Vasopressin Concentration (vasopressin + concentration)

Distribution by Scientific Domains

Selected Abstracts

Plasma Vasopressin Concentrations and Fos Protein Expression in the Supraoptic Nucleus Following Osmotic Stimulation or Hypovolaemia in the Ovariectomized Rat: Effect of Oestradiol Replacement

D. E. Hartley
Abstract The set points for vasopressin release in response to increasing plasma osmolality and hypovolaemia alter with reproductive status. Here, we studied stimulated vasopressin release following ovariectomy and oestrogen replacement, neuronal activity being measured in terms of immediate early gene expression. Observations were carried out on three groups of female Sprague-Dawley rats. The first group were ovariectomized. The second group were given a subcutaneous oestrogen implant (20 g/ml oestradiol-17,) at the time of ovariectomy. The final group were left intact and observations performed at oestrus. Two weeks after ovariectomy, vascular cannulae were implanted under anaesthesia and at least 48 h allowed for recovery before hormone release was stimulated by infusion of 1.5 m NaCl for 90 min, or hypovolaemia induced by the removal of 10 mg/kg body weight taken in 1-ml aliquots. Blood pressure was monitored, and blood samples were taken for determination of packed cell volume and plasma vasopressin and osmolality. After a minimum of 48 h, the challenge was repeated, the rats anaesthetized, and perfused with 4% paraformaldehyde. Brain sections were processed for immunocytochemical detection of Fos protein. Vasopressin release in response to both stimuli was reduced in ovariectomized compared to intact rats and the response could be substantially restored by oestradiol replacement. The number of Fos positive cells in the supraoptic nucleus of oestrogen-replaced rats was significantly higher than in the ovariectomized group and not statistically different from the intact group. [source]

Renal Response to Arginine Vasopressin During the Oestrous Cycle in the Rat: Comparison of Glucose and Saline Infusion Using Physiological Doses of Vasopressin

David E. Hartley
The renal response to arginine vasopressin in the rat has been shown to depend on reproductive status. However there is no consensus as to when the kidney is most responsive. The varying results could depend on the protocol and the dose of hormone used. A study has been performed, with physiological doses of vasopressin, comparing the responses during infusion of hypotonic saline and glucose. After an equilibration period of 150 min, conscious rats were infused on each of the four days of the oestrous cycle with either isotonic saline (0.077 M) or 0.14 M glucose for a control period of 45 min. Vasopressin was then infused at 10-40 fmol min,1 for 1 h, followed by a recovery period of 90 min. Timed urine samples were collected for determination of volume, sodium concentration and osmolality. During the control period urine flow was greatest at oestrus and dioestrus day 2 and sodium excretion on dioestrus day 2 irrespective of the infusate. Vasopressin concentrations achieved lay within the physiological range and no difference was observed between the different days for a given dose. Infusion of vasopressin in both saline and glucose produced a dose-dependent antidiuresis, the greatest responses being seen of pro-oestrus and dioestrus day 2. It was only with the highest rate of infusion that a significant increase in sodium excretion was seen on each day of the cycle and the greatest responses were seen on pro-oestrus and dioestrus day 1 for both infusates. Thus the kidney shows the greatest response to physiological doses of vasopressin at pro-oestrus and dioestrus day 1 irrespective of the infusate employed. [source]

