Decreased intracellular calcium stimulates renin release via calcium-inhibitable adenylyl cyclase.
Intracellular calcium and cAMP are the 2 second messengers that regulate renin release; cAMP stimulates renin release from juxtaglomerular (JG) cells, whereas increased intracellular calcium inhibits it. We hypothesized that decreased intracellular calcium acts by activating calcium-inhibitable isoforms of adenylyl cyclase, increasing cAMP, and stimulating renin secretion. We used a primary culture of JG cells isolated from C-57/B6 mice. Cells were plated to a density of 70% in serum-free medium and incubated for 2 hours with or without 100 micromol/L of the cytosolic calcium chelator 5'5-dimethyl-1,2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid (BAPTA-AM) to decrease intracellular calcium. JG cell cAMP content and renin release were determined by radioimmunoassay. Intracellular cAMP content was 4.04+/-0.92 pM/mL per milligram of protein, and it increased by125+/-33% (P<0.01) with BAPTA-AM. Basal renin was 1.28+/-0.40 microg of angiotensin I per milliliter per hour per milligram of protein, and BAPTA-AM increased it by 182+/-62% (P<0.025). Western blots using an antibody that recognizes adenylyl cyclase types V and VI yielded a characteristic band of approximately 135 kDa. When primary cultures of isolated JG cells were tested for the calcium-inhibitable isoforms of adenylyl cyclase, they showed intense focal cytoplasmic staining. Cells stained for both renin and adenylyl cyclase V/VI showed colocalization in the cytoplasm, primarily on the granules. An adenylyl cyclase inhibitor (SQ 22,536) completely blocked BAPTA-AM-stimulated renin release and JG cell cAMP content. We conclude that calcium-inhibitable isoform(s) of adenylyl cyclase (types V and/or VI) exist within the JG cell. Thus, decreased intracellular calcium stimulates adenylyl cyclase, resulting in cAMP synthesis and, consequently, renin release.
Ortiz-Capisano
M Cecilia
MC
Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit,MI 48202, USA.
Ortiz
Pablo A
PA
Harding
Pamela
P
Garvin
Jeffrey L
JL
Beierwaltes
William H
WH
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007606:Juxtaglomerular Apparatus / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D012083:Renin / Q000378:metabolism*; D014018:Tissue Distribution
D000067956:Adenylyl Cyclase Inhibitors; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D007527:Isoenzymes; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; C017759:9-(tetrahydro-2-furyl)-adenine; D004533:Egtazic Acid; D000242:Cyclic AMP; D012083:Renin; D000262:Adenylyl Cyclases; D000225:Adenine; D002118:Calcium