Androgenic control of N-acetyltransferase activity in the harderian glands of the Syrian hamster is mediated by 5 alpha-dihydrotestosterone

N-acetyltransferase (NAT) activity in the Harderian glands of intact and gonadectomized male and female Syrian hamsters was evaluated. The exogenous administration of 5 alpha-dihydrotestosterone (DHT) to castrated males and intact females produced an increase in NAT values, which reached the values present in the glands of intact males. The administration of a 5 alpha-reductase inhibitor to intact males led to a decrease in NAT activity, suggesting that testosterone is converted in DHT within the glands. It is concluded that NAT activity in the Syrian hamster Harderian glands is under androgenic control, the active steroid being DHT.     

Bromocriptine prevents the castration-induced rise in porphyrin concentration in the harderian glands of the male Syrian hamster, Mesocricetus auratus

The Harderian glands in Syrian hamsters exhibit a striking sexual dimorphism. Male Harderian glands show two cell types and low levels of porphyrins and melatonin. Of the enzymes involved in the synthesis of melatonin, N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) show high and low activity levels, respectively. Female Harderian glands show but one cell type and have high porphyrin and melatonin levels, low NAT activity, and high HIOMT activity. In castrated males, the Harderian glands exhibit a female pattern of morphology, porphyrin levels, and indoleamine metabolism. In an attempt to determine whether prolactin in involved in this sexually dimorphic response of the Harderian glands, intact and castrated male and intact female hamsters were injected daily with 500 micrograms of bromocriptine, a dopamine agonist. Bromocriptine led to reduced serum prolactin levels in all groups. It had no apparent effect on the Harderian glands of intact males. In contrast, in castrated males bromocriptine prevented the postcastrational rise in porphyrin levels but had no effect on NAT or HIOMT activities. In females, bromocriptine treatment had no effect on porphyrin concentrations or HIOMT activity; it led to a statistically significant increase in NAT activity. We propose that testosterone inhibits Harderian porphyrin synthesis while dopamine or prolactin stimulates it.     

Effects of inhibition of thyroid function and of cold on melatonin synthesis and porphyrin content in the Harderian glands of male Syrian hamsters, Mesocricetus auratus

1. Indole metabolism and porphyrin content of the Harderian glands of the male Syrian hamster were measured as functions of drug-induced hypothyroidism and exposure to cold conditions. 2. Harderian gland N-acetyltransferase (NAT) activity was reduced from control levels by hypothyroidism induced by methimazole; exposure to cold had no effect on NAT activity. 3. Immunoreactive melatonin in the Harderian glands was unaffected by the state of thyroid secretion. However, immunoreactive melatonin content declined after 180 and 270 min, at 4 degrees C, suggesting that Harderian gland melatonin may be involved in thermoregulation. 4. Porphyrin content of the Harderian glands was not affected by either thyroid secretion or cold.     

Effects of prepubertal manipulation with androgens on the development of sexual differences in the harderian glands of Syrian hamsters.

The onset of sexual differences in the metabolism of porphyrins and melatonin in the Harderian glands of Syrian hamsters was studied. Three weeks after birth, the porphyrin concentrations were already higher in glands of females than in those of males. Castration of 22-day-old male hamsters led to an increase in Harderian porphyrin concentrations, although the levels of intact females were not reached. The administration of testosterone to 22-day-old female hamsters resulted in a marked decrease in porphyrin concentrations. Study of the development of sexual differences in the enzymes involved in melatonin synthesis, N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) indicated that not all the sexual differences observed in these glands begin at the same time. Thus, while differences in NAT activity were detected after the age of 3 weeks, male-female differences in HIOMT activity were only observed after 7 weeks. Castration of prepubertal male hamsters lowered NAT but not HIOMT activities. The administration of testosterone to prepubertal female hamsters led to male activity levels in both enzymes. Although circulating androgens seem to have a crucial role in maintaining sexual differences, other hormones including those from the pituitary and thyroid glands are probably also important for generating these sexual differences.     

