Convertibility of a saponifiable lipoidal derivative of 18-hydroxycorticosterone.
Metabolic properties and subcellular localization of the biosynthesis of SM, a saponifiable 18-OH-B (18-Hydroxycorticosterone) derivative, were investigated. Homogenates biosynthesized SM at a nearly constant rate of 463 pmol/50 mg tissue during 30 min. This biosynthesis was more efficient at pH 7.4 than at pH 4.8. Not only 18-OH-B but also its less polar anhydride 18-DAL (18-Deoxyaldosterone) were good precursors. SM was reverted to these precursors both enzymatically and spontaneously, 4.8 being a more suitable pH for this reversion than 7.4. Trapping experiments demonstrated a sequence comprising, in this order, the following echelons: SM, 18-OH-B, 18-DAL, Aldosterone. The first two steps are reversible and the last two ones depend on proton concentrations. It is postulated that SM could be on a dead-end to which 18-OH-B could be deviated if Aldosterone biosynthesis became temporarily unnecessary. Also, that 18-OH-B may convert to either 18-DAL or SM for selective membrane transports, according to homeostatic requirements.
Cozza
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EN
PRHOM (CONICET), Buenos Aires, Argentina.
Ceballos
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NR
Vila
M C
MC
Lantos
C P
CP
D015069:18-Hydroxycorticosterone / Q000378:metabolism*; D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003345:Corticosterone / Q000031:analogs & derivatives*; D003600:Cytosol / Q000378:metabolism; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility; D013347:Subcellular Fractions / Q000378:metabolism
D015069:18-Hydroxycorticosterone; D003345:Corticosterone