Effect of the photoperiod in modulating the androgenic control of 1-alkyl-2,3-diacylglycerol composition in the harderian gland of the golden hamster, Mesocricetus auratus.

The golden hamster Harderian gland produces a lipid secretion consisting mainly of 1-alkyl-2,3-diacylglycerol. We investigated the composition of alkyl and acyl groups in male and female hamster Harderian alkyldiacylglycerol, in animals kept in long and short photoperiods. Female hamsters in long days have alkyl groups with long saturated straight chains (C18:0 and C20:0) and methyl-branched chains (even and odd chain length iso-branched and odd chain length anteiso-branched chains). Acyl groups in females in long days are mostly long straight chains (C16:0) and methyl-branched chains. In females, short photoperiods led to reductions in the proportions of methyl-branched chains and changes in the proportions of straight chain alkyl and acyl groups; these changes were prevented by pinealectomy. Male hamsters with intact gonads, maintained in long days, had no methyl-branched chain alkyl or acyl groups; saturated straight chains were generally shorter than those of females and the odd chain length saturated C15:0 acyl group was common. Short photoperiods did not significantly alter the composition of male alkyldiacylglycerol. Castrated male hamsters in long days showed a distinctively female phenotype, with long straight chains and methyl-branched alkyl and acyl groups. Castrated males in short days showed a mixture of male and female characteristics: shorter straight chain alkyl and acyl groups, a total absence of methyl-branched alkyl groups, and the presence of methyl-branched acyl groups. These results and those of other studies suggest that testosterone controls the enzymes isovaleryl acyl-CoA dehydrogenase and 2-methyl branched-chain acyl-CoA dehydrogenase; in the absence of these enzymes, the primers for the synthesis of methyl-branched chain fatty acids are produced. Our results indicate that this control is modulated by short photoperiods (perhaps due to reduced prolactin levels). It is also suggested that characteristics of male-type alkyldiacylglycerol are better adapted to conditions of autumn and winter than are those of female-type alkyldiacylglycerol.

Sexual differences in 5'-deiodinase activity in the Harderian gland of Syrian hamsters and the effect of pinealectomy: regulation by androgens.

Sexual differences on thyroxin 5'-deiodinase (5'-D) in the Harderian gland of Syrian hamsters were investigated. We compared the 24-h profile of 5'-D activity in male and female hamsters, observing a clear rhythm in males but not in females. Female values were always significantly higher than male ones. After pinealectomy day/night variations in male 5'-D activity at the time points studied were abolished, results that are in correlation with serum thyroid hormones. We also studied the regulation by androgen of the enzyme activity. Basal 5'-D activity increased in castrated males and levels fell when animals were implanted with testosterone or its product 5 alpha-dihydrotestosterone (DHT). Female 5'-D activity was also inhibited by androgens. As only the addition of DHT in the presence of epitestosterone, an inhibitor of the conversion of testosterone on DHT, in castrated males was able to decrease 5'-D activity to the control animal levels, we suggest a probable direct effect of DHT by itself.

Melatonin levels in idiopathic scoliosis. Diurnal and nocturnal serum melatonin levels in girls with adolescent idiopathic scoliosis.

STUDY DESIGN: Matched pairs of adolescent girls were used to compare serum melatonin levels in adolescent patients and control subjects with idiopathic scoliosis during the day and in the middle of the night. OBJECTIVES: To compare serum melatonin levels in patients with adolescent idiopathic scoliosis and matched control subjects during the day and in the middle of the night. SUMMARY OF BACKGROUND DATA: Recent studies using the chick as the animal model have suggested that the pineal gland and its main product, melatonin, might be involved in the cause of scoliosis. There have been no studies of melatonin levels in patients with adolescent idiopathic scoliosis. METHODS: Blood was collected from seven adolescent girls with idiopathic scoliosis and a group of seven age-matched control subjects. Two samples were collected, one in the middle of the day and one in the middle of the night, to examine the diurnal variation of melatonin production. Serum melatonin levels were measured using a radioimmunoassay technique. RESULTS: No significant differences were found in serum melatonin levels between experimental and control groups either during the day, when melatonin levels were low, or during the night, when melatonin levels were high. CONCLUSIONS: Whereas pinealectomy in young chickens leads to reduced melatonin levels and the development of scoliosis, the results of this study suggest that melatonin levels in mature patients who already have severe scoliosis do not differ from healthy subjects. Whether melatonin levels differ in humans between healthy subjects and patients with scoliosis at the time of onset of the disease remains to be seen.