Development and androgen regulation of the secretory cell types of the Syrian hamster (Mesocricetus auratus) Harderian gland

The secretory cell types of the hamster Harderian glands were studied in both male and female Syrian hamsters. As previously demonstrated, female hamsters showed a single secretory cell type (type I), while male hamsters displayed two secretory cell types (type I and type II). Type-II cells were observed after the first month of age correlating with the increase in testosterone levels. The administration of testosterone to adult female hamsters resulted in a marked increase in the percentage of type-II cells without a significant increase in the number of mitotic figures. Very low levels of serum testosterone were able to maintain the percentage of type-II cells. Castration of male hamsters produced a decrease in the percentage of type-II cells. This drop correlated with the reduction in serum testosterone levels. The chronic administration of a luteinizing hormone-releasing hormone agonist to male Syrian hamsters induced a significant reduction in both serum luteinizing hormone and testosterone. However, the percentage of type-II cells was similar to that of control hamsters suggesting that very low levels of circulating testosterone are able to maintain the percentage of type-II cells. In a final experiment male Syrian hamsters were treated with the antiadrogen cyproterone acetate. No changes were observed in the percentage of type-II cells, whereas serum luteinizing hormone and testosterone levels were significantly modified. We concluded that (1) type-II cells differentiate from type-I cells; (2) gonadal androgens are the major factor controlling this differentiation; and (3) the disappearance of type-II cells after androgen deprivation occurs through holocrine and apocrine mechanisms. The possible implication of 5-reductase in the regulation of secretory cell types in the Harderian glands of hamsters is discussed.     

The effects of bromocriptine and prolactin on porphyrin biosynthesis in the Harderian gland of the male hamster,Mesocritecus auratus

Porphyrin biosynthesis was examined in the Harderian gland of the male golden hamster by fluorometric assays of gland porphyrin content and by measuring the activity of a rate-limiting enzyme for haem biosynthesis, 5-aminolaevulinic acid synthase. Both porphyrin content and enzyme activity are low in normal male glands but were greatly raised in males castrated for 6 weeks. However, porphyrin synthesis remained at basal levels in castrates given the dopamine agonist bromocriptine; this suppression could be reversed by simultaneous prolactin administration, and castrated males receiving prolactin alone exhibited very high enzyme activity and porphyrin content. Bromocriptine also prevents the morphological feminisation of the Harderian gland which would normally occur after castration; again, the simultaneous administration of prolactin permits feminisation to occur. The results support the hypothesis that, while androgens have an inhibitory effect on porphyrin synthesis within this model, other factors, including prolactin, are permissive.Abbreviations ALA 5-aminolaevulinic acid - ALA-s 5-aminolaevulinate synthase - GH growth hormone     

Harderian gland: regulation of sexual "type" by gonads and pineal gland

The sexual dimorphism of the Harderian glands of golden hamsters is regulated by a complex interaction of the gonads and pineal gland. Ovariectomy was shown to prevent the conversion to male-type gland which normally follows blinding. Testosterone administration in combination with blinding and ovariectomy promoted the male type. Ovariectomy after 8 wk of blinding was ineffective in reversing the effects of blinding on the Harderian glands, but ovariectomy and pinealectomy caused complete reconversion to the female type. To our knowledge, this is the first report to demonstrate an influence of the ovaries on the Harderian gland of the hamster. In males, administration of testosterone for 7 days after 8 wk of castration was shown to have little effect on the conversion to the female type which normally attends castration, whereas testosterone injection followed by a period of blinding completely reversed the effects of castration on the Harderian gland. These studies, along with previously published reports, strongly suggest that the male-type Harderian gland is expressed whenever significant androgen levels are present, or when the glands are exposed to androgen priming during or just prior to a period of blinding-induced pineal activation. The probable role of ovarian androgens in mediating conversion to the male-type gland is discussed.     

Effects of human chorionic gonadotropin and progesterone administration on porphyrin biosynthesis and histology of the Harderian glands in male and female Syrian hamsters.

We investigated the influence of hCG and progesterone on the control of porphyrin biosynthesis and histology in the Syrian hamster Harderian glands. Castration of male hamsters caused a marked elevation in porphyrin biosynthesis as revealed by the concentrations of porphyrins and the mRNA levels of the porphyrin pathway rate-limiting enzyme, 5-aminolevulinate synthase (ALV-S). Injection of hCG into castrated male hamsters also resulted in a significant increase in both porphyrin concentrations and levels of ALV-S mRNA compared with those in saline-injected castrated hamsters. Type II cells, which are filled with large lipid vacuoles and are characteristic of male phenotype, disappeared after castration, but administration of hCG partially prevented this change. On the other hand, neither administration of hCG nor progesterone implants could increase the very high porphyrin concentrations and ALV-S mRNA levels characteristic of female Syrian hamsters. As in the case of castrated male hamsters, injections of 20 IU hCG to female Syrian hamsters increased the relative number of Type II cells per square millimeter, whereas progesterone administration did not modify the relative number of Type II cells. These results indicate that hCG can modify Harderian gland morphology in both male and female hamsters and can exert a positive control in the expression of ALV-S gene in castrated male hamsters.     

