Seasonal relationship between pineal hydroxyindole-O-methyltransferase (HIOMT) activity and reproductive status in the pony.
Abstract: Pony pineal glands and female reproductive tracts were collected monthly for 1 year from
a local slaughterhouse. Pineal gland weights did not change significantly throughout the year.
Pineal gland tissue homogenates were assayed for hydroxyindole-O-methyltransferase
(HIOMT) activity with N-acetylserotonin as the primary substrate. The greatest HIOMT
activity was obtained with N-acetylserotonin as substrate. but three other related S-OH
indole substrates (5-hydroxytryptophol, serotonin. and 5-hydroxy-2-methylindole) were also
methylated. HIOMT activity with all substrates was highest during the late fall and winter
(November-February) and lowest during the spring, summer, and early fall (AprilOctober). Percentage of mares ovulatory was inversely related to pineal HIOMT activity, except that there was a I- to 2-month lag phase. These findings are consistent with a
hypothesized antigonadal activity of both melatonin and the pineal in mammals.
Publication Date: 1979-05-01 PubMed ID: 467970DOI: 10.1016/0016-6480(79)90087-xGoogle Scholar: Lookup
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- Journal Article
Summary
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The research article examines the correlation between the activity of the enzyme hydroxyindole-O-methyltransferase (HIOMT) in the pineal gland of ponies and their reproductive behavior through the different seasons of the year.
Research Context and Methodology
- The study aims to explore the seasonal relationship between the activity of an enzyme in the pineal gland, hydroxyindole-O-methyltransferase (HIOMT), and its impact on the reproductive status of ponies.
- To carry out the study, the pineal glands, located in the brain and involved in regulating the body’s internal clock, and female reproductive tracts of ponies were gathered every month for a year from a local slaughterhouse.
- The researchers then created tissue homogenates from the obtained pineal glands and used these to study the activity of HIOMT. N-acetylserotonin was primarily used as the substrate, though three other related S-OH indole substrates were also analyzed.
Research Findings
- It was observed that the pineal gland weights remained stable throughout the year, suggesting that changes in HIOMT activity are not due to fluctuations in gland size.
- HIOMT activity, with all substrates, was found to be highest during late fall and winter (November to February) and lowest during spring, summer, and early fall (April to October).
- The research unveiled a noteworthy pattern: the percentage of mares that were ovulating was inversely related to pineal HIOMT activity, meaning that when this enzyme’s activity was high, fewer mares were ovulating and vice versa. This correlation was consistent, albeit with a lag phase of one to two months.
Research Implications
- The results demonstrate a potential antigonadal activity of melatonin and the pineal gland in mammals, as higher activity of the HIOMT enzyme, related to melatonin synthesis, correlates with reduced ovulation in mares.
- This research could provide a hormonal explanation for the seasonal variations in the reproductive behavior of ponies and potentially other mammals.
- The findings contribute to the broader scientific understanding of the influence of pineal gland activity on biological rhythms and reproductive schedules in mammals.
Cite This Article
APA
Wesson JA, Orr EL, Quay WB, Ginther OJ.
(1979).
Seasonal relationship between pineal hydroxyindole-O-methyltransferase (HIOMT) activity and reproductive status in the pony.
Gen Comp Endocrinol, 38(1), 46-52.
https://doi.org/10.1016/0016-6480(79)90087-x Publication
Researcher Affiliations
MeSH Terms
- Acetylserotonin O-Methyltransferase / physiology
- Amines / analysis
- Animals
- Female
- Horses / physiology
- Indoles / analysis
- Light
- Male
- Melatonin / biosynthesis
- Methyltransferases / physiology
- Ovulation / drug effects
- Peptides / analysis
- Pineal Gland / analysis
- Pineal Gland / enzymology
- Reproduction
- Seasons
- Sex Factors
Citations
This article has been cited 2 times.- Balemans MG, Bary FA, Legerstee WC, Van Benthem J. Seasonal variations in HIOMT activity during the night in the pineal gland of 21 day old male Wistar rats. J Neural Transm 1980;49(1-2):107-16.
- Balemans MG, Pévet P, van Benthem J, Haldar-Misra C, Smith I, Hendriks H. Day/night rhythmicity in the methylating capacities for different 5-hydroxyindoles in the pineal, the retina and the Harderian gland of the golden hamster (Mesocricetus auratus) during the annual seasons. J Neural Transm 1983;56(1):53-72.
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