Development of radioimmunoassays for ovine neurophysins. Correlation of neurophysin release with oxytocin- and vasopressin-related stimuli.
Specific homologous RIAs for the ovine neurophysins (oN-I/II, oN-III) were established; the assays had a sensitivity capable of measuring basal levels of the pituitary proteins in sheep plasma. Reduction in blood volume of ewes caused a 200-fold increase in oN-III with minimal changes in oN-I/II levels. After infusion of either hypertonic saline or nicotine, a similar specific increase in oN-III was observed, occurring at a time when the free water clearance rate decreased. Intramuscular administration of estradiol benzoate caused an increase in jugular plasma oN-I/II concentrations without affecting the oN-III concentrations. In one of six lactating ewes, there was an increase in oN-I/II during suckling. The release of oN-I/II, which was accompanied by small increases in oN-III, exhibited a pulsatile profile similar to that reported for the secretion of oxytocin under similar conditions. During vaginal distension, increases in intramammary pressure were accompanied by elevations in levels of oN-I/II and oN-III. It is concluded that oxytocin-related events are associated predominantly with the release of oN-I/II and that stimuli that induce vasopressin release also cause elevation of oN-III. These correlations are consistent with our previous conclusion from biochemical and amino acid sequence analysis of the oNs.
D000595:Amino Acid Sequence; D000818:Animals; D003429:Cross Reactions; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007774:Lactation; D009481:Neurophysins / Q000097:blood*; D009538:Nicotine / Q000494:pharmacology; D011247:Pregnancy; D011863:Radioimmunoassay / Q000379:methods; D012756:Sheep
D009481:Neurophysins; D004958:Estradiol; D009538:Nicotine