Sexual dimorphism in the harderian gland of the Syrian hamster is controlled and maintained by hormones, despite seasonal fluctuations in hormone levels: functional implications.

The Harderian gland of the Syrian hamster (Mesocricetus auratus) is unusual amongst rodents in the degree of dimorphism present. Other types of hamsters have Harderian glands which are apparently identical in male and female animals. Laboratory populations of Syrian hamsters are derived from very limited genetic stock, which makes one concerned lest they not be representative of wild populations; however, until wild stocks of M. auratus become available, we should assume that insights derived from studies of dimorphism in Syrian hamsters represent important considerations for the life of these animals. Two dimorphic features are the histology and the porphyrin content of the Harderian glands. About 95% of the lipid droplets in female glands are small (type 1), whereas only about 65% of those in males in type 1, with the other 35% being type 2 (large droplets). Five weeks of castration of males led to an increase in type 1 droplets to 90%. On the other hand, 2 weeks treatment of females with testosterone led to a reduction in type 1 droplets to about 82%. Short day photoperiods led to a large increase in type 2 droplets in both males and females (to 52% in males, 35% in females after 8 weeks). These results suggest that the lipid contained in type 2 droplets is important to hamsters of both sexes during the winter. Porphyrin concentrations are 100-1,000 times higher in females than males, and this is largely controlled by testosterone as orchidectomy leads to increased male levels and testosterone treatment leads to reduced female levels. However, a number of treatments which also lead to reduced testosterone levels do not lead to increased porphyrins and may, in fact, prevent the rise which would normally follow orchidectomy. One of these antiporphyrinogenic treatments is exposure to short day photoperiods. Thus, the sexual differences in porphyrin, levels in Syrian hamsters are maintained, despite seasonal fluctuations in hormone levels. This suggests that this dimorphism is important for the function of the gland.

The Harderian gland: perspectives.

This is the three-hundred and second anniversary of the first description of Harderian glands by Johann Jakob Harder. Despite more than three centuries of study, many features of these glands, including their definition and function, are not yet established to everyone's satisfaction. Some topics of Harderian biology will be reviewed. Morphology, ontogeny: Mammalian Harderian glands secrete largely by exocytosis, which is unusual in a lipid-secreting exocrine gland. Polytubular complexes are features of male hamster glands; their significance is unknown. Porphyrins: High levels of porphyrin in rodent Harderian glands have made this an attractive organ for research on the control of porphyrin synthesis. Attempts to use it as a model of human porphyria, however, have been disappointing. We do not know the function of Harderian porphyrin. The golden (hamster) age: Syrian (golden) hamster Harderian glands show marked sexual differences, including porphyrin levels. This has made them a very useful experimental animal for endocrine studies. The pineal connection: Rodent Harderian glands contain melatonin. Pinealologists often also study Harderian glands, and Harderianologists also often study the pineal. This relationship has contributed valuable insights to our knowledge of both systems. Lipids: Rodent Harderian glands are about 20% lipid by wet weight, and the main secretory product is lipid. The main lipid in many animals is 1-alkyl-2, 3-diacylglycerol. Harderian gland lipid is extensively studied for insights into lipid biochemistry; less has been done on understanding the function of lipids in the physiology of the glands. Behavior: Lipids may function as vehicles for pheromone secretion. In addition, the possible use of Harderian secretion during cold temperatures by gerbils has been noted. Immunology: Bird Harderian glands are probably lymphoid organs. This does not seem to be true of mammals, though the female Syrian hamster shows large numbers of mast cells. Harderian glands of amphibians and reptiles: Research on nonmammalian Harderian glands has been limited, though important insights continue to emerge from these studies.

Androgenic control of 1-alkyl-2,3-diacylglycerol in the harderian gland of the golden hamster, Mesocricetus auratus.

Harderian glands of golden hamsters produce a copious lipid secretion, most of which is in the form of 1-alkyl-2,3-diacylglycerol (ADG). Sexual differences are seen in the composition of golden hamster ADG and in the morphology of secretory lipid droplet. ADGs from females contained abundant iso- and anteiso-branched chain alkyl groups and fatty acids [Seyama, Y., Otsuka, H., Ohashi, K., Vivien-Roels, B., and Pevet, P. (1995) J. Biochem. 117, 661-670]. Female hamsters were either untreated or given subcutaneous testosterone pellets. Treatment of females with testosterone led to the disappearance of such branched chain alkyl groups and fatty acids. Intact males had ADGs with entirely saturated straight chain alkyl groups and fatty acids. Castration led to the appearance of iso- and anteiso-branched chain alkyl groups and fatty acids. These observations suggested that the production of branched chain fatty acids in the Harderian gland of golden hamster is inhibited by testosterone at the step of isovaleryl-CoA dehydrogenase and 2-methyl branched-chain acyl-CoA dehydrogenase

Control of secretory lipid droplets in the harderian gland by testosterone and the photoperiod: comparison of two species of hamsters.

