Effect of ovariectomy and treatment with ovarian steroids on vasopressin release and fluid balance in the rat.
Plasma vasopressin concentrations have previously been shown to vary during the oestrous cycle of the rat, being highest on the morning of pro-oestrus and lowest on dioestrus day 1. To determine the effect of gonadal steroids on vasopressin secretion and fluid balance, mature rats were ovariectomized and given oestrogen, progesterone or vehicle alone s.c. for periods of up to 16 days. Plasma vasopressin concentrations fell after ovariectomy and this was reflected in an increase in 24-h urine volume. The normal increase in plasma vasopressin concentrations seen over day-light hours was also suppressed. The change in vasopressin concentrations observed on steroid treatment depended upon both the dose and the duration. High doses of oestrogen were associated with a fall in plasma vasopressin, probably as a result of fluid retention. Thus, of an initial group of rats given silicone elastomer implants containing 50, 500 or 1000 micrograms oestradiol in oil, plasma vasopressin concentrations were reduced after 7 days treatment with 1000 micrograms oestradiol implants in association with reduced plasma sodium concentrations. Daily s.c. injections of 100 micrograms oestradiol benzoate/100 g body weight produced an immediate small increase in plasma vasopressin concentrations, but by 14 days the plasma concentrations of 0.7 +/- 0.16 pmol/l (mean +/- S.E.M.) had fallen significantly and were less than those in the vehicle-treated group (1.2 +/- 0.26 pmol/l). However, after treatment for 14 days with implants containing only 50 micrograms oestradiol, plasma vasopressin concentrations were higher compared with the group receiving vehicle alone, despite the fact that the plasma osmolality was lower in the latter group, suggesting a long term resetting of the osmoreceptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Peysner
K
K
Department of Physiology, University College and Middlesex School of Medicine, University College London.
Forsling
M L
ML
D000818:Animals; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007279:Injections, Subcutaneous; D009994:Osmolar Concentration; D010052:Ovariectomy; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014554:Urination; D014667:Vasopressins / Q000097:blood*; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D004343:Drug Implants; D014667:Vasopressins; D011374:Progesterone; D004958:Estradiol