Characteristics of the androgenic function of steroid-producing glands of baboons in the metapyrone test

Experiments on adult and prepubertal male baboons were made to study and compare the androgenic function of the steroid-producing glands of monkeys in the metopyrone test. The content of the steroid compounds, testosterone, 5 alpha-dihydrotestosterone, delta 4-androstendione and dehydroepiandrosterone in the monkey blood was measured by radioimmunoassays. The content of 5 alpha-dihydrotestosterone in the blood of monkeys of both age groups did not undergo any significant changes throughout the whole experiment, whereas the content of testosterone and delta 4-androstendione rose to a greater degree in the blood of prepubertal animals. The concentration of dehydroepiandrosterone in the blood of prepubertal monkeys remained significantly elevated, even 3 days after the metopyrone administration. The reasons for age-associated differences in the hormonal response of the steroid-producing glands of baboons to metopyrone administration are discussed.     

Gender differences and time course of castration-induced changes in porphyrins, indoles, and proteins in the Harderian glands of the Syrian hamster.

Sexual differences and the effects of orchidectomy were determined for porphyrin and melatonin concentrations and for the activities of the enzymes N-acetyltransferase and hydroxyindole-O-methyltransferase, which synthesize melatonin from serotonin, in the Harderian glands of the Syrian hamster. Porphyrin concentrations in intact males were about 1/400th those of intact females. Castration for 1 week increased male Harderian porphyrin concentrations 10-fold; by 3 weeks, castrated male porphyrin levels were 140 times those of control values. N-Acetyltransferase activity in intact male Harderian glands was about 4 times that of females. Castration led to a drop in N-acetyltransferase activity to female levels within 2 weeks. Hydroxyindole-O-methyltransferase activity was 7 times higher in females than in males and castration had no effect on male Harderian hydroxyindole-O-methyltransferase activity. Neither gender nor castration influenced Harderian melatonin concentrations. Soluble proteins in Harderian glands from male and female hamsters and from male hamsters castrated for 1 and 4 weeks were examined by sodium dodecyl sulfate--polyacrylamide gel electrophoresis. The gel profiles revealed several differences among the protein distribution in male and female gland lysates. Orchidectomy led to a female protein pattern within 4 weeks.     

The effects of gonadectomy and testosterone treatment on the Harderian gland of the green frog,Rana esculenta

The effects of gonadectomy and testosterone treatment on the fine structure of the Harderian gland in male and female green frogs were investigated in different periods of the year. Gonadectomy, carried out when the glands are in the lowest secretory phase (September), causes degenerative changes consisting of a reduction of the rough endoplasmic reticulum, the appearance of autolysosomes, and an increase of nuclear heterochromatin. These effects can be prevented by testosterone treatment. No castration effects are found during the recovery (November) and enhancement (April-May) phases of secretory activity. The results suggest that the frog Harderian gland's sensitivity to testosterone changes during the annual cycle. The androgen dependence of the Harderian gland is correlated with the presence of androgen receptors in both male and female forgs.     

Melatonin and porphyrin in the harderian glands of the Syrian hamster: circadian patterns and response to autumnal conditions

1. Adult male Syrian hamsters were killed at nine intervals during a 24 hr period in the autumn, after 2 months either indoors in controlled conditions or in natural outdoor conditions. 2. Harderian glands were taken for determination of N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities and melatonin and porphyrin concentrations. 3. Mean 24 hr Harderian NAT and melatonin values were lower outside than inside. 4. Twenty-four hour melatonin rhythms were detected with similar daytime (afternoon) acrophases in both environmental conditions. 5. An NAT rhythm was seen only in animals kept inside, with a circadian maximum in the late dark phase. 6. Mean 24 hr HIOMT activity was slightly higher outdoors than indoors, and 24 hr rhythms were not detected in either condition. 7. Mean porphyrin concentrations were higher outdoors, with 24 hr rhythms detected in both conditions and a significantly earlier nocturnal circadian maximum outdoors.     

