Plasma oxytocin

Modahl, C., Green, L., Fein, D., Morris, M., Waterhouse, L., Fein-stein, C., and Levin, H. (1998) Plasma oxytocin levels in autistic children. Biol Psychiatry 43 270-277. 

Turner, R.A., Altemus, M., Enos, T, Cooper, B., and McGuinness, T. (1999) Preliminary research on plasma oxytocin in normal cy-... 

Plasma oxytocin has been shown to be reduced in autistic children and moreover, levels of oxytocin were correlated with social impairment (Modahl et al., 1998). A follow-up study using the same subjects found that the autistic children had higher levels of the precursor of oxytocin when compared with controls, suggesting that reduced plasma oxytocin in autistic children may be related to how oxytocin is processed (Green et al., 2001). Preliminary studies have demonstrated that infusion with oxytocin can reduce repetitive behaviors such as... 

Dawood, M.Y. Ylikorkala, O. Fuchs, F. Plasma oxytocin levels and disappearance rate after buccal pitocin. Am. J. 

Plasma oxytocin concentrations in men, nonpregnant women, and pregnant women before and during spontaneous labor. J Clin Endocrinol Metab 1981 53 730-3. 

Oxytocin is metabolized by oxytocinase, which is produced by the placenta and appears to regulate uterine oxytocin. Oxytocinase does not appear to affect plasma oxytocin, which is metabolized by the liver and kidney. 

It is well established that the concentration of oxytocin in plasma is increased in a pulsatile manner prior to, and during, parturition in a wide... 

The IC50 is similar to AD50 or ID50 experiments, except that plasma concentration of the antagonist is measured during the experiment and the potency is expressed as the plasma concentration of the antagonist causing 50% inhibition of the oxytocin response. 

Similarly, though plasma protein binding data were not ostensibly used in the identification of an oxytocin antagonist suitable for advancement to the clinic, such data were used to explain the differences between in vivo and in vitro potency [46]. 

Uvnas-Moberg, K., Windstrom, A. M., Nissen, E., and Bjorvell, H. 1990. Personality traits in women 4 days post partum and their correlation with plasma levels of oxytocin and prolactin. Journal of Psychosomatic Obstetrics and Gynaecology 11 261—272. 

Plasma prolactin levels are reduced with acute treatment and remain suppressed after 28 days of chronic treatment (Murphy et al. 1998). With acute treatment, no effects are seen on plasma luteinizing hormone or testosterone levels. However, chronic dietary 5% ginseng increases testosterone levels in male rats (Fahim et al. 1982). Chronic ginsenosides do not alter posterior pituitary hormones oxytocin and vasopressin (Zierer 1991). Similarly, human males administered ginseng extract showed an increase in plasma testosterone, dihydrotestosterone, follicle-stimulating hormone, and luteinizing hormone, but a decrease in prolactin (Salvati et al. 1996). 

These messengers also play a role in regulating contraction of myometrium, which consists of smooth muscle fibres. Contraction is controlled by increases in the concentration of cytosolic Ca ions. Prostaglandins activate Ca ion channels in the plasma membrane of the fibres oxytocin activates release of Ca from intracellular stores. The increase in concentration of Ca ions leads to activation of myosin light-chain kinase which leads to crossbridge cycling and contraction (as described in Chapter 22 Figure 22.12). 

Oxytocin (Pitocin, Syntocinon) is a cyclic 8-amino acid peptide that is synthesized in the paraventricular nucleus of the hypothalamus and transported within hypothalamic neurons (in association with neurophysin) to the posterior pituitary for storage. Its mechanism of action involves the direct stimulation of oxytocin receptors found on the myometrial cells. Oxytocin circulates unbound in the plasma, where it has a half-Ufe of approximately 15 minutes. It is primarily inactivated in the kidneys and liver. 

Oxytocin, a nine amino acid peptide, is synthesized primarily in the paraventricular and supraoptic (SON) nuclei of the hypothalamus, from which it is released to the general circulation through the posterior pituitary (Insel et ah, 1997). However, oxytocinergic fibers have also been found to project from the PVN to the limbic system and several autonomic centers in the brain stem. This central OT pool appears to be independent of pituitary OT release cerebrospinal fluid (CSF) and plasma OT responses to numerous stimuli are not correlated (Insel, 1997). Oxytocin and its analog (or partner) peptide vasopressin are found only in mammals. A related peptide, vasotocin, thought to be the evolutionary precedent of these peptides, is found in reptiles and birds. The first known actions of OT were its peripheral effects on the physiology of new mothers. In mammals, OT stimulates milk ejection and uterine contraction, essential aspects of maternal physiology (Insel et ah, 1997). 

Oxytocin is administered intravenously for initiation and augmentation of labor. It also can be administered intramuscularly for control of postpartum bleeding. Oxytocin is not bound to plasma proteins and is eliminated by the kidneys and liver, with a circulating half-life of 5 minutes. 

A mucoadhesive buccal patch was evaluated for transmucosal delivery of oxytocin (OT) [103], OT was incorporated with coformulations of Carbopol 974P and silicone polymer. The plasma concentrations of OT remained 20- to 28-fold greater than levels obtained from placebo patches for a period of 0.5 to 3.0 h. 

Cameron JL, Pomerantz SM, Layden LM, Amico JA (1992) Dopaminergic stimulation of oxytocin concentrations in the plasma of male and female monkeys by apomorphine and a D2 receptor agonist. J Clin Endocrinol Metab 75 855-860. 

Melis MR, Argiolas A, Stancampiano R, Gessa GL (1990) Effect of apomorphine on oxytocin concentrations in different brain areas and plasma of male rats. Eur J Pharmacol 752 101-107. 

B.K. Matuszewski, C.M. Chavez-Eng, M.L. ConstsmzeT, Development of LC-MS-AdS methods for the determination of a new oxytocin receptor antagonist (L-368,899) extracted from human plasma and urine a case of lack of specificity due to the presence of metabolites, J. Chromatogr. B, 716 (1998) 195. 

Numerous immunoassays for measuring oxytocin in plasma or urme have been described. However, their routine clinical application has been limited because of a lack of physiological relevance to human reproductive disorders and because of a lack of easy-to-use immunoassays with acceptable sensitivity and specificity. With most plasma assays, a preliminary extraction procedure with column chromatography is required, not only to concentrate the minute amount of hormone that is present in the specimen, but also to remove nonspecific interfering substances. 

Blood specimens for oxytocin are collected into prechilled tubes containing EDTA as an anticoagulant. Most procedures recommend that specimens be delivered to the laboratory on ice and centrifuged at 4 °C within 30 minutes of collection. The plasma is then removed and stored frozen at -20 °C until analysis is performed. Random urine specimens are collected without preservatives alternatively, complete 24-hour urine specimens may be collected in lOmL of 6mol/L hydrochloric acid. Significant deterioration of both hormones occurs with prolonged storage. 

Oxytocin values are quantified relative to the bioassay potency of a synthetic reference preparation. Plasma results are reported as microunits per milliliter (1 fiU is equivalent to 2pg of synthetic oxytocin) ... 

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