Effects of prolactin, adrenocorticotrophin, neurohypophysial peptides, cortisol, and androgens on some osmoregulatory parameters of the hypophysectomized catfish, Heteropneustes fossilis (bloch).
Daily injections of ovine prolactin (PRL), cortisol acetate (FA), arginine vasotocin (AVT), and adrenocorticotrophic hormone (ACTH), at doses ranging from 0.1 to 500 mU/g, 0.2 to 25 micrograms/g, 0.01 to 0.02 micrograms/g, and 5 to 10 mU/g respectively, for 5 days elevated plasma osmolarity and plasma sodium levels in the 3-day hypophysectomized catfish, Heteropneustes fossilis maintained in tap water. PRL enhanced urine production and decreased urine osmolarity and sodium concentration. Administration of FA and AVT increased urine output as well as urine osmolarity and sodium concentration, thereby resulting in severe natriuresis. Simultaneous administration of PRL and FA to hypophysectomized catfish restored plasma osmolarity and sodium concentration to normal levels even in the presence of increased urinary salt loss. However, if the fishes were maintained in deionized water, administration of PRL and FA had no effect on plasma osmolarity or plasma sodium levels suggesting that these hormones increase plasma osmotic pressure by stimulating active uptake of salts from the external medium. Neither PRL nor AVT evoked any increase in plasma cortisol level indicating that their effects on catfish osmoregulation are not mediated through cortisol production. Isotocin, testosterone, and delta 4-androstenedione had no effect on any of the plasmatic or urinary parameters. It is concluded that prolactin, cortisol, and AVT are the principal hormones for osmoionic homeostasis in this catfish and that they act through independent mechanisms.
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D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D005399:Fishes / Q000502:physiology; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006854:Hydrocortisone / Q000494:pharmacology*; D007016:Hypophysectomy; D008297:Male; D009318:Natriuresis / Q000187:drug effects; D010121:Oxytocin / Q000031:analogs & derivatives / Q000494:pharmacology; D010909:Pituitary Hormones, Posterior / Q000494:pharmacology*; D011388:Prolactin / Q000494:pharmacology*; D012756:Sheep; D014668:Vasotocin / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D000728:Androgens; D010909:Pituitary Hormones, Posterior; D010121:Oxytocin; C008215:isotocin; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D014668:Vasotocin; D006854:Hydrocortisone