Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Granulosa cells derived from preovulatory bovine follicles were cultured in the presence of insulin-like growth factor-I (IGF-I, 10-100 ng/ml), forskolin (10 microM), or a combination of the two agents. Forskolin alone was the most potent stimulator of both oxytocin (OT) and progesterone (P4) secretion. The two hormones had different patterns of secretion during the course of incubation. OT production peaked on Day 5 of culture and declined thereafter, whereas P4 rose gradually to a peak between Days 7 and 9. The addition of IGF-I to forskolin did not augment OT release beyond that achieved with forskolin alone, but it did maintain higher levels of OT secretion beyond the Day-5 peak. Two antisera, (antiserum I and antiserum II) directed against OT and its C-terminally extended forms, respectively, were used to identify the OT forms in culture media and granulosa cell and corpus luteum extracts. Fully processed OT was detected only in small amounts (0.43 ng/mg protein) in granulosa cell extracts, whereas the corpus luteum extracts contained 6 ng/mg protein. However, granulosa cells that had been incubated with forskolin contained stores of the OT precursor oxytocin-neurophysin, which is found in young corpora lutea. These data indicate that forskolin (whose action probably mimics gonadotropin action) is an effective stimulator of OT biosynthesis and release in cultured bovine granulosa cells.
 ...
PMID:Biosynthesis and release of oxytocin by granulosa cells derived from preovulatory bovine follicles: effects of forskolin and insulin-like growth factor-I. 157 71

Oxytocin is synthesized in the granulosa-derived large cells of the ruminant corpus luteum from a gene which is dramatically up-regulated in the first few days after ovulation. In this work, the regulation of granulosa and luteal cells by prostaglandins and insulin (or insulin-like growth factor-I; IGF-I) has been explored by comparing their effects on oxytocin and progesterone production in cell culture. In granulosa cells, chronic exposure to insulin (17 nmol/l) stimulated luteinization as indicated by increased release of oxytocin and progesterone. Prostaglandin F2 alpha (PGF2 alpha) alone had little effect, but synergized with insulin (or IGF-I) to increase the release of both these hormones. In direct contrast, insulin-stimulated oxytocin production by luteal cells was inhibited by PGF2 alpha. The half-maximal dose (EC50) for PGF2 alpha action in both cell preparations was similar (10-100 nmol/l). Dose-response studies revealed that PGF2 alpha increased the potency of insulin in granulosa cells (EC50 for insulin-stimulation of oxytocin release reduced from 141 to 13 nmol/l by 1 mumol PGF2 alpha/l), but not in luteal cells. Insulin-stimulated oxytocin release from granulosa cells was also synergistically increased by PGE1, PGE2 and forskolin, suggesting this effect to be mediated by adenylate cyclase-coupled PGE receptors. The results reveal that the effects of prostaglandins on oxytocin release are dependent on both the developmental stage of the target tissue and on the presence of other regulators of cellular differentiation. Moreover, they suggest that the increase in responsiveness to insulin and IGF-I, which appears to accompany luteinization in the cow, may be an effect of prostaglandins produced locally during the peri-ovulatory period.
 ...
PMID:Chronic regulation of ovarian oxytocin and progesterone release by prostaglandins: opposite effects in bovine granulosa and early luteal cells. 240 66

Oxytocin is a major peptide product of the ruminant corpus luteum, and the release of oxytocin from serum-free cultures of bovine granulosa cells is stimulated by insulin and insulin-like growth factor-I (IGF-I). Here we have assessed the effects of insulin and IGF-I on oxytocin gene expression in bovine granulosa cells and the dependence of these effects on the developmental status of the cells. When cells from individual follicles were cultured, the estradiol concentration of the follicular fluid was highly correlated with insulin-stimulated oxytocin release. Subsequently, cells were pooled from follicles selected on the basis of estradiol content, and two subsets of cells were distinguished. The first contained highly differentiated cells, as judged by the high estradiol (HE-cells) concentration of the follicular fluid (greater than 40 ng/ml), high levels of LH receptors, and high hCG-stimulated cAMP accumulation. The second subset contained cells from follicles with low estradiol (less than 1 ng/ml; LE-cells) which have fewer LH receptors and low hCG-stimulated cAMP accumulation. Oxytocin production was increased more than 50-fold by insulin (EC50, 230 +/- 57 ng/ml) and IGF-I (EC50, greater than 10 ng/ml), but only in the HE-cells. Oxytocin mRNA was also greatly increased by insulin and IGF-I in the HE-cells only. In contrast, insulin and IGF-I stimulated progesterone release from both HE- and LE-cells. Since oxytocin production is a characteristic of bovine luteal cells, our results support possible roles for IGF-I and insulin in regulation of luteinization or luteal activity. The data suggest that effects of insulin and IGF-I on oxytocin production reflect their effects on oxytocin gene transcription, and that granulosa cells must be appropriately primed (presumably by the in vivo hormonal environment) before they are able to produce oxytocin in response to these polypeptides.
 ...
PMID:Oxytocin production and oxytocin messenger ribonucleic acid levels in bovine granulosa cells are regulated by insulin and insulin-like growth factor-I: dependence on developmental status of the ovarian follicle. 255 59

