Endocrinological Control and Cellular Localization of Rat Testicular Angiotensin-Converting Enzyme (EC 3.4.15.1)

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Abstract
Hypophysectomy of prepubescent (3-wk-old) rats prevented the pubertal development of testicular, but not pulmonary, angiotensin-converting enzyme (EC 3.4.15.1). Additionally, hypophysectomy resulted in a loss of testicular converting enzyme activity in 10 wk old rats that had achieved puberty and had developed enzyme activity. Hormone regimens consisting of FSH/LH [luteinizing hormone] (7.5 U/rat .cntdot. day), hCG [human chorionic gonadotropin] (10 U/rat .cntdot. day), or testosterone(1 mg/rat .cntdot. day) were employed to ascertain their ability to maintain activity in hypophysectomized rats. All three of the above hormone regimens, if initiated on the 1st day after hypophysectomy of 10 wk-old rats, were capable of maintaining testicular converting enzyme activity. Centrifugal elutriation of dispersed testicular cells indicated that the majority of enzyme activity in mature rats was associated with the germinal cells, a result consistent with the data accumulated from the hormonal studies. Lastly, [3H]captopril bound specifically to cellular fractions enriched in germinal cells. Apparently, the pituitary gland is required for the development and maintenance of testicular angiotensin-converting enzyme in the rat by stimulating steroidogenesis in the testes. Furthermore, the sensitivity of converting enzyme activity to androgen, coupled with the centrifugal elutriation and [3H]captopril binding studies, strongly support the notion that testicular converting enzyme is associated with germinal cells.