Genetic Control of Serum Marinobufagenin in the Spontaneously Hypertensive Rat and the Relationship to Blood Pressure

Abstract

BackgroundWe have investigated serum levels of immunoreactive marinobufagenin (MBG) in 16‐ to 20‐week‐old spontaneously hypertensive rats (SHRs)‐A3 and in the normotensive Wistar‐Kyoto (WKY) rat strain in the absence of salt loading, and we have investigated the genetic control of serum MBG.Methods and ResultsWe genotyped the F2 progeny of an SHR‐A3×WKY intercross using a genome‐wide panel of 253 single‐nucleotide polymorphism markers that were dimorphic between SHR‐A3 and WKY and measured serum MBG by ELISA. Serum MBG levels were lower in SHR‐A3 than WKY rats (0.39±0.07 and 1.27±0.40 nmol/L, respectively), suggesting that MBG may not play a role in the markedly divergent blood pressure measured by telemetry in rats of these 2 strains (SHR‐A3 and WKY, 198.3±4.43 and 116.8±1.51 mm Hg, respectively). The strain difference in serum MBG was investigated to determine whether genomic regions influencing MBG might be identified by genetic mapping. Quantitative trait locus mapping indicated a single locus influencing serum MBG in the region of chromosome 6q12. Homozygosity of WKY alleles at this locus was associated with increased serum MBG levels. We surveyed whole genome sequences from our SHR‐A3 and WKY lines, seeking coding sequence variation between SHR‐A3 and WKY within the mapped locus that might explain the inherited strain difference in serum MBG.ConclusionsWe identified amino acid substitution in the sterol transport protein Abcg5, present in SHR‐A3, but absent in WKY, that is a potential mechanism influencing MBG levels.

Sensational site: the sodium pump ouabain-binding site and its ligands

“…After 9–12 wk on the HS diet, however, when the rats went into HF, MBG fell to the control level while eOLC rose to about triple the control level ( 473 ). Finally, in spontaneously hypertensive rats (SHR), MBG was lower than it was in the control Wistar-Kyoto (WKY) rats, but eOLC was not measured ( 474 ). Thus, the link between MBG and hypertension appears more tenuous than the link to EO.…”