S. Milković

The development of sex differences in the adrenal morphology and responsiveness in stress of rats from birth to the end of life

The appearance and development of sex difference in the adrenal cortex of rats have been studied. Morphological and secretory differences between the adrenal cortex of female and male rats begin on the 40th day of postnatal life, when females respond in stress by a greater increase in plasma corticosterone concentration. The sex difference becomes fully manifest at the age of 55 days (females have heavier absolute and relative adrenal glands and respond to stressful stimuli by a greater increase in adrenal and plasma corticosterone concentrations). At the age of 11 to 23 months the adrenal corticosterone concentrations in stress are equal in both sexes, and the absolute adrenal weights are similar from 18.5 months until death. The body weight gain is equal in both sexes during the first 50 days of life and greater in males from day 50 to 1 year of age. After this age the body weight of males remains almost the same (315 to 322 g)8 while females continue gaining weight until the end of life (196 to 231 g). This possible causal relationship between the rhythm of growth and sex difference in the adrenal glands in rats is discussed.

Regulation of fetal Na+/K+-ATPase in rat kidney by corticosteroids.

The enzymatic differentiation of various tissues is under hormonal control in the perinatal period. Since the regulation of Na+/K+-ATPase has not been explored prenatally, the aim of this study was to determine the corticosteroid sensitivity of sodium pump maturation in the fetal period. Na+/K+-ATPase activity was both measured in kidney homogenates of fetal rats and localized by in-situ histochemistry. Sodium pump activity was first quantifiable on day 18 of fetal development as 1.4 +/- 0.17 mumol Pi/h per mg protein, and was increased 3.4-times by day 22 of gestation. While the Na+/K+-ATPase activity was the most intense in cortical tubules at an earlier fetal age (18th and 19th day), the reaction product in the medullary tubules increased with fetal age, becoming highly intense on the 21st and 22nd day of gestation. From the 18th to 21st day of fetal development homogenate Na+/K+-ATPase activity increased as a function of chronologic age. While mineralocorticoids were without any effect on Na+/K+-ATPase activity, on the last day of the fetal development, the glucocorticoid dexamethasone proved to be successful in stimulating enzyme activity in corticosteroid-suppressed animals. According to our results, glucocorticoid hormones seem to be operating as an endogenous driving force for sodium pump maturation at the end of fetal development.

Development of steroidogenesis in the fetal rat adrenal gland: An in vitro study ☆

Abstract In vitro synthesis of steroid hormones from [4-14C]-progesterone by the adrenal glands of rat fetuses with various pituitary adrenocorticotropic activities has been investigated. The fetal adrenal glands are capable of synthesizing deoxycorticosterone, corticosterone, 18-hydroxy-11-deoxycorticosterone, 18-hydroxy-corticosterone, 11-dehydrocorticosterone and aldosterone. Adrenal corticosterone synthesis begins on the 14th day of fetal life and continues uninterrupted until delivery. On the 18th day corticosterone synthesis sharply increases, because of the activation of fetal ACTH which induces quantitative changes in fetal steroidogenesis. The yield of radioactive conversion products per unit of fetal adrenal weight decreases during the intrauterine development. The biotransformation of hormones per unit of gland weight depends on the age of fetuses and not on the degree of fetal adrenocorticotropic activity.

Interaction of [3H]-aldosterone with rat kidney plasma membranes

The interaction of [3H]-aldosterone with isolated rat kidney plasma membranes has been studied by centrifugation and gel filtration methods. The Scatchard plot analysis of data indicated the affinity of aldosterone for membrane sites, expressed as equilibrium constant Kdiss, to be 1.3 × 10−8M and the concentration of binding sites (n) 1.69 × 10−13 mol/mg protein. The high concentration of unlabelled aldosterone present in the incubation medium, or injected into rats 45 min before killing, decreased the amount of labelled aldosterone bound to plasma membranes. Gel filtration on Sephadex G-200 and disc electrophoresis on polyacrylamide gel of solubilized [3H]-aldosterone-renal plasma membranes complex showed that the hormone was bound to the high molecular weight protein component of the plasma membranes. The proteinaceous nature of membrane component which bound aldosterone was determined using delipidated plasma membranes.

Feedback Control of Pituitary—Adrenal Activity in Fetus

Publisher Summary This chapter discusses the dependence of growth and functional differentiation of fetal adrenal glands on the weight and secretory activity of the mothers adrenal glands as well as the results of an attempt to determine the quantitative participation of the fetal pituitary in the growth of the fetal adrenal glands. In a study described in the chapter, during the second week of gestation, adrenal weight of the tumor-bearing pregnant rat increased by 52%, and the thymus weight decreased slightly (30%). The last week was characterized by almost four times enlargement of the maternal adrenal glands and a very pronounced thymolytic effect. Adrenal weights of the fetuses increased from the 17th to 21st day of intrauterine development from 0.24 mg to 1.77 mg and were somewhat lighter on the last day (1.70 mg). Adrenal weights of the fetuses from an adrenocorticotropic hormone (ACTH)-secreting tumor-bearing mother also increased, but only from 0.22 mg to 0.64 mg from day 17 to day 21, and 0.76 on the last day of pregnancy. The average daily increase of fetal adrenal weight in mothers with enlarged adrenals was 0.11 mg, which is less than 30% of the daily adrenal weight gain of the control fetuses.