Harderian glands of mammals secrete lipid. They are markedly sexually dimorphic in Syrian (golden) hamsters (Mesocricetus auratus): female glands consist almost entirely of one cell type (type I) with small lipid droplets, whereas glands of males have both type I and type II cells, with large lipid droplets. Siberian (Djungarian) hamsters (Phodopus sungorus) have sexually monomorphic Harderian glands, with both type I and type II cells. We used a morphometric technique to quantify the proportions of small (type 1) and large (type 2) lipid droplets in these two species, in relation to the presence or absence of testosterone and to variations in the photoperiod. In Syrian hamsters, orchidectomy led to a marked increase in the proportion of type 1 lipid droplets in males kept in long (but not short) day photoperiods. In contrast, treatment of females with testosterone led to an increase in type 2 lipid droplets. Short-day photoperiods in both sexes led to an increase in the proportion of type 2 lipid droplets and this was prevented by pinealectomy. In Siberian hamsters, on the other hand, castration or short photoperiods had no effect on Harderian gland morphology in either sex. These results suggest that some property of type 2 lipid droplets is important to Syrian hamsters during the autumn and winter. Syrian hamsters have a dimorphic Harderian gland and testosterone maintains the basic sexual dimorphism during the long days of spring and summer; a pineal-mediated mechanism, perhaps the drop in serum prolactin levels, leads to an increase in type 2 lipid droplets with the short days of autumn and winter.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgenic control of porphyrin in the Harderian glands of the male Syrian hamster is modulated by the photoperiod, which suggests that the sexual differences in porphyrin concentrations in this gland are important functionally.

BACKGROUND: The porphyrin concentrations of the Harderian glands of Syrian hamsters show marked sexual differences, with male levels being much lower than those of females. Porphyrinogenesis is inhibited by androgens, so orchidectomy leads to elevated male porphyrin concentrations; however, a number of other procedures (some of which also lower androgen levels) prevents this. We studied the effects of short-day photoperiods and melatonin on Harderian porphyrin concentrations. METHODS: Intact, castrated, or pinealectomized hamsters of both sexes were exposed to long-day or short-day photoperiods. Intact or castrated hamsters were given melatonin injections in the morning or the afternoon, or were given beeswax pellets containing melatonin. After a variable period, Harderian glands were dissected and porphyrins were measured. RESULTS: Prolonged short-day exposure (13 weeks) led to increased Harderian porphyrin concentrations and this rise was prevented by pinealectomy. The rise in Harderian porphyrins following short-day exposure was small, compared with that following castration. Short-day photoperiods also prevented the rise in porphyrin levels associated with castration and this effect was prevented by removal of the pineal. Melatonin injections, whether given in the morning or in the afternoon, had no effect on Harderian porphyrin concentration of castrated male hamsters. Continuous release melatonin pellets reduced the postcastrational rise in porphyrin levels in one experiment, while having no effect in another. In female hamsters, neither short photoperiods nor melatonin pellets influenced Harderian porphyrin concentrations. CONCLUSIONS: These results suggested that a factor from the pineal gland helps maintain the low levels of porphyrin which are characteristic of male Harderian glands, despite the decrease in androgen levels which typically results from exposure to short days. Morning and afternoon injections of melatonin and continuous release melatonin pellets failed to resolve the question of whether this pineal factor is melatonin. Our results demonstrated that low male and high female porphyrin levels are maintained in Syrian hamsters, despite seasonal variations in the hormonal milieu, suggesting that these sexual differences are important for the (still unestablished) function of the Harderian glands in this species.

Photoperiod and the pineal gland regulate the male phenotype of the Harderian glands of male Syrian hamsters after androgen withdrawal.

