title: Changes in plasma arginine vasopressin concentration during lactation in rats.
abstract: OBJECTIVE
  The objectives of the study reported here were to determine whether a change in the plasma arginine vasopressin (AVP) concentration occurred in lactating, compared with non-lactating rats and to examine the involvement of suckling with plasma AVP concentration.
  
  
  METHODS
  Experiments were performed on 86 female Wister Imamichi rats, 12 weeks old at parturition, with fast lactation. On day 13 of lactation, AVP concentration and plasma osmotic pressure were measured in lactating and non-lactating rats.
  
  
  RESULTS
  Plasma AVP concentration was always higher in rats of the lactating groups than in non-lactating controls (1.06 +/- 0.28 pg/ml), and a conspicuous increase in AVP concentration was seen during the postsuckling period (1.70-0.61 pg/ml before vs. 2.56 +/- 1.31 pg/ml after suckling, P < 0.05). Plasma osmotic pressure in lactating rats with 12 pups (296.6 +/- 5.2 mOsmol/kg x H2O) was lower than that in rats of the removed control groups (306.7 +/- 5.7 mOsmol/kg x H2O).
  
  
  CONCLUSIONS
  On the basis of these results, it appears that "low plasma osmotic pressure-high AVP status" develops in the lactating period, similar to pregnancy, through resetting of the regulatory mechanism of the AVP system. It was concluded that suckling stimulation could release AVP, which could dilute the blood with water resulting in the increase in circulating blood volume.
authors.affiliation: Department of Veterinary Internal Medicine, Nippon Veterinary and Animal Science University, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: N
authors.initials: N
authors.lastname: Koizumi
authors.forename: H
authors.initials: H
authors.lastname: Hirose
authors.forename: R
authors.initials: R
authors.lastname: Hokao
authors.forename: N
authors.initials: N
authors.lastname: Takemura
authors.forename: S
authors.initials: S
authors.lastname: Motoyoshi
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood*; D001769:Blood; D005260:Female; D006400:Hematocrit; D007774:Lactation / Q000097:blood*; D009997:Osmotic Pressure; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000097:blood
chemical_list: D001127:Arginine Vasopressin; D012964:Sodium