Vasopressin in the treatment of vasodilatory shock in children

Satoshi Masutani
Abstract,Background:,Many recent studies suggest that vasopressin deficiency is an important cause of catecholamine-resistant hypotension with vasodilation in adults, but little is known about vasopressin deficiency in children. Methods:,To clarify the usefulness of vasopressin administration in pediatric cathecolamine-resistant hypotension with preserved ventricular contractility, urinary output and blood pressure response to vasopressin were retrospectively analyzed in 12 consecutive patients (15 instances) who were treated with vasopressin. The causes of vasodilation were central nervous system disturbance (n = 5), side-effect of drug (n = 5), and infection (n = 5). Plasma vasopressin concentration was measured six times before vasopressin administration and five times during vasopressin administration. Results:,Patients were divided into four groups according to their response to vasopressin administration. In group 1 (n = 5), urinary output increased to > 3 mL/kg per h within 3 h after vasopressin administration. In group 2 (n = 4), urinary output increased to > 3 mL/kg per h from 3 to 5 h after vasopressin administration. In group 3 (n = 4), urinary output did not increase to > 3 mL/kg per min within 5 h after vasopressin administration, but systolic blood pressure increased to > 120% of the level at the time of vasopressin administration. All remaining patients were classified into group 4 (n = 3). Plasma vasopressin concentration were low considering the markedly hypotensive state in all six instances. Plasma vasopressin concentration during vasopressin administration were significantly increased compared with before administration (P < 0.05). No apparent side-effects were observed in this series. Conclusion:,Vasopressin deficiency may occur in catecholamine-resistant hypotension of pediatric patients due to various causes including central nervous system disturbance, drug induced hypotension and sepsis. Small doses of vasopressin administration seems to be very effective in such conditions by increasing blood pressure and urinary output. [source]

The role of arginine vasopressin in human labour: functional studies, fetal production and localisation of V1a receptor mRNA

S. Thornton
Objective To investigate labour-associated changes in: 1. the myometrial contractile response to arginine vasopressin compared with oxytocin in vitro 2. fetal production of arginine vasopressin and 3. myometrial vasopressin V1a receptor mRNA. Design The contractile response to vasopressin (compared with oxytocin) was investigated in paired myometrial strips in vitro. Blood was taken from the umbilical artery and vein at delivery and arginine vasopressin measured by radio-immunoassay. V1a receptor mRNA was determined by in situ hybridisation. Results Myometrium was more sensitive to arginine vasopressin than oxytocin (P <0.05 for frequency, amplitude and activity integral in paired strips) after, but not before labour. There was a marked umbilical arteriovenous difference in arginine vasopressin concentration at delivery suggesting fetal production which was not influenced by labour. Myometrial vasopressin V1a receptor mRNA was not increased after the onset of labour. Conclusions The human uterus is extremely sensitive to arginine vasopressin in vitro. Arginine vasopressin is produced by the fetus but fetal formation is not increased during labour. [source]

,1 Adrenoreceptors Mediate The Stimulatory Effects of Oestrogen On Stress-Related Hypothalamic-Pituitary-Adrenal Activity in The Female Rat

V. Viau
Abstract Variation in challenge-induced adrenocorticotropin hormone (ACTH) release over the oestrous cycle occurs in response to fluctuations in circulating concentrations of oestrogen and progesterone. However, how these ovarian steroids interact to regulate the principal ACTH cosecretagogues, corticotropin-releasing hormone (CRH) and arginine vasopressin is not understood. Here, we measured median eminence CRH and vasopressin content in intact cycling female rats, and in ovariectomized (OVX) females steroid-replaced in a manner that approximates the relative release patterns of oestrogen and progesterone seen over the oestrous cycle. Intact cycling females showed significantly higher median eminence CRH and vasopressin concentrations during proestrous and oestrous compared to the diestrous phase. In OVX rats, a single 10 g injection of oestrogen failed to mimic this increase in median eminence CRH and vasopressin. However, this dose significantly elevated CRH and vasopressin content in OVX rats previously exposed to diestrous concentrations of oestrogen and progesterone. Moreover, oestrogen priming enhanced restraint-induced depletion of CRH and vasopressin from the median eminence, but only against a background of low oestrogen and progesterone replacement. Oestrogen-induced elevations in median eminence vasopressin (but not CRH) content were reduced by peripheral administration of the ,1 adrenoreceptor antagonist prazosin. Finally, plasma ACTH concentrations following central injection of the ,1 receptor agonist, phenylephrine, were significantly higher in rats during proestrous compared to diestrous. These results indicate that the stimulatory effect of oestrogen on both the expression and stress-induced release of ACTH cosecretagogues is exerted only against a background of low oestrogen and progesterone levels, and is mediated, in part, via the ,1 adrenoreceptor. [source]