Ri. Dmitrieva et al., Mammalian bufadienolide is synthesized from cholesterol in the adrenal cortex by a pathway that is independent of cholesterol side-chain cleavage, HYPERTENSIO, 36(3), 2000, pp. 442-448
Citations number
50
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
An increasing body of evidence suggests that an endogenous mammalian bufadi
enolide (BD) may be involved in the regulation of Na+,K+-ATPase activity an
d the pathogenesis of arterial hypertension. We developed a purification sc
heme for marinobufagenin (MBG), an amphibian cardiotonic ED, and applied it
to purify and characterize material in human plasma, culture medium condit
ioned by Y-1 adrenocortical cells, and rat adrenal tissue. MBG immunoreacti
vity purified from plasma and measured by ELISA showed important similariti
es (chromatography and antibody cross-reactivity) to material secreted into
cell culture medium by Y-1 cells. This observation indicates that circulat
ing mammalian ED may have an adrenocortical origin. Release of mammalian ED
from adrenocortical cells grown in the absence of exogenous cholesterol wa
s reduced by treatment of cultures with mevastatin, a 3-hydroxy-3-methylglu
taryl coenzyme A reductase inhibitor. Supplementation of the serum and chol
esterol-free cell culture medium with the LDL fraction of human plasma incr
eased the production of MBG material in the presence of mevastatin, support
ing its origin from cholesterol. We used Y-1 cell lines transfected with ge
nes shown to inhibit steroidogenesis through cholesterol side-chain cleavag
e (Y-1/DAX and Y-1/RIAB) to investigate the dependence of MBG biosynthesis
on side-chain cleavage. Our results indicate that the mammalian ED is synth
esized in the adrenal cortex from cholesterol and shares important similari
ties with the amphibian ED MEG, that its biosynthesis is independent of tra
nsfer of cholesterol to the side-chain cleavage enzyme complex mediated by
steroidogenic acute regulatory protein, and that neither cAMP nor protein k
inase A appears to be a critical component of the pathway controlling its b
iosynthesis.