Beta-receptor-adenylate cyclase coupling in hypoxic neonatal rat ventricular myocytes.
This study investigated the influence of hypoxia on alterations in the beta-adrenergic receptor-adenylate cyclase system. Cultured neonatal rat ventricular myocytes were subjected to normoxia (incubator PO2 135-145 mmHg) or hypoxia (incubator PO2 0-14 mmHg) and, in crude membrane preparations, beta-receptor binding properties were measured with [125I]iodocyanopindolol and adenylate cyclase activity by radioimmunoassay. Hypoxia of 30 min in duration caused no alteration in beta-receptor density (Bmax 75 +/- 11 vs. 71 +/- 12 fmol/mg protein) but increased adenylate cyclase activity under basal conditions and during stimulation with l-isoproterenol, 5'-guanylimidotriphosphate [Gpp(NH)p] 5 X 10(-5) M, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + guanosine 5'-triphosphate (GTP) 5 X 10(-5) M gave 221 +/- 34 vs. 143 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. After 60 min of hypoxia, adenylate cyclase activity was no longer increased. Hypoxia of 120-150 min duration increased Bmax by 64% (73 +/- 8 to 120 +/- 11 fmol/mg protein, P less than 0.05 vs. normoxia) but decreased adenylate cyclase activity during stimulation with isoproterenol, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + GTP 5 X 10(-5) M gave 107 +/- 12 vs. 148 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. Reoxygenation for 15 min following 120-150 min of hypoxia reversed the increased beta-receptor numbers and decreased adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Thandroyen
F T
FT
Department of Internal Medicine (Cardiology), University of Texas, Southwestern Medical Center, Dallas 75235.
Muntz
K
K
Rosenbaum
T
T
Ziman
B
B
Willerson
J T
JT
Buja
L M
LM
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003327:Coronary Disease / Q000378:metabolism; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000502:physiology*; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013997:Time Factors
D011943:Receptors, Adrenergic, beta; D000262:Adenylyl Cyclases; D010100:Oxygen