The effects of streptozotocin-induced diabetes on weight gain, bone growth and GH secretion have been studied in conscious chronically cannulated male rats. In addition to the classic diabetic symptoms (hyperphagia, polydipsia, polyuria, glycosuria and hyperglycaemia), the slow body weight gain (0.95 +/- 0.5 compared with 2.63 +/- 0.5 g/day in non-diabetic controls) was associated with a reduction in bone growth (from 162 +/- 9 to 48 +/- 4 microns/day) and a reduced pituitary GH content (from 1.5 +/- 0.2 to 0.6 +/- 0.06 mg/gland). Serial blood sampling during the day or overnight showed that the normal male episodic GH secretory pattern was obliterated in the diabetic animals. The constant osmotic stimulation of hyperglycaemia and high fluid turnover was reflected in a significant reduction in pituitary oxytocin and arginine vasopressin (AVP) stores. Intravenous insulin infusions (67-1340 pmol/h for 4 or 7 days) caused a large initial weight gain (greater than 20 g in 2 days) followed by a slower increase, and stimulated tibial bone growth (to 100 +/- 16 and 126 +/- 8 microns/day after 4 or 7 days respectively). Insulin infusion for 7 days also increased pituitary GH content (to 1 +/- 0.15 mg/gland), and the normal episodic GH secretory pattern returned. Intravenous infusions of insulin which reduced, but did not completely normalize, blood glucose levels, allowed the resumption of growth and pulsatile GH secretion. Continuous infusion of recombinant human insulin-like growth factor-I (hIGF-I) at 1110 pmol/h for 54 h also caused a large initial rise in body weight in diabetic rats (17.1 +/- 1.6 compared with 7.5 +/- 2.8 g in saline-infused controls) due primarily to increased fluid retention. This effect of hIGF-I occurred without any significant changes in pituitary GH, AVP, oxytocin, blood glucose or bone growth over this short-term infusion, nor was there any obvious effect on spontaneous GH secretion, monitored over the entire infusion period. We conclude that the diabetic rat is not a good model to study growth stimulation by short-term insulin or IGF-I treatments because the insulin-like effects of these peptides obscure their specific growth-promoting activities in this model.
 ...
PMID:Growth hormone and growth in diabetic rats: effects of insulin and insulin-like growth factor-I infusions. 268

There are indications that ovarian oxytocin is involved in luteolysis and the endometrium may play a key role for the events of luteolysis. A certain priming period with progesterone is a prerequisite for the induction of luteolysis. Treatment of heifers with progesterone for 4 days beginning after the LH surge shortens the oestrous cycle length significantly. Besides an involvement in luteolysis, there are indications for an intraovarian function of oxytocin influencing steroidogenesis by inhibition of progesterone secretion. Growth factors have been identified in ovarian tissue and insulin-like growth factor-I has a very potent effect on bovine granulosa cell function. Growth factors may be involved in the growth and differentiation of follicles.
 ...
PMID:Ovarian peptides in the cow and sheep. 268 39

The effect of insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF), fibroblast growth factor (FGF) and nerve growth factor (NGF) on production of oxytocin and progesterone by cultured bovine granulosa and luteal cells was studied. Secretion of oxytocin was stimulated, in a dose-dependent manner, by IGF-I at 48 and 120 h of culture to levels much higher than those after stimulation with LH, FSH, EGF, FGF or NGF. A similar effect of IGF-I was observed for progesterone but, in contrast to oxytocin, secretion of progesterone was not increased by EGF, NGF or FGF. During primary culture, for 4 h, of dispersed bovine luteal cells obtained from corpora lutea between days 4 and 10 of the oestrous cycle, all the growth factors tested failed to stimulate secretion of oxytocin or progesterone. The data suggest the relevance of growth factors (especially IGF-I) for ovarian physiology and their possible importance for differentiation of follicles and luteinization.
 ...
PMID:Insulin-like growth factor-I stimulates oxytocin and progesterone production by bovine granulosa cells in culture. 325 17

Prostaglandin F2 alpha (PGF2 alpha)-induced release of ovarian oxytocin was investigated to determine whether the effect in vivo was local. [3H]PGF2 alpha infused downstream into a single ovarian lymphatic was transferred into the adjacent ovarian vasculature (estimated transfer 1.1 and 1.7%, two experiments). When unlabelled PGF2 alpha was infused in a similar manner (76 pmol min-1), there was a prompt eightfold increase in ovarian oxytocin release from the adjacent ovary containing a corpus luteum, but no effect on the opposite corpus luteum, showing that the effect was local. Instillation of 2% lignocaine into the ovarian vascular pedicle did not affect PGF2 alpha-induced oxytocin release, supporting the idea that neural mechanisms are not involved. Repeated doses of PGF2 alpha given close-arterially produced a successive reduction in oxytocin release. This effect was prevented by a prior infusion of insulin-like growth factor-I (IGF-I), which itself gave a small, but significant, increase in oxytocin release. The results show that PGF2 alpha in ovarian lymphatics acts locally and directly to stimulate ovarian oxytocin secretion, that repeated exposure of the corpus luteum to pulses of PGF2 alpha can result in tachyphylaxis, and that this latter effect can be ameliorated by IGF-I infused in vivo.
 ...
PMID:Unilateral control of ovarian oxytocin release and the facilitatory effects of insulin-like growth factor-I in sheep. 802 85