Testosterone increases N-acetyltransferase activity in both male and female Syrian hamster harderian glands

N-acetyltransferase (NAT) activity was studied in the Harderian glands of intact and castrated (with or without subcutaneous testosterone implants) male and female Syrian hamsters. Castration in male hamsters produced a significant drop in the NAT activity. Castrated males with testosterone implants had NAT activity levels comparable to those in intact males. Ovariectomy did not modify NAT activity. Ovariectomized hamsters with testosterone implants exhibited a significant increase in the Harderian NAT activity reaching the same values as those in the glands of the male hamsters.     

N-acetyltransferase activity and indole contents of the male Syrian hamster Harderian gland: changes during the light:dark cycle

The activities of N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) and the indole contents of the Harderian glands of male Syrian hamsters were studied throughout a 24-h period. NAT activity exhibited a sharp rise 1 h after lights on, decreasing to basal levels 1 h later. Neither a HIOMT activity nor a melatonin concentration rhythm was detected throughout the 24 h. The 5-hydroxytryptamine (serotonin) concentration was highest during the dark phase reaching a peak at 0300 h; with light onset serotonin levels exhibited a rapid short-term drop. The 5-hydroxytryptophol concentration was highest during the mid- to late photophase; the lowest values to this constituent were measured late in the dark phase and at 1 h after lights on. The 5-hydroxyindole acetic acid concentration of the Harderian glands was rather stable throughout the 24-h period but levels did show a short-lived drop 1 h after light onset. Only a few animals contained detectable amounts of N-acetyl-5-hydroxytryptamine (N-acetylserotonin) in their Harderian glands. In agreement with previous work on the Harderian glands of female Syrian hamsters, the present results in males suggest that light onset is associated with marked changes in Harderian indoleamine metabolism.     

Response of the epididymis, ductus deferens & accessory glands of the castrated prepubertal rhesus monkey to exogenous administration of testosterone or 5alpha-dihydrotestosterone.

The response of the epididymis, ductus deferens, and accessory glands of the castrated prepubertal rhesus monkey to exogenous administration of testosterone or 5alpha-dihydrotestosterone (DHT) was investigated. 200 or 800 mcg of either steroid/day were administered for 60 days beginning on the day after castration. Castration caused a marked regression of the weight of and secretory function of the reproductive organs; testosterone/DHT stimulated their growth and secretory activity which were maintained at the level of the controls. The weight of the caput epididymides however, was unaffected by testosterone but was stimulated by DHT. DHT caused a greater stimulation of the growth and secretory activity of the reproductive organs than testosterone and also caused a hyperstimulation of secretion by the seminal vesicles. The data, analyzed statistically, show that the accessory organs of the prepubertal rhesus monkey are affected by castration and vary in their response to stimulation by exogenous androgens.     

Sexual dimorphism in N-acetyltransferase activity, hydroxyindole-O-methyltransferase activity, and melatonin content in the Harderian gland of Syrian hamsters: changes following gonadectomy

The activities of N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) and the melatonin content of the Harderian glands of intact and gonadectomized male and female Syrian hamsters were studied. NAT activity in intact male Harderian glands was twice that of the female. Prepubertal or adult castrated males exhibited a decrease in NAT activity to a level comparable to that seen in the female. Testosterone implants in the castrated males led to a recovery of the original male NAT levels. Intact male hamsters had very low levels of Harderian HIOMT activity and melatonin content in comparison with the glands of the females. Prepubertal gonadectomy but not castration of adult males raised the levels of HIOMT activity and the melatonin content to those of the females. Bilateral ovariectomy had no effect on melatonin content, NAT activity, or HIOMT activity in the female hamster Harderian gland.     

N-acetyltransferase activity, hydroxyindole-O-methyltransferase activity, and melatonin levels in the Harderian glands of the female Syrian hamster: changes during the light:dark cycle and the effect of 6-parachlorophenylalanine administration

The activities of NAT and HIOMT and the melatonin content of the Harderian glands of female Syrian hamsters were studied. When hamsters were kept under a light:dark cycle of 14:10 (lights on at 06.00 h), NAT activity exhibited a sharp, short term rise at one hour after lights on. Simultaneously, the activity of HIOMT, which forms melatonin, exhibited a rapid decline. Melatonin levels, like HIOMT activity, also showed a precipitous drop at one hour after light onset. After the respective changes, both NAT and HIOMT activity reverted back to night time levels. Melatonin levels remained depressed for several hours but by 1400 h (8 hours after lights on), nighttime melatonin values were re-established. Treatment of female hamsters with PCPA, a trytophan hydroxylase inhibitor, led to depressed levels of Harderian melatonin without affecting the activities of either NAT or HIOMT.     

