Relation of the testis to adrenal enzyme activity and adrenal corticosterone production in the rat

Invited review: Adrenocortical function in avian and non-avian reptiles: Insights from dispersed adrenocortical cells

Herein we review our work involving dispersed adrenocortical cells from several lizard species: the Eastern Fence Lizard (Sceloporus undulatus), Yarrow's Spiny Lizard (Sceloporus jarrovii), Striped Plateau Lizard (Sceloporus virgatus) and the Yucatán Banded Gecko (Coleonyx elegans). Early work demonstrated changes in steroidogenic function of adrenocortical cells derived from adult S. undulatus associated with seasonal interactions with sex. However, new information suggests that both sexes operate within the same steroidogenic budget over season. The observed sex effect was further explored in orchiectomized and ovariectomized lizards, some supported with exogenous testosterone. Overall, a suppressive effect of testosterone was evident, especially in cells from C. elegans. Life stage added to this complex picture of adrenal steroidogenic function. This was evident when sexually mature and immature Sceloporus lizards were subjected to a nutritional stressor, cricket restriction/deprivation. There were divergent patterns of corticosterone, aldosterone, and progesterone responses and associated sensitivities of each to corticotropin (ACTH). Finally, we provide strong evidence that there are multiple, labile subpopulations of adrenocortical cells. We conclude that the rapid (days) remodeling of adrenocortical steroidogenic function through fluctuating cell subpopulations drives the circulating corticosteroid profile of Sceloporus lizard species. Interestingly, progesterone and aldosterone may be more important with corticosterone serving as essential supportive background. In the wild, the flux in adrenocortical cell subpopulations may be adversely susceptible to climate-change related disruptions in food sources and to xenobiotic/endocrine-disrupting chemicals. We urge further studies using native lizard species as bioindicators of local pollutants and as models to examine the broader eco-exposome.

Endogenous testosterone reduces hepatic lipid accumulation in protein-restricted male rats

OBJECTIVES

Protein deficiency is known to cause ectopic fat accumulation in the liver. The aim of this study was to analyse the mechanism of suppression of hepatic fat accumulation by testosterone and to clarify the mechanism behind the gender difference in fatty liver formation due to protein deficiency.

METHODS

Hepatic fat accumulation due to protein deficiency was evaluated in male and female rats before and after sexual maturation. Then, the effects of testosterone on liver lipid, muscle protein metabolism and energy expenditure in adipose tissue were investigated in castrated or testosterone-injected male rats fed control or protein-restricted diet.

RESULTS

Hepatic triglyceride accumulation diminished with sex maturation in male but not in female protein-restricted rats. Protein restriction resulted in a significant increase in hepatic triglyceride content in castrated rats but not in sham-operated rats demonstrating that endogenous testosterone reduces hepatic lipid accumulation in male rats. Protein restriction reduced plasma IGF-I and muscle protein synthesis measured using the SUnSET method. Castration increased the plasma corticosterone level and muscle autophagic activity. Muscle weight was reduced and energy expenditure in adipose tissue was increased only when both factors were combined.

CONCLUSIONS

Muscle protein synthesis downregulation owing to protein restriction and activation of autophagy following castration reduced muscle mass thereby releasing surplus energy and promoting steatosis in protein-restricted castrated rats despite increased energy expenditure in adipose tissue. We hypothesize that endogenous testosterone reduces hepatic lipid accumulation in protein-deficient male rats and provide novel findings on the gender-specific differences in hepatic steatosis.

Postnatal blockade of androgen receptors or aromatase impair the expression of stress hypothalamic-pituitary-adrenal axis habituation in adult male rats

Sex steroid hormones during development permanently alter, or organize, the brain and behavior, while during adulthood they act to reversibly modulate, or activate, physiology and behavior. Testosterone exerts both organizational and activational effects on the magnitude of the hypothalamic-pituitary-adrenal (HPA) axis response to acute stress. What has never been approached is how testosterone can organize habituation of the HPA axis, in which stress induced elevations in ACTH and corticosterone release decline over repeated exposures to the same stimulus. In the current study we examined HPA responses to repeated psychogenic stress in 65-day-old, adult male rats that received subcutaneous capsules containing the antiandrogen flutamide or the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD), introduced within 12h of birth and removed on day 21 of weaning. An additional group of castrated, adult male rats were used to differentiate organizational from activational effects of testosterone. All treatment groups displayed smaller declines in ACTH in response to repeated restraint compared to control animals. Remarkably, the normal decline in corticosterone failed to occur in flutamide- and ATD-treated animals. By contrast, males that were castrated as adults showed a significant reduction in corticosterone after repeated stress. Taken together, these findings underscore an organizing influence of both androgen receptors and estrogen conversion on HPA habituation to repeated psychogenic stress, which appears to occur independent of the activational effects of testosterone.

Gonadal modulation of in vitro steroidogenic properties of dispersed adrenocortical cells from Sceloporus lizards

