Bovine 'neurophysin II' stimulates growth hormone release in the estradiol-primed male rat.
Basal plasma concentrations of growth hormone (GH) were monitored in both normal and estradiol-primed male rats by the collection of sequential blood samples from freely moving rats, via chronic intraatrial cannulae. Blood was sampled every 2 min for a period of 80 min and plasma GH levels determined by radioimmunoassay. The normal male rats displayed a pulsatile release of GH, while the estradiol-primed male rats exhibited a relatively steady level of plasma GH concentration. The rats exposed to high levels of estradiol (1.59 +/- 0.42 nmol/l plasma) also had a higher mean value of basal GH concentration. An injection of 100 micrograms/kg of bovine neurophysin II did not alter GH release in the normal male rats. However, it did significantly elevate GH levels in the estradiol-primed animals to a mean peak level approximately six times the mean basal level. The administration of 100 micrograms/kg of bovine neurophysin I to estradiol-primed male rats did not produce any change in plasma GH levels and thus eliminates the possibility of the nonspecific stimulation of neurophysin II on GH release.
Papas
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Department of Physiology, Queen's University, Kingston, Ont., Canada.
Shin
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Obonsawin
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MC
D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage*; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D009481:Neurophysins / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D004343:Drug Implants; D009481:Neurophysins; D004958:Estradiol; D013006:Growth Hormone