea-pig uterus superfused in vitro, and from guinea-pig endometrium and myometrium cultured for 24âh. 2. ATP, 2-methylthio ATP and adenosine increased the outputs of prostaglandin F(2α) (PGF(2α)) and 6-keto-PGF(1α) (reflecting PGI(2) production), and UTP increased the output of PGF(2α) from the superfused guinea-pig uterus. These findings support the hypothesis that the contractile effects of ATP, 2-methylthio ATP, UTP and adenosine are mediated by prostaglandins. 3. Suramin (a P2 receptor antagonist) and 8-sulphophenyltheophylline (an A receptor antagonist) blocked the stimulatory actions of ATP and adenosine, respectively, on PGF(2α) output, suggesting that ATP acts on P2 receptors (probably of the P2Y type) and adenosine acts on A receptors in the guinea-pig uterus to increase PGF(2α) production. 4. ATP, 2-methylthio ATP, α,ÎČ-methylene ATP, ÎČ,Îł-methylene ATP, UTP and adenosine increased the output of PGF(2α) from guinea-pig endometrium and myometrium after 24âh of culture, with a greater stimulatory effect being exerted on the endometrium than on the myometrium. Little or no stimulatory effect was seen after 2 and 8âh of culture. In addition the effects of ATP, ATP analogues, UTP and adenosine on the outputs of PGE(2) and 6-keto-PGF(1α) from cultured endometrium and myometrium were more variable, with both stimulation and inhibition being observed. 5. The stimulatory effects of ATP and adenosine on PGF(2α) output from the endometrium and myometrium were associated with an increase in the prostaglandin synthesizing capacity of both tissues, due probably to an increase in the amount of prostaglandin H synthase present