Endocrine Abstracts

Polyunsaturated fatty acids (PUFAs) supply precursors for prostaglandin (PG) synthesis and PGs in turn influence many aspects of reproduction. We have previously demonstrated that supplementation of the diet of dairy cows with the n-6 PUFA [linoleic acid (LA)] significantly inhibited uterine PG production. In this study we have investigated the effects of various n-6 PUFAs in vitro on PG production by ovine endometrial cells.Endometrial tissue was...

Cervical dilatation and myometrial contractions are essential processes of both pre-term and term labour. These processes are associated with enhanced production of 2-series prostaglandins (PGs) from polyunsaturated fatty acids (PUFAs), by feto-placental tissues. Some human epidemiological studies suggest that specific PUFAs can alter the length of gestation. The amnion is a prime site for PG synthesis in the feto-placental unit. Thus perturbations of PG synthesis in this tiss...

The mammalian corpus luteum secretes progesterone under the influence of luteinizing hormone (LH). LH acts by binding to its G-protein coupled receptor and elevating intracellular cAMP thus activating protein kinase A (PKA). However, the exact role of PKA in the regulation of progesterone secretion remains unelucidated. Thus in this study we have investigated the relationship between PKA expression/activity and progesterone secretion during luteinization. Human granulosa cells...

Gonadotrophins such as luteinizing hormone (LH) and human chorionic gonadotrophin (hCG) exert their actions on progesterone (P4) synthesis, at least in part, by regulating luteal cell phosphorylation via ser/thr kinases particularly cAMP-dependent protein kinase (PKA). Hence the aim of this study was to identify changes in P4 secretion and PKA expression during luteinization of human granulosa cells (GCs) in vitro. GCs, obtained from follicular asp...

In human GL cells, 11beta-HSD catalyses the interconversion of cortisol (F) with its inert 11-ketosteroid metabolite, cortisone (E). Since GL cells synthesise prostaglandins (PGs), and PGs have been shown to modulate the expression and activity of the cloned 11beta-HSD enzymes, the objective of the present study was to establish whether locally synthesised PGs affected the net oxidation of F to E by 11beta-HSD in human GL cells recovered from the ovaries of women undergoing co...

Parturition in the ewe is initiated by the fetus following the cortisol rise via activation of the hypothalamic-pituitary-adrenal axis and increased intrauterine PG production. Dietary n-6 PUFAs, noteceably linoleic acid (LA) are the precursors for PG synthesis. The maternal intercotyledonary endometrium is the main site of PGF2alpha during labour. This study investigated the effect of dietary n-6 PUFA supplementation on uterine PG production at term. Ewes (n=32) we...

In human granulosa-lutein (hGL) cells, cortisol (F) is inter-converted with cortisone (E) by 11BHSD. To date two isoforms of 11BHSD have been cloned. Human granulosa cells have been shown to express 11BHSD2 mRNA during the follicular phase of the ovarian cycle, switching to 11BHSD1 mRNA expression as luteinization occurs. However, it is not known whether (1) the protein expression, and (2) the 11BHSD enzyme activities reflect this pattern of mRNA expression. Hence, the aims of...

PGE2 stimulates progesterone synthesis in the primate corpus luteum, apparently via cAMP. Human GL cells express functional EP1 and EP2 receptors via which PGE2 elevates the intracellular calcium and cAMP concentrations respectively (Harris et al, 2001, BBRC 285:1089). In the present study, we have determined the involvement of EP1 and EP2 receptors in the stimulation of cAMP accumulation and progesterone synthesis in these human ovarian cel...

Recent health reports state that the population of western countries is consuming excessive amounts of n-6 polyunsaturated fatty acids (PUFAs) in the diet. Dietary n-6 PUFAs are precursors for prostaglandin (PG) synthesis, which play important roles in parturition. Increased dietary n-6 PUFA could thus alter PG production. This study determined the effect of a high n-6 PUFA diet on PG production and the timing of the onset of labour. Pregnant Welsh Mountain ewes were fed an is...