title: Changes in cytochrome P-450 iron spin state as a function of castration, testosterone or estrogen treatment, vigorous exercise, or starvation.
abstract: 3-Methylcholanthrene treatment induced large increases in high-spin P-450 form(s) in intact microsomal membranes from New Zealand White rabbit or C57BL/6N mouse liver but not in rabbit lung, kidney or intestine. Testosterone enhanced the high-spin/low-spin ratio of P-450 in female C57BL/6N liver to the same degree as 3-methylcholanthrene treatment; there was no additive increase in the ratio with treatment of testosterone plus 3-methylcholanthrene. The same effect was seen in ovariectomized females. In the liver of normal or castrated C57BL/6N mice, estradiol-17 beta pretreatment caused no significant change in the high-spin/low-spin ratio. Vigorous homogenization of the microsomes can decrease the high-spin/low-spin ratio, more so in control than in 3-methylcholanthrene-induced C57BL/6N microsomes. Vigorous exercise (20-min swim) and fasting for 2 days significantly enhanced the high-spin/low-spin ratio in C57BL/6N liver. Temperature studies showed that the low-spin electron paramagnetic resonance signal intensity, as a function of absolute temperature in the range of 16 to 70 degrees K, was consistent with a simple Boltzmann dependence within the Kramers doublet giving rise to the microwave transition. We conclude that, within the limits of measurement, the low-spin state acts like an isolated state and is not in thermal equilibrium with the high-spin form of P-450.
mesh_terms: D000818:Animals; D002369:Castration; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D004967:Estrogens / Q000494:pharmacology*; D007501:Iron / Q000032:analysis*; D008748:Methylcholanthrene / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008861:Microsomes / Q000201:enzymology; D005082:Physical Exertion; D011817:Rabbits; D013217:Starvation / Q000201:enzymology*; D013696:Temperature; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D004967:Estrogens; D013739:Testosterone; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D007501:Iron