Steroidogenesis of the fetal adrenal gland in vitro: influence of metopirone applied in vivo and in vitro.

Summary In vitro conversion of 4-14C-progesterone into corticosteroids in the adrenal glands of rat fetuses treated with Metopirone (Su 4885) on the last day of intrauterine development was studied. After a 1-hr incubation of the adrenal glands of fetuses injected with Metopirone, hydroxylation of progesterone into corticosterone (B), 18-hydroxycorticosterone (18-OH-B) and 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) decreased and the synthesis of 11-deoxycorticosterone increased. Following preincubation of the fetal adrenal glands and 1-hr incubation with Metopirone, hydroxylation of progesterone into DOC increased and the synthesis of B decreased. Preincubation and a 2-hr incubation with Metopirone caused a decrease in the synthesis of B, 18-OH-B and 18-OH-DOC and an increase in DOC. The results constitute direct evidence of the ability of the fetal adrenal glands to synthesize all corticoids and indicate that most probably corticoids are synthesized by the fetal adrenal glands in the same way as in the adrenals of adult animals.

The effecs of ovarietomy and adrenalectomy on the 5α-reduction of testosterone and corticosterone by female rat tissues in vitro

Abstract The effects ofovariectomy. adrenalectomy and ovariectomy-adrenalectomy on 5α-reduction of testosterone and corticosterone by female rat tissues have been studied. The results suggest that separate enzymes are responsible for 5α-reduction of testosterone and corticosterone. Removal of ovaries or adrenal glands or both had no effect on 5α-reduction of corticosterone by the liver or by pituitary and adrenal glands in vitro . Reduction of testosterone, however, was affected by ovariectomy in all tissues examined and by adrenalectomy in liver tissue. Ovariectomy resulted in an increase in testosterone 5α-reduction by the liver and by pituitary and adrenal glands. Adrenalectomy and ovariectomy-adrenalectomy produced an increase in testosterone 5α-reduction per unit of liver weight, but did not change the capacity of the liver to degrade testosterone, because of the decrease in liver weight caused by adrenalectomy. Adrenalectomy had no effect on testosterone-5α-reduction by the pituitary and ovariectomy adrenalectomy caused the same changes in enzyme activity as ovariectomy alone.

In vitro steroidogenesis of the fetal adrenal glands after dexamethasone administration to pregnant rats

Abstract The in vitro synthesis of corticoids from [4- 14 C] progesterone by the adrenal glands of rat fetuses after treatment of intact and adrenalectomized females with dexamethasone was investigated. Dexamethasone strongly inhibited fetal adrenal growth and fetal adrenal synthesis of corticosterone. Fetal adrenal glands converted [4- 14 C] progesterone to deoxycorticosterone (DOC), corticosterone, 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), 18-hydroxy-corticosterone (18-OH-B) and aldosterone. Dexametha-sone markedly suppressed transformation of [4- 14 C] progesterone in vitro to corticosterone, DOC, and 18-OH-DOC and increased production of 18-OH-B and aldosterone. These results indicate that fetal adrenal growth and fetal adrenal synthesis of DOC, corticosterone and 18-OH-DOC, but not of 18-OH-B and aldosterone, are controlled by fetal ACTH during the last days of intrauterine development.

An in vitro study of sex hormone metabolism in the pituitaries and gonads of neonatal and young rats: the effect of prenatal reduction of litter size

Through incubation with radioactive substrates, the in vitro activity of 17β-dehydrogenase (17-DHG) was studied in the testes of male and the pituitaries of both sexes of rats from birth to the 50th day of life, and the activity of 20 α-dehydrogenase (20-DHG) was studied in the ovaries of developing female rats and in females at parturition. Furthermore, the activities of 5 α-reductase (5-RT) in testes, ovaries and pituitaries were included in the study. The results obtained in rats belonging to litters of normal size (NL: 8–10 pups) were compared to those of small, prenatally reduced litters (RL: 2–5 pups). In both groups a biphasic developmental pattern of testicular 17-DHG activity was found. Maximal activity occurred immediately after birth, and minimal on the 21st postnatal day. In contrast, the activity of testicular 5-RT was low at birth and increased constantly towards the 50th day. Both enzymes were more active in the testes of the RL than in those of the NL rats early neonatally. 20-DHG was inhibited at birth in both NL and RL offspring ovaries. The peak of ovarian activity occured on the 14th day. The ovarian 5-RT activity displayed similar developmental pattern although with higher values. 17-DHG and 5-RT were more active in the pituitaries of the neonatal females than of the males. The male RL rats had smaller 17-DHG pituitary activity than the NL rats in the first three postnatal weeks, whereas the activity of 5-RT immediately after birth was more active in the pituitaries of the NL than in those of the RL females. The difference disappeared shortly after birth.

A simple competitive protein-binding method for determination of progesterone in the rat plasma.

Abstract Acetylation of the hydroxyl group in 20α-hydroxy-4--pregnen-3-one decreases the binding capacity of the molecule to transcortin to only 1% of that of progesterone. By this simple procedure it is possible to eliminate the influence of 20α-hydroxy-4-pregnen-3-one in determinations of progesterone concentrations by the competitive protein--binding method, which is highly desirable when a great number of samples are analyzed.