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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine granulosa cells were cultured in a defined serum-free system to examine their responsiveness to acetylcholine (ACh). Continuous exposure to concentrations of ACh between 10(-8)-10(-4) M resulted in dose-dependent increases (up to 6.7-fold) in the secretion of oxytocin and progesterone, with an ED50 of 6.6 microM. Ascorbic acid (0.5 mM), a known stimulator of granulosa secretion, synergized with ACh, resulting in an increase in the amounts of hormone secreted and a 7-fold increase in cellular sensitivity to ACh (ED50 = approximately 0.9 microM). Treatment of cells with ACh for 24 h at various times during a typical 5-day culture resulted in a stimulation that persisted for up to 4 days after removal of ACh. Carbachol (10(-8)-10(-4) M), a receptor antagonist with both antimuscarinic and antinicotinic actions, had no distinct effect on hormone secretion by the cells, but the effects of 10(-5) M ACh could be completely abolished by equimolar or hypomolar concentrations of the specific muscarinic receptor antagonists atropine and scopolamine. Nicotine bitratrate (10(-8)-10(4) M), a dose-dependent nicotinic receptor agonist/antagonist, had no effect on the cells. It is concluded that bovine granulosa cells, exhibiting a luteinized phenotype in culture, are responsive to cholinergic agonists in a specific and saturable manner. The response of the cells is probably mediated through muscarinic receptors and has both medium and long term (persistent) components. These results indicate that cholinergic neurotransmitters may play a direct role in the regulation of ovarian function in the ruminant.
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PMID:Cholinergic stimulation, through muscarinic receptors, of oxytocin and progesterone secretion from bovine granulosa cells undergoing spontaneous luteinization in serum-free culture. 229 62

Bovine granulosa cells secrete oxytocin when cultured in a serum-supplemented medium. The time-course of secretion is similar to that in the early corpus luteum in vivo, with a delay of 1 to 2 days followed by a peak and decline over the first 5 days of culture. We have investigated the basis of this time-course in vitro and studied the temporal characteristics of the stimulatory actions of ascorbic acid and adrenaline on this process. Cells cultured on stirred microcarriers showed a similar pattern of secretion of oxytocin to those cultured on conventional flat plates, despite continuing and rapid mitosis. This indicated that the secretion profile in conventional culture was not an artifact related to the cessation of mitosis. Furthermore, secretion of oxytocin and progesterone by cells on microcarriers was stimulated without a corresponding change in mitotic rate, showing that the secretion per cell had been increased. In conventional culture, addition of ascorbic acid to culture media (0.5 mmol/l) increased the secretion of oxytocin (up to 4.5-fold) but only if ascorbic acid was present during the first day of culture. The cells showed a progressive refractoriness to stimulation after 12 h. Since the time-course of secretion was unaltered by treatment, this resulted in a delay of 1 to 2 days before the action of the ascorbate was seen. The secretion of progesterone was similarly affected but with less stimulation and less consistency. In contrast, cells treated with adrenaline (10 mumol/l) secreted more oxytocin on the day of treatment and did so at any time during culture provided that there was sufficient basal secretion of hormone. Adrenaline also failed to alter the time-course of secretion but treated cells showed a persistent response, maintaining enhanced secretion for up to 3 days after the adrenaline had been removed. Ascorbate and adrenaline were highly synergistic in their effects, provided that the ascorbate was present from the start of culture; the response to adrenaline strongly reflected the degree of ascorbate stimulation. We conclude that granulosa cells secrete oxytocin according to an inherent time-schedule and that there is a limited period during which they can respond to ascorbate. Since ascorbate is required for the biosynthesis of oxytocin, this suggests that the availability of ascorbate during corpus luteum formation may determine the amount of oxytocin which can be released subsequently in response to catecholamines.
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PMID:The time-course of oxytocin secretion from cultured bovine granulosa cells, stimulated by ascorbate and catecholamines. 335 20

The effects of catecholamines and ascorbic acid on cultured bovine granulosa cells have been examined to assess their possible role in the initiation and maintenance of luteal oxytocin secretion. The actions of these agents have also been compared with the previously reported ability of follicular theca tissue to enhance oxytocin secretion. Using granulosa cells cultured in serum-supplemented medium, we observed a highly significant enhancement of oxytocin secretion in the presence of adrenaline and noradrenaline, particularly over the concentration range 1-10 mumol/l. This effect was accompanied by smaller and less consistent changes in progesterone secretion and did not involve any change in the time-course of oxytocin secretion. Acetylcholine was without effect. Ascorbic acid stimulated oxytocin secretion when used alone over a range of concentrations, but was also able to synergize with adrenaline. Lactic acid was ineffective. The stimulation of oxytocin secretion by adrenaline could be blocked by equimolar propranolol, but the stimulation of progesterone was not blocked. Propranolol had a variable effect on the ability of theca tissue to stimulate oxytocin secretion by granulosa cells but the results also suggested the presence of some beta-agonistic activity in the culture medium. We conclude, first, that catecholamines may be involved in the regulation of ovarian oxytocin secretion, secondly, that ascorbate may regulate oxytocin secretion through its involvement in the biosynthesis of oxytocin but also through interaction with catecholamines and, thirdly, that the stimulatory action of theca tissue probably does not involve the action of beta-agonists.
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PMID:Catecholamines and ascorbic acid as stimulators of bovine ovarian oxytocin secretion. 366 32

To determine if there are inter-relationships between progesterone, oxytocin (OT), dopamine (DA), noradrenaline (NA) and ascorbic acid, these compounds were measured in the corpus luteum (CL) from cattle at different stages of the oestrous cycle (n = 42) and from 1-5 months of pregnancy (n = 27). They were measured by radioimmunoassay (RIA), high performance liquid chromatography (HPLC) and colorimetric methods. Corpora lutea were collected from heifers and cows within 30 min of slaughter on days 1-5, 6-10, 11-16 and 17-21 of the oestrous cycle. The stage of pregnancy was determined on the basis of foetal size and development. Each CL was divided into four parts and stored in liquid nitrogen. For hormone estimation, the tissue was homogenised/powdered and suspended in phosphate buffer (for OT and progesterone), 0.1 M trichloracetic acid (TCA; for catecholamines) or in ice-cold metaphosphoric acid (for ascorbic acid). There were no significant differences in the measured parameters between cows and heifers, and so the data were combined. The concentration of DA was correlated with NA (r = 0.66; P < 0.001) during the oestrous cycle and was highest in newly formed CL (P < 0.01) as compared with early CL, regressed CL and CL of pregnant females. NA was negatively correlated (P < 0.01) with progesterone (r = -0.53) and OT (r = -0.41). In contrast, progesterone and OT were positively correlated with each other (r = 0.81; P < 0.01) during all stages of the oestrous cycle, but not during pregnancy. The lowest concentrations of ascorbic acid were observed in regressed CL. Ascorbic acid concentrations were correlated (P < 0.01) with those of progesterone (r = 0.68), OT (r = 0.42) and DA (r = -0.37). Luteal concentrations of ascorbic acid, progesterone and OT followed a pattern consistent with the development and regression of the CL. Luteal concentrations of catecholamines were not consistent with this pattern.
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PMID:Concentrations of catecholamines, ascorbic acid, progesterone and oxytocin in the corpora lutea of cyclic and pregnant cattle. 1049 56