The aim of the present experiments was to examine the effects of oxytocin (1-10 000 ng/ml) on hormone and cyclic nucleotide secretion by human granulosa cells cultured in a serum-supplemented medium. The release of progesterone, oestradiol, insulin-like growth factor-I, prostaglandin F2alpha, cAMP and cGMP into the incubation medium was analysed by radioimmunoassay. An inhibition of progesterone, but not of oestradiol release was observed. Oxytocin also stimulated insulin-like growth factor-I, prostaglandin F2alpha, cAMP and cGMP output. The results suggest an involvement of oxytocin in the autocrine/paracrine regulation of steroid, insulin-like growth factor, prostaglandin and cyclic nucleotide release by human ovarian cells.
 ...
PMID:Oxytocin affects the release of steroids, insulin-like growth factor-I, prostaglandin F2alpha and cyclic nucleotides by human granulosa cells in vitro. 867 Nov 78

The aim of the present experiments was to demonstrate the release of insulin-like growth factor-I (IGF-I) by human granulosa cells, and to examine the role of growth hormone (GH), oxytocin, steroids and cAMP-dependent intracellular mechanism in its control. A significant accumulation of IGF-I in a serum-supplemented medium in which the human granulosa cells were cultured for 4 days was observed. The concentration of IGF-I in the medium was particularly high at 3 and 4 days of culture. The addition of GH (1-10,000 ng/ml) to the medium increased IGF-I secretion by the cells. A higher GH dose (100,000 ng/ml) was inhibitory. Oxytocin stimulated IGF-I release at doses of 10-10,000 ng/ml. Dibutyryl-cAMP, isobutyl-methyl-xanthine (inhibitor of cAMP catabolism) or forskolin (stimulator of cAMP production) inhibited IGF-I output at these doses. Additions of progesterone (1-1,000 ng/ml) did not affect IGF-I release, whilst adrostenedione and estradiol were stimulatory at doses of 1, 10, 100, 1,000 ng/ml and 10, 100 and 1,000 ng/ml respectively. Testosterone inhibited IGF-I at a dose of 1,000 ng/ml but not at lower doses (1, 10 or 100 ng/ml). Blockade of estradiol (but not of testosterone) in the medium by specific antisera (1 or 10%) significantly reduced IGF-I output. The same effect was observed with an antiserum to progesterone when added at 0.1%, whilst higher doses (1 or 10%) stimulated IGF-I secretion. The present observations demonstrate the involvement of peptide, steroid hormones and cAMP in the regulation of IGF-I secretion by luteinized human granulosa cells. In particular, both GH and oxytocin are stimulators of IGF-I release. Estradiol and androstenedione, but not testosterone, may also be stimulators of IGF-I output. The involvement of progesterone in this process can also not be excluded. A cAMP-dependent intracellular mechanism appears to play an inhibitory role in the regulation of IGF-I secretion by luteinized human granulosa cells.
 ...
PMID:The release of insulin-like growth factor-I by luteinized human granulosa cells in vitro: regulation by growth hormone, oxytocin, steroids and cAMP-dependent intracellular mechanisms. 878 8

Although milk yield of cows and goats is known to be closely related to the total flow of blood through the udder, a number of studies suggest that milk yield can vary independently. No studies have attempted to measure the proportion of total flow that is nutritive. Within the mammary gland, capillary networks form a basket-like architecture surrounding each alveolus. Notably, flow in individual capillaries is not constant and varies among capillaries. Capillary flow (measured by intravital microscopy) was decreased by oxytocin, which generally increased total flow in the mammary artery, suggesting that the proportion of total flow that is nutritive can vary. In addition to classic metabolic regulators (e.g., carbon dioxide and oxygen) of tissue blood flow, the mammary gland produces a number of vasodilatory compounds, including parathyroid hormone-related protein, insulin-like growth factor-I, prostacyclin, nitric oxide, and endothelin. All of these compounds have been shown to alter mammary blood flow. Mammary tissue also contains kallikrein and angiotensin-converting enzyme, which convert circulating kinins and angiotensin, respectively, into potent vasoactive compounds. A number of these compounds are produced by epithelial cells themselves, providing a mechanism for the functioning epithelium to control its own blood supply and, hence, nutrient flow for milk synthesis. In this review, we examine the nature of the mammary microcirculation, its behavior under different conditions, and some of the regulatory features of the mammary microvasculature.
 ...
PMID:Regulation of blood flow in the mammary microvasculature. 887 13


1 2 Next >>