Role of protein kinase C in parathyroid hormone stimulation of renal 1,25-dihydroxyvitamin D3 secretion.
PTH is a major regulator of renal proximal tubule 1,25(OH)2D3 biosynthesis. However, the intracellular pathways involved in PTH activation of the mitochondrial 25-hydroxyvitamin D3-1 alpha-hydroxylase (1-OHase) remain unknown. PTH can activate both the adenylate cyclase/protein kinase A (PKA) and the plasma membrane phospholipase C/protein kinase C (PKC) pathways. The present study was undertaken to determine whether PKC may mediate PTH activation of renal 25-hydroxyvitamin D3-1 alpha-hydroxylase activity. Rat PTH 1-34 fragment in vitro translocated PKC activity from cytosolic to soluble membrane fraction from freshly prepared rat proximal tubules. Physiologic concentrations (10(-11)-10(-10) M) of rat PTH 1-34 fragment increased PKC translocation three- to fourfold while PKA activity ratio increased at PTH 10(-7) M. PTH stimulation of PKC and PKA was reduced in the presence of staurosporine (10 nM) by 41 and 29%, respectively. Sangivamycin (10 and 50 microM) also reduced PTH-stimulated PKC translocation, but did not alter PKA activity ratio. In vitro perifusion of renal proximal tubules with PTH (10(-11) M) increased 1,25(OH)2D3 steady-state secretion two- to fourfold. Sangivamycin at the same concentration that inhibited PKC translocation by 52% completely inhibited PTH-stimulated 1,25(OH)2D3 secretion. The present studies indicate that the phospholipase C/PKC pathway may mediate PTH stimulation of mammalian renal proximal tubule 1,25(OH)2D3 secretion.
Janulis
M
M
Department of Medicine, University of Chicago Pritzker School of Medicine, Illinois 60637.
Tembe
V
V
Favus
M J
MJ
D000818:Animals; D002117:Calcitriol / Q000378:metabolism*; D002451:Cell Compartmentation / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D010281:Parathyroid Hormone; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D002117:Calcitriol