Effects of adrenal corticosteroids on reproductive and endocrine functions of the gonads are well known, but reciprocal effects of gonadal hormones on the hypothalamo-pituitary-adrenal (HPA) axis and on adrenocortical steroidogenesis in particular have received much less attention. We investigated effects of gonadectomy and testosterone (T) replacement on adrenocortical cell function in a year-long field study of male Sceloporus undulatus (Eastern Fence Lizard) and in a shorter term laboratory study with male Sceloporus jarrovii (Yarrow's Spiny Lizard). We also compared females to males in Sceloporus virgatus (Striped Plateau Lizard) and investigated effects of gonadectomy in short-term laboratory experiment on females of this species. As measured by in vitro production of progesterone (P(4)), corticosterone (B), and aldosterone (ALDO), sensitivity of adrenocortical cells to corticotrophin (ACTH) was lower in control males than females of S. virgatus. In S. jarrovii males, cellular sensitivity to ACTH was reduced by orchiectomy but was not restored to levels of intact controls by T replacement. By contrast, in S. undulatus, cellular sensitivity to ACTH was not affected by orchiectomy alone but was reduced by T replacement in orchiectomized males. Maximal rates of steroid production were less consistently affected by experimental treatments, but were lower in males than in females of S. virgatus and were dramatically reduced by T replacement in orchiectomized S. undulatus males. Overall, our experiments clearly demonstrate two distinct sources of variation in functional capacities of dispersed adrenocortical cells isolated from Sceloporus lizards: (1) naturally occurring differences between males and females (Carsia and John-Alder, 2003), and (2) species-dependent changes in response to surgical gonadectomy with or without exogenous testosterone. Sex differences and functional lability in adrenocortical cells are probably widespread among vertebrates and may be an important component of variation in output of the HPA.

Prolactin induces adrenal hypertrophy

Although adrenocorticotropic hormone is generally considered to play a major role in the regulation of adrenal glucocorticoid secretion, several reports have suggested that other pituitary hormones (e.g., prolactin) also play a significant role in the regulation of adrenal function. The aim of the present study was to measure the adrenocortical cell area and to determine the effects of the transition from the prepubertal to the postpubertal period on the hyperprolactinemic state induced by domperidone (4.0 mg kg-1 day-1, sc). In hyperprolactinemic adult and young rats, the adrenals were heavier, as determined at necropsy, than in the respective controls: adults (30 days: 0.16 +/- 0.008 and 0.11 +/- 0.007; 46 days: 0.17 +/- 0.006 and 0.12 +/- 0.008, and 61 days: 0.17 +/- 0.008 and 0.10 +/- 0.004 mg for treated and control animals, respectively; P < 0.05), and young rats (30 days: 0.19 +/- 0.003 and 0.16 +/- 0.007, and 60 days: 0.16 +/- 0.006 and 0.13 +/- 0.009 mg; P < 0.05). We selected randomly a circular area in which we counted the nuclei of adrenocortical cells. The area of zona fasciculata cells was increased in hyperprolactinemic adult and young rats compared to controls: adults: (61 days: 524.90 +/- 47.85 and 244.84 +/- 9.03 microm2 for treated and control animals, respectively; P < 0.05), and young rats: (15 days: 462.30 +/- 16.24 and 414.28 +/- 18.19; 60 days: 640.51 +/- 12.91 and 480.24 +/- 22.79 microm2 ; P < 0.05). Based on these data we conclude that the increase in adrenal weight observed in the hyperprolactinemic animals may be due to prolactin-induced adrenocortical cell hypertrophy.

Changes in the expression of steroid metabolism-related genes in rat adrenal glands during selective REM sleep deprivation

Selective REM sleep deprivation was carried out under the conditions designed to minimize the adverse influence of environmental conditions and restricted movement, and the influence of REM sleep deprivation on adrenocortical steroid metabolism was investigated by measuring the steady-state levels of mRNAs encoding steroid metabolism-related genes, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme cytochrome P450 (P450scc) and steroid 5alpha-reductase (5alpha-R), in rat adrenal glands. Selective REM sleep deprivation caused a significant decrease in StAR mRNA and an increase in 5alpha-R mRNA levels without any notable change in P450scc mRNA levels in the adrenal gland. In contrast, non-selective sleep disturbance, resulting in the partial reductions of non-REM and REM sleep, tended to increase both StAR and P450scc mRNA levels without any statistical significance. These results indicate that REM sleep deprivation by itself may affect the expression of steroid metabolism-related genes in the adrenal gland, suggesting a possible relation between REM sleep and adrenocortical steroid metabolism.

Effect of copper chloride on adrenocortical activities in adult and immature male rats

Although copper is an important biological trace element required for normal metabolism, occupational exposure to copper in different industrial workers may result in abnormal rise in plasma copper level which can bring about adverse effects. Intraperitoneal injection of copper chloride at the dose of 2000 μg/kg per day and higher doses for 26 days resulted in significant rise in adrenal weight, adrenal Δ(5)-3β hydroxysteroid dehydrogenase (HSD) activity and serum corticosterone level in both adult and immature male rats, while 1000 μg/kg per day dose for 26 days duration did not significantly alter the adrenocortical activities and adrenal weight in adult rats. On the contrary, the latter lower dose caused a significant decrease in adrenal Δ(5) 3β HSD activity and serum corticosterone level in immature male rats.

Ontogeny of the sex steroid and prolactin receptors in the male rat adrenal gland

Cytosolic estrogen and androgen receptors and membrane prolactin-binding sites in the male adrenal glands showed a definite pattern during sexual development. The level of sexual steroid receptors paralleled adrenal growth, whereas prolactin binding reached its maximum value in mature rats.

Effects of age at vasectomy on corticosterone production by the rat testes

The ability of the testicular interstitium to assume a certain degree of adrenocortical-like activity, and the concomitant changes in adreno-gonadal status, 100 days post-vasectomy, were investigated in rats (50 and 150 days of age, at start). The transformation of 11-deoxycorticosterone (1,2-H3) to corticosterone (1,2-H3), by the testicular homogenates, was used as an index of 11 beta-steroid hydroxylase activity in the Leydig cells. The extent of ascorbic acid depletion in the adrenals and testes, and the plasma and testicular levels of corticosterone, were assayed, to examine the adreno-testicular participation in corticosteroidogenesis. Vasectomy in younger rats, as compared to older rats, resulted in a significant increase in the transformation of deoxycorticosterone to corticosterone, and higher plasma corticosterone levels. It appears that vasectomy, at a younger age, is capable of inducing adrenocortical-like activity in the testicular interstitium.