title: Breeding condition, temperature, and the regulation of salt and water by pituitary hormones in the red-spotted newt, Notophthalmus viridescens.
abstract: In vivo integumental transepithelial potential (TEP) in the Eastern red-spotted newt (Notophthalmus viridescens) increases linearly with external [Na+] from 0.1 to 10 mM and is anion independent. Both integumental TEP and osmotic permeability are higher in laboratory-conditioned (LC, terrestrial) than in breeding-condition (BC, aquatic) newts at temperatures of 5-25 degrees. Prolactin (PRL) treatment of LC newts decreased both TEP and rate of water uptake. Arginine vasotocin (AVT) treatment resulted in a substantial increase in water uptake in LC newts, while little or no AVT response was seen in PRL-treated or BC newts. Hypophysectomy (HX) or ergocryptine treatment increased TEP in BC newts, whereas HX + PRL maintained TEP at control levels. Although ergocryptine and HX were without effect on water uptake in BC newts kept at 5 degrees for 9 days, HX + ACTH increased water uptake. HX produced a substantial fall in serum [Na+] in BC newts, while either PRL or ACTH replacement elevated serum [Na+]. Combined ACTH and PRL treatment returned serum [Na+] to control levels. These data suggest that high endogenous prolactin plays a significant role in maintaining serum [Na+] and integumental permeability and transport characteristics in breeding-condition N. viridescens. Although PRL and ACTH are both sodium retaining in the aquatic breeding stage, these two hormones promote opposite effects on the integument; PRL decreases both water uptake and integumental TEP, whereas ACTH (presumably acting through the adrenals) increases water uptake and possibly TEP.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage; D000818:Animals; D001947:Breeding; D007016:Hypophysectomy; D009673:Notophthalmus viridescens / Q000502:physiology*; D009995:Osmosis; D010539:Permeability; D011388:Prolactin / Q000502:physiology*; D012455:Salamandridae / Q000502:physiology*; D012867:Skin / Q000378:metabolism; D012879:Skin Physiological Phenomena; D012964:Sodium / Q000097:blood; D012965:Sodium Chloride / Q000378:metabolism; D013696:Temperature; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D012965:Sodium Chloride; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D012964:Sodium