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

Lactating cattle were used to validate a transit time ultrasonic blood flow metering system for measuring mammary gland arterial blood flow. Blood flow probes were surgically placed around the right external pudic artery. An electromagnetic flow probe was implanted in tandem with the ultrasonic probe in two cows for comparative measurements. The absolute accuracy of the implanted flow probes was assessed in vivo by mechanical means on anesthetized cows after 2 to 3 wk of implantation. The zero offset of the ultrasonic probes ranged from -12 to 8 ml/min. When the ultrasonic probe was properly implanted, the slopes of the calibration curves were linear and ranged from .92 to .95, tracking absolute flow to within 8%. The transit time instrument's performance was examined under a variety of physiological conditions. These included milking and hormone injections. The transit time ultrasonic flow meter accurately measured physiological changes in mammary arterial blood flow in chronically prepared conscious cattle. Blood flow increased 29% during milking. Epinephrine decreased mammary blood flow by 90 to 95%. Oxytocin doses increased mammary blood flow by 15 to 24%.
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PMID:Measuring bovine mammary gland blood flow using a transit time ultrasonic flow probe. 267 32

Experiments were designed to study the effects of catecholamines on oxytocin responses and milk removal in dairy cows. Adrenalin, noradrenalin, dopamine, isoproterenol (a beta-adrenoceptor agonist), phentolamine (an alpha-adrenergic blocker) and propranolol (a beta-adrenergic blocker) were infused intravenously. In addition, adrenalin was infused together with phentolamine and/or propranolol. Infusions started 8 min before milking and lasted until the end of milking. In some cases electroshocks (for 5 s) were applied immediately before milking in the absence and presence of phentolamine and propranolol. Adrenalin, noradrenalin and dopamine reduced milk removal, but only if administered in supraphysiological amounts. The effect of adrenalin and electroshocks on milk removal could be inhibited only partly by phentolamine. Inhibition of milk removal was not mediated by reduced oxytocin responses. Enhanced local release of catecholamines from sympathetic nerves was presumably responsible for lowered milk removal in response to electroshocks. Milk removal was facilitated during alpha-adrenergic blockade and during beta-adrenoceptor stimulation.
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PMID:Catecholamines, oxytocin and milk removal in dairy cows. 276 Feb 95

We examined the effects of several in vitro experimental systems on the apparent potencies of putative secretagogues for stimulating ACTH release from rat anterior pituitary cells. Cells were prepared by trypsin digestion and gentle mechanical dispersion. Aliquots of the same cell preparations were tested in 1) a microperifusion system immediately after dispersion (day 0), 2) the same microperifusion system after 4 days of static suspension culture on a layer of Sephadex G-10 gel particles (day 4), 3) a static suspension system after 4 days of static suspension culture, and 4) a static monolayer system after 4 days of monolayer culture. Ovine CRF stimulated release of similar amounts of ACTH in all of the systems on days 0 and 4, except in one experiment, in which the response was less on day 4. Arginine vasopressin (AVP), oxytocin, and angiotensin II all appeared to be more potent in day 4 than in day 0 cells in the perifusion system, and the synergism of AVP with ovine CRF was also increased. Dioctanoylglycerol, which directly activates protein kinase-C, and forskolin, which directly activates adenylate cyclase, both stimulated greater release in day 4 cells. The mechanism(s) responsible for the difference in the responses of day 0 and day 4 cells is unknown. Epinephrine had only a small effect in the microperifusion system, but both epinephrine and norepinephrine had potencies comparable to AVP in the static suspension and monolayer systems. This was not due to prolonged exposure to the catecholamines, suggesting that these agents may act on other anterior pituitary cells to release metabolic products that secondarily stimulate the corticotrophs to release ACTH. The same situation appears to be true for atrial natriuretic factor. Gastrin-releasing peptide, its bioactive COOH-terminal half, which was active in a rat urinary bladder smooth muscle assay, its amphibian analog, bombesin, and cholecystokinin (26-33) were devoid of ACTH-releasing activity in all of the systems, in contrast to the findings of others. Since 4-day culture of dispersed cells improved most of their responses and diminished none, we postulate that they may more closely resemble normal pituitary cells in function, and since cellular metabolites are unlikely to accumulate in the interstitial fluid of the pituitary gland, we propose that the secretory functions of cells in perifusion systems may more closely resemble those in the pituitary gland in situ than they do in static incubation systems.
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PMID:Effects of several in vitro systems on the potencies of putative adrenocorticotropin secretagogues on rat anterior pituitary cells. 283 88

