title: Role of diacylglycerol in adrenergic-stimulated 86Rb uptake by proximal tubules.
abstract: We used rat proximal tubule fragments purified by Percoll centrifugation to examine the role of diacylglycerol (DAG) in noradrenergic-stimulated Na+ reabsorption. Tubular DAG concentration and ouabain-inhibitable 86Rb uptake increased within 30 s after adding norepinephrine (NE) and remained elevated for at least 5 min. NE (1 microM) increased DAG content 17% and ouabain-inhibitable 86Rb uptake 23%. Cirazoline-stimulated 86Rb uptake was not inhibited by BaCl, quinidine, or bumetanide (1-10 microM) or by the omission of HCO3- or Cl- from the medium, but it was completely inhibited by ouabain and furosemide. Oleoyl-acetyl glycerol, L-alpha-1,2-dioctanoylglycerol, and L-alpha-1,2-dioleoylglycerol (DOG) increased total 86Rb uptake 8-11%. 12-O-tetradecanoylphorbol-13-acetate (TPA) (5 nM) increased uptake by only 4%. Staurosporine at 5 nM inhibited DOG stimulation completely, whereas 50 nM staurosporine was required to inhibit NE stimulation completely. Sphingosine inhibited DOG stimulation by 66% but did not inhibit NE stimulation. Amiloride (1 mM) completely blocked DOG stimulation. Monensin increased 86Rb uptake 31% and completely blocked the DOG effect but reduced the NE effect by only 26% (P = 0.08). In tubules from salt-loaded rats, NE did not increase DAG concentration, but NE-stimulated 86Rb uptake was reduced by only 23% (P = 0.15). Thus DAG released by NE may stimulate Na+ entry through Na(+)-H+ exchange. NE predominantly stimulates Na(+)-K(+)-adenosinetriphosphatase (ATPase) by activating a protein kinase that is insensitive to DAG and TPA and is inhibited by staurosporine but not by sphingosine. NE may also stimulate K+ efflux through a BaCl-insensitive K+ channel that is inhibited by millimolar furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Clinical Biochemistry, University of Toronto, Ontario, Canada.
authors.forename: A D
authors.initials: AD
authors.lastname: Baines
authors.forename: R
authors.initials: R
authors.lastname: Drangova
authors.forename: P
authors.initials: P
authors.lastname: Ho
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D004075:Diglycerides / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D005989:Glycerides / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008985:Monensin / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D009761:Nystatin / Q000494:pharmacology; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012413:Rubidium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012414:Rubidium Radioisotopes; D019311:Staurosporine; D013566:Sympathomimetics / Q000494:pharmacology*
chemical_list: D000470:Alkaloids; D004075:Diglycerides; D005989:Glycerides; D012414:Rubidium Radioisotopes; D013566:Sympathomimetics; D009761:Nystatin; D010042:Ouabain; D008985:Monensin; D011493:Protein Kinase C; D019311:Staurosporine; D012413:Rubidium; D009638:Norepinephrine