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Integration of new regulatory strategies into the network of an endocrine control system: limitation of androgen secretion by rat testis is achieved by substrate‐dependent modulation of P450XVII enzyme concentration and catalytic efficiency *
Author(s) -
KühnVelten W. N.
Publication year - 2009
Publication title -
andrologia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.633
H-Index - 59
eISSN - 1439-0272
pISSN - 0303-4569
DOI - 10.1111/j.1439-0272.1992.tb02619.x
Subject(s) - androgen , steroid , secretion , endocrinology , testosterone (patch) , medicine , biology , pregnenolone , monooxygenase , hormone , steroid hormone , cytochrome p450 , steroid biosynthesis , microbiology and biotechnology , stimulation , chemistry , metabolism
Summary. In addition to the well‐known control circuits involved in the regulation and adaptation of testicular androgen biosynthesis, it is proposed that two new control strategies are involved in the maintenance of steady‐state testosterone secretion rates by testicular Leydig cells. Cytochrome P450XVII (steroid‐17α‐monooxygenase/steroid‐17,20‐lyase), one key enzyme in steroid hormone biosynthesis, responds to external human choriogonadotropin stimulation with an oxygen‐dependent and substrate flux‐dependent inactivation and decomposition, and increased substrate availability decreases the efficiency of androgen formation in favour of abortive intermediate leakage. These results are discussed as a paradigm of substrate‐dependent modulation of cytochrome P450 activities.