Carp (Cyprinus carpio) liver maintained normal glycogen content and enzyme complement for several days in organ culture. Epinephrine-stimulated glycogenolysis, phosphorylase activation, and cyclic AMP (cAMP) accumulation in a concentration-dependent manner with EC50s of 100, 100, and 500 nM, respectively. These actions were blocked by the beta-adrenergic antagonist, propranolol, but not by the alpha-adrenergic antagonist phentolamine. Glycogenolysis and tissue cAMP were uninfluenced by 10(-6) M arginine vasotocin, arginine vasopressin, lysine vasotocin, lysine vasopressin, mesotocin, or oxytocin, but were slightly increased by 10(-5) M isotocin and slightly decreased by 10(-6) M angiotensin II. [125I]-iodocyanopindolol (ICP), a beta-adrenergic ligand, bound to isolated carp liver membranes with a KD of 83 pM. Maximum binding of 45 fmol/mg protein was at 600 pM. Propranolol, isoprenaline, epinephrine, phenylephrine, norepinephrine, and phenoxybenzamine displaced ICP with KDs of 100 nM, 2, 20, 20, 60, and 200 microM, respectively. The alpha-adrenergic antagonists, yohimbine and prazosin, showed no specific binding. These data provide evidence that catecholamines act via beta-adrenergic receptors in carp liver and that alpha-adrenergic receptors are not present. Vasoactive peptides play no significant role in regulation of carp liver glycogenolysis.
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PMID:Hormonal regulation of hepatic glycogenolysis in the carp, Cyprinus carpio. 303 3

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

A case of an allergic reaction to synthetic oxytocin administered during cesarean section is reported. Epinephrine was more effective in improving the severe hypotension than ephedrine. The incidence of anaphylactoid reaction to oxytocin is very low, but this potential problem must always be kept in mind in daily obstetric practice.
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PMID:Anaphylactoid reaction to oxytocin during cesarean section. 340 36

The concentrations of immunoreactive oxytocin and arginine vasopressin (AVP) and their respective neurophysins (NpI and NpII) were compared in bovine adrenal cortex and medulla. While the concentration of AVP was similar in both tissues there was more NpII in the medulla. The medulla also contained much more oxytocin and NpI than the cortex. The extracted AVP and oxytocin had identical retention times to those of the synthetic peptides on high-performance liquid chromatography (HPLC) and were biologically active in assays for antidiuretic and milk-ejection activity (with potencies of 310 units/mg and 340 units/mg respectively). Adrenal NpI and NpII behaved identically to commercially available neurohypophysial proteins on HPLC. Oxytocin, NpI and AVP were assayed in five subcellular fractions of bovine adrenal medulla prepared on discontinuous sucrose gradients. A high proportion of each co-localized with noradrenaline and adrenaline in the chromaffin granule fraction. Binding of [3H]AVP and [3H]oxytocin to crude bovine adrenal medulla membranes was dependent upon both time and temperature. The binding sites were specific and saturable: studies with the V1 AVP antagonist d(CH2)5Tyr(Me)AVP and the V2 agonist 1-deamino-8-D-AVP indicated that the AVP receptor was V1 in specificity. Scatchard plots showed that each ligand interacted with a single high-affinity, low-capacity binding site: oxytocin dissociation constant (Kd) 3.1 +/- 0.29 nmol/l, maximum binding capacity (Bmax) 89.6 +/- 18.4 fmol/mg protein (n = 3); AVP Kd 0.73 +/- 0.02 nmol/l, Bmax 26.5 +/- 8.3 fmol/mg protein (n = 3).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Arginine vasopressin and oxytocin in the bovine adrenal gland. 366 43

