Organ culture specifically inhibits vasorelaxation to acute
hypoxia and preferentially decreases specific voltage-dependent K(+) channel expression over other K(+) and Ca(2+) channel subtypes. To isolate further potential
oxygen-sensing mechanisms correlated with altered gene expression, we performed differential display analysis on
RNA isolated from control and cultured coronary arterial rings. We hypothesize that organ culture results in altered gene expression important for vascular smooth muscle contractility important to the mechanism of
hypoxia-induced relaxation. Our results indicate a milieu of changes suggesting both up- and downregulation of several genes. The altered expression pattern of two positive clones was verified by Northern analysis. Subsequent screening of a porcine cDNA library indicated homology to the
ryanodine receptor (RyR). RT-PCR using specific primers to the three subtypes of RyR shows an upregulation of
RyR2 and
RyR3 after organ culture. Additionally, the
caffeine- and/or
ryanodine-sensitive intracellular Ca(2+) store was significantly more responsive to
caffeine activation after organ culture. Our data indicate that organ culture increases expression of specific RyR subtypes and inhibits hypoxic vasorelaxation. Importantly,
ryanodine blunted hypoxic relaxation in control coronary arteries, suggesting that upregulated RyR might play a novel role in altered intracellular Ca(2+) handling during
hypoxia.