Effect of testosterone on the female hamster harderian gland pigmentation and ultrastructure

Summary Distinct differences occur in the pigmentation and ultrastructural features of the Harderian glands in male and female hamsters. The results of a study on the effect of testosterone on the fine structure of the female Harderian glands are presented here. Glands from three groups of hamsters were examined at intervals up to 49 days: (1) testosterone injected, receiving 2mg testosterone propionate in 0.1 ml sesame oil per day; (2) sham-injected, receiving 0.1 ml sesame oil per day; (3) untreated controls. Testosterone injections caused a reduction in the number of dark-brown pigment granules in the acinar cells starting on the 6th day, whereas clusters of tubules, typical of adult male glands, appeared on the 4th day and increased in number thereafter. Lamellar structures, normally present in the female gland, decreased in testosterone treated specimens. These changes reversed after cessation of testosterone treatment. It is concluded that exogenous testosterone administered to female hamsters modifies the pigmentation and ultrastructure of their Harderian glands towards the male type and that this is a reversable phenomenon. There also appears to be an inverse relationship between the presence of tubular clusters in the acinar cells, and the degree of pigmentation.     

Immediate postnatal rise in whole body androgen content in male rats: correlation with increased testicular content and reduced body clearance of testosterone

Whole body content of androgen (testosterone + 5 alpha-dihydrotestosterone) was invariably higher in male than in female rat pups killed 1 or 3 h after natural delivery, whereas androgen content was equivalent in males and females killed immediately or 6, 12, and 24 h after birth. Testicular content of androgen was significantly elevated in males killed 1 and 24 h after birth, compared with levels in males killed immediately, or 3, 6, and 12 h after birth. Thus, heightened testicular androgen content was only initially associated with increased systemic levels of androgen in males during the immediate postpartum period. A second study assessed the possibility that the body's clearance (i.e., metabolism plus excretion) of testosterone is lower in newborn rats upon separation from the placental circulation than in slightly older pups. Rats of both sexes killed 1 and 3 h after s.c. injection of [3H] testosterone had significantly higher plasma concentrations of [3H] testosterone as well as several 5 alpha-reduced androgens (5 alpha-dihydrotestosterone, 3 alpha-androstanediol, and androsterone) when injections were given within minutes as opposed to 24 h after birth. This suggests that in both sexes the clearance of testosterone is slower immediately after birth than at later ages. This phenomenon together with a brief postnatal elevation in the testicular synthesis and secretion of testosterone may explain the temporary rise in circulating androgen concentrations that occurs in the newborn male rat.     

Endocrine profile of Win 49596 in the rat: a novel androgen receptor antagonist

Win 49596 is a new orally active, steroidal androgen receptor antagonist. Win 49596 inhibited ventral prostate, seminal vesicle and levator ani weight gain in either 5 alpha-dihydrotestosterone (DHT) or testosterone propionate-treated castrated, immature male rats. In intact, adult male rats, Win 49596 significantly inhibited weight gain by the ventral prostate, dorsal lateral prostate and seminal vesicles, but not the testes at doses as low as 50 mg/kg/day x 14 p.o. However, daily oral administration of equivalent antiandrogenic doses of either Win 49596, ICI 176,334, or flutamide for 14 days to mature, intact male rats resulted in elevations of circulating testosterone of approximately 3-, 2-, and 10-fold, respectively. At doses as high as 400 mg/kg p.o., Win 49596 did not have androgenic, progestational, estrogenic or antiestrogenic activity in rat or rabbit models. However, in the Clauberg assay, Win 49596 did have weak antiprogestational activity at doses of 25-400 mg/kg/day p.o. These data indicate that Win 49596 is a peripherally selective antiandrogen that has minimal effects on circulating testosterone levels and is devoid of hormone agonist activity. Thus, Win 49596 may be useful for the treatment of androgen dependent conditions such as benign prostatic hyperplasia and prostatic cancer.