Metabolism of Progesterone by Rat Testicular Homogenates. II. Changes with Age

Abstract

Whole homogenates of testes from rats of different sizes have been incubated with progesterone-4-14 C and labeled products have been isolated and assayed for radioactivity. A marked change in the pattern of metabolites takes place when the rats are 200-300 g in weight (7-9 weeks). With testes from 150-200 g animals testosterone is formed in appreciable yields but to a great extent is further metabolized, principally to 5a-androstane-3a,17/?-diol. The ring A reductase activity responsible for this transformation appears to decrease during an early phase of rapid sexual maturation. It is suggested that this change in testicular enzymatic activities may play a role, and that 5«-androstane-3a,17/3-diol may serve some special function in the process of sexual maturation. {Endocrinology 78:1041,1966)

Leydig Cell Differentation, Steroid Metabolism by the Interstitium in Vitro and the Growth of the Accessory Sex Organs in the Rat

“…In the present work, the reduced yields of androsterone in vitro might have been due to a decline in substrate availability within the cells rather than to an intrinsic decline in the concentration of 5 areductase. While this seems inconsistent with the results of previous workers, interpretation in these cases was complicated by the use of preparations derived from whole testis (Nayfeh et al, 1966;Inano et al, 1967;Ficher & Steinberger, 1968). Studies complementary to the present work have failed to demonstrate the formation of androsterone in isolated seminiferous tubules (Tsang, Collins & Lacy, 1973 (Text-fig.…”

Age-Dependent Changes in Pituitarygonadal Relationships

“…1). Lisk (1968) (Nayfeh, Barefoot & Baggett, 1966) and an increased output of androgen in the spermatic vein (Hashimoto & Suzuki, 1966;Resko, Feder & Goy, 1968) (Text-fig. 2) while the growth of the seminal vesicles was much slower at this time (Text-fig.…”

Mechanisms of aging in relationship to steroid biotransformations and the thiobarbituric acid reactive material in rate testicular tissue in vitro

“…In this respect, Simpson and reported differences in the yield of 17a-hydroxyprogesterone and androgens with the time of incubation when a 3 kinetic study was undertaken for the conversion of pregnenolone-7a-H 14 and progesterone-4-C by minced adult murine testes. Noumura, Weiss, and Lloyd (1966) did not observe a significant decrease in the production of testosterone when the incubation time of rat fetal testes homogenates was increases from 30 minuses to 3 hours, but and Nayfeh, Barefoot, and Baggett (1966) did report a decrease in testosterone production and an increase in the formation of androstanediol when the time of incubation was similarly lengthened from 30 minutes to 3 hours. Nevertheless, it is difficult to speculate on how the changes in incubation time were reflected in the differences observed between minced and teased-tubular preparations, mainly because kinetic studies have not been performed to date with the teased-tubular preparations.…”

“…Testosterone/ androstenedione ratios were less than 1 for animals up to 60 days (not reported for older rats) regardless of the substrate utilized; however, a slight increasing trend from the youngest specimens to the older ones was evident. and Nayfeh, Barefoot, and Baggett (1966) incubated testicular homogenates from rats ranging between 155 and 564 grams of weight (age roughly corresponding from 5 weeks to 14 maturity). Progesterone-4-C was used as substrate.…”

“…27-day-old animals (Inano and Tamaoki, 1966), to that of 20-and 30-day-old animals (Inano, Hori, and Tamaoki, 1967) or to that of animals 4 to 5 weeks old (Nayfeh, Barefoot, and Baggett, 1966;Steinberger and.Ficher, 1968).…”