The Harderian glands of Syrian hamsters exhibit a marked sexual dimorphism in cell types and porphyrin production. The glands of male hamsters have two secretory cell types (Type I and II) while the glands of females consist of a single secretory cell type (female Type I) and large intraluminal deposits of porphyrins. Besides androgens, there is evidence that the pineal gland, through the secretion of melatonin, contributes to the maintenance of the "male" and "female" phenotypes. In this study, we investigated the effects of castration, short photoperiods, and pinealectomy on the distribution of secretory cells and porphyrin deposits in the Harderian glands of male Syrian hamsters. Two groups of animals were maintained in long days (14 hr light/day). Hamsters in one group were left intact and those in the other were castrated. Another three groups were maintained in short days (8 hr light/day); these animals were either left intact, castrated, or both castrated and pinealectomized. The duration of the experiment was 5 weeks. Castration of long photoperiod-exposed animals resulted in a significant drop in the number of Type II cells and a large increase in the porphyrin deposits (P < 0.01). However, castrated animals exposed to short photoperiod showed a significant smaller change in both parameters compared with those exposed to long days (P < 0.05). Pinealectomy prevented the effects of short days in castrated animals. No significant changes were observed in the relative number of mitotic figures or in the number of cell nuclei, indicating that the changes observed were due in part to a transformation of Type II into Type I cells. In a second experiment, male hamsters were injected daily either with 25 micrograms of melatonin late in the afternoon or with the saline for 8 weeks. The administration of melatonin resulted in a significant (P < 0.05) increase in the percentage of Type II cells. We conclude that when circulating androgens are very low or absent, pineal melatonin maintains the male phenotype in the Syrian hamster Harderian gland.

Circadian rhythms in reproductive and thyroid hormones in gonadally regressed male hamsters exposed to natural autumn photoperiod and temperature conditions.

Two groups of young adult male Syrian hamsters were kept in a vivarium at 22 degrees C and a light:dark cycle of 14.5:9.5 h (lights on 06.30 h; indoor) or in a naturally decreasing photoperiod and fluctuating ambient temperature conditions (outdoor) from October 1 (day length 11 h 50 min) to November 30 (day length 10 h 12 min). Representative animals from each group were killed at 3-hour intervals with additional time points near the onset of light. Weights of the paired gonads and accessory organs revealed that all of the animals kept outdoors and none of those kept indoors underwent reproductive regression. Significant circadian rhythms were observed in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3) and testosterone in indoor and outdoor-housed hamsters. The 24-hour acrophase in serum LH, TSH, T4 and T3 occurred between 13.00 and 16.00 h, while that of serum testosterone and PRL occurred between 18.00 and 20.00 h in indoor hamsters. Hormonal variables in which there was a significant alteration in the 24-hour acrophase of outdoor animals relative to that in the indoor animals included pituitary PRL and serum testosterone, PRL, FSH and TSH. Hamsters housed indoors had a significant rhythm in brown adipose tissue type-II 5'-deiodinase activity, but no rhythm was evident in this tissue in outdoor animals. The natural autumnal conditions depressed serum LH and testosterone around the clock, though the depression of serum FSH relative to indoor hamster values was best seen between 09.00 and 21.00 h and that for PRL between 15.00 and 24.00 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgen receptor in the harderian glands of the golden hamster: characterization and the effects of androgen deprivation, the pituitary, and gender.

The harderian glands of the golden hamster were found, by a competitive binding assay using [3H]mibolerone as the ligand, to have a high affinity androgen receptor. In intact male hamsters, this receptor was present in both cytosolic and nuclear KCl-extractable fractions. Castration or hypophysectomy led to 3- to 5-fold increases in the concentrations of cytosolic receptor with decreased dissociation constants. Hypophysectomy with maintenance of prolactin levels (by removal of pituitaries and their implantation either in the sella turcica or under the kidney capsule) had no effect on androgen receptor binding, compared to hypophysectomy alone. Female hamsters had androgen receptor levels which were 2 to 4 times higher than those of intact males. Hypophysectomy led to elevated receptor binding in ovariectomized female hamsters and this rise was prevented by maintaining prolactin levels. Binding of [3H]mibolerone in male glands was effectively inhibited by 5 alpha-dihydrotestosterone, whereas the parent molecule, testosterone, required approximately a 10-fold greater molar excess to achieve the same amount of inhibition. Estradiol and progesterone were relatively poor inhibitors of the observed binding of [3H]mibolerone, while dexamethasone was ineffective. Sucrose gradient studies indicated that the harderian androgen receptor migrated to the 8S region, as expected for this receptor in molybdate-containing gradients. These results indicate that the androgen receptor in the hamster harderian gland is a 5 alpha-dihydrotestosterone receptor.

