[Steroid hormone transformation in the gonads and liver of aged rats]. / Steroidhormon-Transformation in Gonaden und Leber von Ratten im hohen Alter.

In order to study some aspects of the steroid hormone balance in old age the following organ functions of young and senescent male and female animals were investigated: 1) The capacity of testicular (45, 68-75 and 900 day-old animals) and ovarian tissue homogenates (29, 45, 66 and 900 day-old animals) to metabolically transform the sex hormone precursor, progesterone. 2) The capacity of liver slices (60-90 and 900 day-old animals) to generate a sex-specific metabolite pattern during incubation with testosterone. 3) The activities of some enzymes of steroid metabolism, which normally show sex differences in liver cell fractions (60-90 and 900 day-old animals). The testicular capacity of senescent animals to synthesize 17 alpha-hydroxyprogesterone, androstenedione and testosterone (main pathway of androgen biosynthesis) is drastically reduced compared to that of young adult rats; the reduction also extends to the production of highly polar C19O3- and C21O3-steroids. In contrast to these deficiencies, conversion of progesterone to 20 alpha-dihydroprogesterone increases in old age, whereas the generation of 5 alpha-hydrogenated compounds from testosterone and androstenedione remains unchanged. If the group of adolescent 45 day-old animals is also taken into consideration, then the biosynthetic sequence from progesterone to testosterone exhibits a biphasic developmental course. Production rates rise from low levels only to fall back to lower rates of synthesis in old age. In no age group can the production of oestrogens in measurable quantities be detected. However, 5 alpha-hydrogenated C19O2-steroid metabolites are detected, albeit only in prepuberal animals. After puberty only progesterone, 20 alpha-dihydroprogesterone and the 5 alpha-pregnane derivatives of these two steroids can be demonstrated. The pattern of the respective metabolites undergoes an age-dependent metabolite-specific development ending (900 day-old animals) with minimal yields of products (less than 21% of progesterone is converted). The production of hydroxylated metabolites (highly polar C21O3-steroid fraction) decreases very early in life (between day 29 and 45) to values indistinguishable from those of old animals. The sexually highly differentiated metabolite pattern of hepatic testosterone metabolism typical of young adult animals (60-90 day-old) is not prominent in old age. Both sexes exhibit a retarded testosterone turnover due to a decrease in the hydroxylating activity (males being more affected than females) and a deficiency of 5 alpha-hydrogenation (females only).(ABSTRACT TRUNCATED AT 400 WORDS)

Contradictory evidence concerning the "universal" role of growth hormone in the regulation of the enzyme activities of hepatic steroid metabolism.

Recent publications suggest that the sexual dimorphism observed in the activities of enzymes involved in drug and steroid metabolism in rat liver are due to sex-specific differences in the rate of growth hormone release. In this paper we set out to demonstrate that this hypothesis cannot be generalized, but has its limitations. Prepuberal hypophysectomy led to the expected "masculinization" of the activities of cytoplasmic 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSDH), microsomal 3 alpha-HSDH and microsomal 5 alpha-reductase which could be reversed by continuous infusion of human growth hormone (hGH). However, one activity did not conform to this pattern: cytoplasmic 17 beta-HSDH activity reacted to hypophysectomy with a "feminization" and was completely unaffected by hGH infusion. Moreover, microsomal 3 alpha-HSDH in hypophysectomized rats was "feminized" as efficiently by infusion of ovine prolactin (oPRL) as by hGH. Ablation of the pituitary caused loss of measurable cytoplasmic receptor oestrogen concentrations. The inability of either hypophyseal hormone to cause consistent and significant elevation of oestrogen receptor concentrations is probably due to the early age at which the animals were hypophysectomized.

Effects of exogenous dehydroepiandrosterone sulphate on various enzymes and on steroid metabolism in the guinea-pig.

Treatment of male guinea-pigs daily with an oral dose of 2 mg dehydroepiandrosterone (DHA) sulphate/100 g body weight for 2 weeks significantly reduced the glucose-6-phosphate dehydrogenase (G-6-PDH) activity of erythrocytes, liver, kidney and testis. Lactate dehydrogenase activity in plasma also decreased, but L-aspartate: 2-oxoglutarate aminotransferase (GOT) and L-alanine:2-oxoglutarate aminotransferase (GPT) activity in plasma remained unaffected. In liver and kidney, however, a significant rise in GOT and GPT was observed. A 2- to 3-7-fold increase of C19-steroids was observed in plasma, liver and kidney. In extracts of liver and kidney more than 60% of steroids were isolated from the sulphatide fraction. Only minor changes were detected in the metabolic pattern of C19-steroids, 17-hydroxysteroids prevailing in the free and sulphatide fractions, while 17-oxosteroids predominated in the sulphate and glucuronide fractions. A slight rise of cyclic AMP concentrations in liver and kidney tissue was attributed to the inhibition of phosphodiesterase by the DHA/G-6-PDH system