title: Parathyroid hormone stimulates ammoniagenesis in canine renal proximal tubular segments.
abstract: To determine whether parathyroid hormone (PTH) affects ammoniagenesis in renal proximal tubule, we measured ammonia production in suspensions of canine renal proximal tubular segments incubated with 10 mM L-glutamine in the absence or presence of 10(-7) M PTH. Productions of ammonia were linear functions of time for 120 min and averaged 231 +/- 55 and 311 +/- 67 mumol ammonia/g protein in the absence and presence of PTH, respectively. When measured over the range of 10(-11)-10(-7) M PTH, half-maximal stimulation of ammonia production occurred between 10(-10) and 10(-9) M PTH. Maximal production of ammonia was observed at 10(-8) M PTH. Incubation of proximal tubular segments with PTH increased levels of adenosine 3',5'-cyclic monophosphate (cAMP) in vitro. Ammonia production was significantly enhanced by incubation of segments with the cAMP analogue, 8-bromoadenosine 3',5'-cyclic monophosphate. PTH also increased ammonia production in segments incubated with 1 mM L-glutamine. We conclude that PTH stimulates ammonia production in canine renal proximal tubular segments. This effect appears to be mediated, at least in part, through cAMP in vitro. Such stimulation could reflect a direct action of PTH on the proximal tubule to enhance ammoniagenesis in vivo.
authors.affiliation: Department of pediatrics, University of Wisconsin, Madison 53792.
authors.forename: M C
authors.initials: MC
authors.lastname: Chobanian
authors.forename: M R
authors.initials: MR
authors.lastname: Hammerman
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D005973:Glutamine; C025076:parathyroid hormone (1-34), bovine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000641:Ammonia; D000242:Cyclic AMP; D005947:Glucose