Insulin-like growth factor-1 in Syrian hamsters: interactions of photoperiod, gonadal steroids, pinealectomy, and continuous melatonin treatment.

Four experiments in Syrian hamsters examined the role and possible interaction of photoperiod, gonadal steroids, and the pineal on circulating levels of insulin-like growth factor-1 (IGF-1). In the first experiment, female hamsters were exposed to long photoperiod (LP; 14:10 LD) or short photoperiod (SP; 8:16 LD); an additional group of SP-exposed females was pinealectomized (PX). SP induced a significant depression in IGF-1 concentrations which PX partially prevented. In Experiment 2, two groups (control and castrate [CX]) of adult male hamsters were kept in LP, and three groups (intact, CX, and CX+PX) of hamsters were kept in SP for five weeks. The four groups of animals that were CX and/or maintained in SP had approximately the same mean level of IGF-1, and all four groups were significantly (P < 0.001) higher than the LP-control hamsters. In Experiment 3, four groups (intact controls, CX, CX+melatonin pellet [MEL PEL], and MEL PEL only) were kept in LP. Melatonin pellets (1 mg melatonin/24 mg beeswax/every two weeks) were implanted sc twice during the experiment. Castration induced a rise (P < 0.001) in IGF-1 levels, and this was not prevented by MEL PEL. In Experiment 4, testosterone and dihydrotestosterone pellets implanted in LP-exposed CX males prevented the CX-induced rise in IGF-1; testosterone implants also reduced IGF-1 levels in CX males treated with progesterone. In conclusion, SP treatment depresses IGF-1 in female hamsters and raises it in males. These results substantiate previous studies in other models of gonadal steroid deficient animals. They lend further credence to the hypothesis that there is a sexual dimorphism in circulating IGF-1 concentrations in the Syrian hamster that may be at least partially related to the presence of gonadal steroids.

Pineal acid phosphatase activity in Syrian hamsters: sex differences and effects of castration and androgen replacement therapy.

Pineal acid phosphatase (ACP) activity was examined in seven experiments involving young intact or castrated male and female Syrian hamsters. Nine-week old female hamsters had a 3-fold (p < 0.001) higher ACP activity in their pineal glands than did males. After three weeks of castration, a significant increase (p < 0.001) in ACP activity occurred in castrated male pineal glands. In males, pellets with 5 alpha-dihydrotestosterone (p < 0.01) but not testosterone or progesterone suppressed pineal ACP activity. In females, no changes in pineal ACP activity were noted due to the estrous cycle. Pineal ACP activity was not affected by testosterone, dihydrotestosterone or androstenedione pellets in intact females or by testosterone pellets in ovariectomized animals.

Porphyrin metabolism in the harderian glands of Syrian hamsters: in vivo regulation by testicular hormones, lighting conditions, pineal gland, and pituitary hormones.

The porphyrin concentration in the harderian glands of male hamsters subjected to several endocrine manipulations was studied. Prolonged bilateral gonadectomy resulted in a marked increase in harderian porphyrin concentration. This change was not prevented by either pinealectomy or by constant white light exposure. Castrated hamsters exposed to constant red light showed higher porphyrin concentrations than castrated hamsters kept under white light. Among several hormones studied, serum luteinizing hormone and thyroid-stimulating hormone levels were unexpectedly higher in the constant red light exposed group than in the other groups. In order to test whether luteinizing hormone was involved in the postcastrational rise in harderian porphyrins, we administered a potent luteinizing hormone-releasing hormone (LHRH) agonist. The chronic administration of the LHRH agonist resulted in a decrease in serum luteinizing hormone (because it desensitized the LHRH receptors on the gonadotropes) and, consequently, in serum testosterone levels. However, no rise in harderian porphyrin was observed. It is concluded that the absence of testicular hormones might not be the triggering factor involved in harderian porphyrogenesis.

Hypophysectomy prevents the castration-induced increase in porphyrin concentrations in the harderian glands of the male golden hamster: a possible role for prolactin.

