Hemoproteins hepatic microsomal

Sladek, N.E. and Mannering, C.J. Evidence for a new P-1+50 hemoprotein in hepatic microsomes from methylcholanthrene treated rats. Biochem. Biophys. Res. Commun. (1966) 2l+, 668-671+. 

In an attempt to resolve these questions, we have directed studies toward examining the interaction of chemicals with the hepatic microsomal monooxygenase system of fish and to determine whether multiple forms of hemoprotein(s) P-450 exist, and, if so, how the relative microsomal hemoprotein subpopulations are altered by xen ob i oti cs. 

Table II demonstrates the effect of two polychlorinated biphenyl mixtures (Aroclors 1254 and 1242), a polybrominated biphenyl mixture (Firemaster BP6), phenobarbital and -naphtho-flavone on various hemoprotein P-450-mediated monooxygenase activities of rainbow trout hepatic microsomes.

The alteration of hemoprotein(s) P-450 subpopulations in the rat may be observed spectrally, because after treatment of rats with polycyclic aromatic hydrocarbons, the Soret maximum of the carbonmonoxyferrocytochrome complex undergoes a hypsochromic shift from 450 to 448nm (50). This blue shift was not seen with rainbow trout hepatic microsomes (29,30). However, this does not preclude the induction of novel hemoproteins P-450 since (a) the induced hemoprotein(s) maty not differ spectrally from the constitutive enzymes and (b) the induced-hemoprotein may account for only a small proportion of total hemoprotein P-450, and hence its contribution to the position of the Soret maximum of carbon monoxide-treated reduced microsomes may be negligible. The latter suggestion is supported by the work of Bend et al. with the little skate. These workers have shown that hepatic microsomes from 1, 2,3,4-dibenzanthracene treated skates did not exhibit a hypsochromic shift when compared to control microsomes, however, partially purified hemoprotein exhibited an absorbance maxima at 448 nm (51). 

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