Gerald R. Buzzell

5α-Dihydrotestosterone administration converts indolamine metabolism and porphyrin content of the female syrian hamster harderian gland to the male type

Abstract The effects of ovariectomy and exogenous androgen administration on the indole and porphyrin metabolism of Syrian hamster Harderian glands were studied. Ovariectomy alone had no effect on any of the parameters analyzed. The administration of either testosterone or 5α-dihydrotestosterone increased the activity of N-acetyltransferase in the Harderian glands. However, androgen treatment failed to change the activity of hydroxyindole-O-methyltransferase. Melatonin content of the glands dropped 20 days after treatment with testosterone and 10 days after the administration of 5α-dihydrotestosterone. The porphyrin content of the Harderian glands was dramatically depressed after the administration of either androgen. It is concluded that the Harderian glands of Syrian hamsters are under an androgenic control involving 5α-dihydrotestosterone.

Effects of Short‐Day Photoperiods and of N‐(2,4‐Dinitrophenyl)‐5‐Methoxytryptamine, a Putative Melatonin Antagonist, on Melatonin Synthesis in the Harderian Gland of the Syrian Hamster, Mesocricetus auratus

The Harderian glands of Syrian hamsters contain melatonin and the enzymes N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) which synthesize melatonin from serotonin. Because the Harderian glands share this metabolic pathway with the pineal gland, we examined the effects of short‐day photoperiods, which stimulate pineal‐mediated gonadal regression, and N‐(2,4‐dinitrophenyl)‐5‐methoxytryptamine (ML‐23), which has been described as a melatonin antagonist, on melatonin synthesis in the Harderian glands of the hamster.

Melatonin and porphyrin in the harderian glands of the syrian hamster: Orcadian 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.

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.

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.

Swimming-induced suppression of rat pineal melatonin is prevented by pretreatment with calcium channel blockers (42836)

Abstract Young adult male rats were treated with isoproterenol during the day to induce high levels of pineal N-acetyltransferase (NAT) activity and melatonin. Roughly 2 hr later when pineal NAT activity and melatonin levels were elevated, animals were given either an injection of a calcium channel blocker, i.e., either nifedipine or verapamil, or diluent. The rats were then forced to swim for 10 min in room temperature (22°C) water. Fifteen minutes after swimming onset, pineal glands were collected for measurement of NAT activity and melatonin. Swimming caused a dramatic reduction in pineal melatonin content without influencing NAT activity. Nifedipine substantially and verapamil completely blocked the drop in pineal melatonin levels due to swimming without influencing NAT activity. The results suggest that calcium may be somehow directly or indirectly involved in melatonin release from the rat pineal gland.

Pineal lysosomal enzymes in the Syrian hamster: circadian rhythm and effects of castration or short photoperiod treatment

A circadian rhythm in acid phosphatase and hexosaminidase was found in adult male hamsters exposed to a long photoperiod (14:10 h light/dark [LD]; lights on 06.00 h) and killed at 08.00, 14.00, 20.00, 02.00, 04.00, 05.50 and 0.615 h. Hexosaminidase and beta-glucuronidase activity at 02.00, 04.00 and 05.50 h (values pooled for these times before lights on) were significantly elevated compared to enzyme activity at 06.15 and 08.00 h (pooled values after lights on), suggesting a fall in activity associated with lights on. Hypogonadism was induced in female Syrian hamsters by exposure to a short photoperiod (10:14 h LD) until a majority of them were vaginally acyclic. Pineal lysosomal enzyme activities (acid phosphatase, beta-glucuronidase, hexosaminidase, alpha-arabinosidase and beta-galactosidase) were significantly elevated in short photoperiod-exposed animals compared to animals in 14:10 LD, when measured near the middle of the light phase. In the third experiment, castrated animals were used to determine if lowered androgen levels might also affect pineal lysosomal enzyme activity. The results indicated that light phase beta-glucuronidase, hexosaminidase and beta-glucosidase activities were lower in castrated males compared to their intact controls. In summary, these results demonstrate that (1) lysosomal enzyme activity is present in the Syrian hamster pineal, (2) changes can be observed which suggest involvement of this activity in pineal function and, (3) a circadian rhythm in enzyme activity is present with peak activity occurring during the night. In the short photoperiod and castration experiments, the changes in lysosomal enzyme activity could reflect either a hormonal manipulation or a change in circadian regulation of enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.