Relationship between zonal distribution of microsomal cytochrome P-450s (P-450(17)alpha,lyase and P-450C21) and steroidogenic activities in guinea-pig adrenal cortex.
In an attempt to elucidate the functional role of the three zones of the adrenal cortex, the localization of microsomal cytochrome P-450s (P450(17)alpha,lyase and P-450C21) and their relation to steroidogenesis in the guinea-pig adrenal cortex were studied. The intracellular localization and zonal distribution of P-450(17)alpha,lyase and P-450C21 were examined by the direct peroxidase-labelled antibody technique. The cytochromes were localized immunocytochemically on the smooth-surfaced endoplasmic reticulum. P-450(17)alpha,lyase was found to be distributed in the zona fasciculata, especially in the externa, and less in the zona reticularis. The zona glomerulosa was negative for immunohistochemical staining for P-450(17)alpha,lyase. In contrast, P-450C21 was distributed in all three zones in the adrenal cortex. The cytochrome P-450 contents and their steroidogenic activities were determined with microsomes prepared from the outer zone (zonae glomerulosa and fasciculata) and from the inner zone (zona reticularis) of guinea-pig adrenals. Using an enzyme-linked immunosorbent assay, the ratio of P-450C21 content in the inner zone to that in the outer zone microsomes was estimated to be 1.24. 21-Hydroxylase activity was higher in the inner zone microsomes, which was in good agreement with the relative P-450C21 contents. The ratio of P-450(17)alpha,lyase content in the inner zone to that in the outer zone microsomes was estimated to be 0.75. 17 alpha-Hydroxylase and C17-20-lyase activities were five- to sixfold greater in the outer than in the inner zone microsomes, which could not be explained by the P-450(17)alpha,lyase contents in the two zones.(ABSTRACT TRUNCATED AT 250 WORDS)
Shinzawa
K
K
Department of Physiological Chemistry, Hiroshima University of Medicine, Japan.
Ishibashi
S
S
Murakoshi
M
M
Watanabe
K
K
Kominami
S
S
Kawahara
A
A
Takemori
S
S
D000311:Adrenal Glands / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006168:Guinea Pigs; D007016:Hypophysectomy; D007124:Immunoenzyme Techniques; D008297:Male; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology*; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism*; D013255:Steroid 21-Hydroxylase / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*
D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase; D013254:Steroid 17-alpha-Hydroxylase