A modification of the rat isolated seminal vesicle preparation is described, emphasizing the necessity to use younger animals (40-50 days old and weighing between 125 and 150 g) and to expel thoroughly all vesicular contents. Under the experimental conditions used (tissues suspended under a resting tension of 350 mg in a continuous flow of a modified Krebs solution run at the rate of 15 ml/min, maintained at 32 degrees C, and bubbled with 5% CO2 in O2), the preparation was quite sensitive, but only to a few selected agonists, and remained viable for over 4-6 hr. Adrenaline, noradrenaline, dopamine, and acetylcholine all produced concentration-dependent and reproducible contractions. However, histaminergic, serotoninergic, purinergic, and opioid agonists were inactive as were prostaglandins of the E and F series and the polypeptides angiotensin, vasopressin, and oxytocin. In general, the tissue was rather insensitive to relaxant drugs, with only papaverine and sodium nitrite producing some relaxation in tissues previously contracted by carbachol. Advantages of the preparation include marked responsiveness, but only to a few selected agonists, and suitability for use as a paired tissue. It is suggested that employed under suitable experimental conditions, the preparation deserves a more frequent consideration for use during pharmacological investigations concerned with postsynaptic aspects of noradrenergic or cholinergic transmission.
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PMID:Pharmacological evaluation of the isolated rat seminal vesicle preparation. 395 Dec 38

Literature on the effects of hormones on human myometrial activity is reviewed. The effects of estrogens, gestagens, and prostaglandins on myometrial activity in pregnant and nonpregnant women, and those of maternal and fetal corticosteroids, biogenic amines, and oxytocin and vasopressin are discussed. Estrogens produce small, frequent, local, and nonpropagated contractions of the myometrium, while gestagens produce contractions of higher amplitude, longer duration, and lower frequency. Maternal and fetal corticosteroids have some importance for myometrial activity of pregnancy in some animals, but their role in humans remains obscure. Epinephrine and norepinephrine stimulate myometrial activity in humans, though their physiologic and therapeutic importance is doubtful. The same holds for serotonin. Oxytocin in large doses stimulates myometrial activity during the proliferative stage of the cycle, but is without effect in smaller doses. During pregnancy, oxytocin progressively stimulates myometrial activity, particularly toward the end of pregnancy. Oxytocin is often used to initiate and stimulate labor. Vasopressin, on the other hand, stimulates myometrial activity during the secretory phase of the cycle, especially around the onset of menstruation. Vasopressin has a less marked effect during pregnancy than oxytocin, and its effects are not enhanced as pregnancy comes to term. The fetus is known to produce considerable amounts of oxytocin and vasopressin during labor, though the significance of this contribution remains to be elucidated. Prostaglandins have a potent stimulatory effect on myometrial activity in both pregnant and nonpregnant women. The possibility that prostaglandins play a physiologic role in the onset of myometrial activity remains to be determined.
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PMID:Hormonal effects on human myometrial activity. 462 Mar 76

Rhythmic motility of teats in lactating cows in vivo was studied by an improved plethysmographic technique. Oxytocin was infused intravenously and drugs were injected into the artery of the filled udder. The beta-adrenergic agent, isoprenaline, induced relaxation of the teats whereas the alpha-adrenergic agents phenylephrine and noradrenaline, elicited contraction. In one animal however, noradrenaline always exerted a biphasic effect. Pre-treatment with propranolol, a beta-adrenergic blocking agent, changed the biphasic effect into a purely activating response. Adrenaline, which exhibits both alpha and beta effects, induced relaxation, but after propranolol treatment relaxation was abolished and even converted into contraction of the teat. It seems clear that both alpha and beta adrenoceptors are present in longitudinal smooth muscles of the teats. Milk losses as intermittent spurts were observed in several cows. Spurts occurred synchronously with rhythmical teat motility in the filled udder during oxytocin infusion. The intensity of milk leakage was increased by isoprenaline and inhibited by noradrenaline, indicating the presence of alpha and beta receptors in teat sphincter muscles. Starting and stopping of milk spurts in correlation with rhythmical teat contractions were studied by audiovisual synchronization of video recording tape. The most common type of spurt began near the middle of the teat's relaxation phase and ended either just before or exactly at the beginning of the contraction phase. Interruption of the spurt is primarily due to closure of the streak canal.
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PMID:Studies on the motility of smooth muscles of the teats in lactating cows. 625 18


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