The Harderian glands of golden hamsters contain high concentrations of porphyrin pigments, with female hamsters having considerably higher porphyrin concentrations than males. Castration of male hamsters leads to a rapid increase in porphyrin concentrations; testosterone treatment of females has the opposite effect, suggesting a central role for androgens in inhibiting the realization of high porphyrin concentrations by this organ. Previous studies in our laboratories have shown, however, that administration of a dopamine agonist to castrated hamsters prevents the normal increase in Harderian porphyrins from occurring. This suggests that prolactin is necessary for low androgen levels to lead to maximal increases in Harderian porphyrin concentrations. The present study tested the hypothesis that prolactin is involved in the control of Harderian porphyrin levels in the golden hamster. Although hypophysectomy of male hamsters reduced serum testosterone to levels in castrated hamsters, the resultant increase in Harderian porphyrin concentrations was much less than that seen after a similar period of castration. Furthermore, combining the two procedures (castration and hypophysectomy) also led to a blunted increase in Harderian porphyrin, suggesting that a pituitary hormone is necessary for low testosterone levels to lead to increased porphyrins. Evidence that this pituitary hormone is prolactin comes from the observations that eliminating all pituitary hormones except prolactin, by severing the connection of the pituitary with the hypothalamus or transplanting the pituitary to a distant site (beneath the kidney capsule) led to greatly augmented Harderian porphyrin levels, in intact or castrated male hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Inhibition of 5 alpha-reductase does not simulate the effects of androgen deprivation on porphyrin metabolism by harderian glands from the male Syrian hamster.

As 5 alpha-reductase is involved in the metabolism of indolamines in the Harderian glands of Syrian hamsters, we have compared the effects of androgen deprivation and the administration of the potent 5 alpha-reductase inhibitor N,N-diethyl-4-methoxy-3-oxo-4-aza-5-androstene-17-carboxamida on Harderian porphyrin metabolism. Ten days after castration, porphyrin levels had increased to 40 times the values of intact hamsters. However, the inhibition of 5 alpha-reductase, which resulted in a significant decrease in the weight of accessory sex glands, did not modify porphyrin concentrations within the Harderian glands. It is concluded that, contrary to the situation for indolamine metabolism, testosterone per se is the main androgen involved in the sexual differences observed in Harderian porphyrin metabolism.

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.

Indole and porphyrin content of the Syrian hamster harderian glands during the proestrous and estrous phases of the estrous cycle.

Porphyrin and indole metabolism was studied in the Harderian glands of Syrian hamsters during the proestrous and estrous stages of the estrous cycle. Porphyrins remained unaltered during these stages, but levels of different indoles (5-hydroxytryptophan, 5-hydroxytryptamine, N-acetyl-5-hydroxytryptamine, and 5-hydroxyindole acetic acid) exhibited pronounced changes during the dark:light period in both proestrous and estrous. There was a strong parallelism between 5-hydroxytryptamine, N-acetyl-5-hydroxytryptamine and 5-hydroxyindole acetic acid levels. Hydroxytryptophan rhythms appeared slightly shifted from those of the other indoles. Immunoreactive melatonin present in the Harderian glands did not show a significant day-night change during the stages studied.

N-acetyltransferase activity in the Harderian glands of the Syrian hamster, Mesocricetus auratus, is regulated by androgens and by hormones of the pituitary-thyroid axis.

This study tested the hypothesis that activity of the enzyme N-acetyltransferase (NAT) in the Harderian gland of the Syrian hamster is regulated both by androgens and by hormones of the pituitary-thyroid axis. To test the effects of castration and hypothyroidism, intact or castrated male hamsters were given either tap water or methimazole in their drinking water for 3 weeks. Methimazole suppresses iodination of thyroglobulin, thereby decreasing circulating levels of thyroid hormones and increasing TSH levels. Hypothyroidism or castration caused elevated or depressed Harderian gland NAT activities respectively, compared with euthyroid controls. When castration and hypothyroidism were combined, the animals exhibited high NAT activity compared with castrated euthyroid males. To test the effects of castration and hyperthyroidism, male hamsters were given daily injections of thyroxine (T4) or diluent and were either castrated or left intact for 4 weeks. Intact animals given T4 had depressed Harderian NAT activity; serum thyroid hormone levels were elevated and TSH levels were depressed compared with those of intact controls. Castrated animals had depressed NAT activity below that of intact controls; serum thyroid hormone levels were normal but TSH levels were depressed. Castrated animals given T4 injections had NAT activity similar to that of euthyroid castrated hamsters; thyroid hormone levels were elevated but TSH levels were similar to those seen in euthyroid castrated hamsters. In another experiment, both T4 and tri-iodothyronine (T3) were equally effective in decreasing NAT activity in intact males. To determine the effects of the removal of pituitary influences, male hamsters were hypophysectomized. NAT activity in the Harderian glands of these animals was reduced compared with intact controls.(ABSTRACT TRUNCATED AT 250 WORDS)