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Attenuated nocturnal rise in pineal and serum melatonin in a genetically cardiomyopathic Syrian hamster with a deficient calcium pump
Author(s) -
Reiter Russel J.,
White Ted,
Lerchl Alexander,
Stokkan KarlArne,
Rodriguez Carmen
Publication year - 1991
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1991.tb00472.x
Subject(s) - melatonin , hamster , medicine , endocrinology , calcium , nocturnal , syrian hamsters , mesocricetus , biology
Day and nighttime melatonin production in the pineal gland was compared in normal and cardiomyopathic (polydystrophic) adult male Syrian hamsters. These strains of hamsters were selected for comparison because the cardiomyopathetic hamster displays a deficient transmembrane Ca 2+ ‐pump in a number of tissues, and intracellular Ca 2+ concentrations ([Ca 2+ ]i) play a central role in the nocturnal increase in pineal melatonin synthesis. Daytime levels of all constituents measured, i.e., pineal N‐acetyltransferase (NAT) activity, pineal and serum melatonin levels, and pineal 5‐hydroxytryptophan (5‐HTP), serotonin, and 5‐hydroxyindole acetic acid (5‐HIAA) contents, were comparable in control and dystrophic hamsters. In contrast, the nighttime rises in pineal NAT activity and pineal and serum melatonin levels were significantly attenuated in the dystrophic hamsters. By comparison, the pineal contents of 5‐HTP, serotonin, and 5‐HIAA were essentially the same in both groups of hamsters with both pineal serotonin and 5‐HIAA values exhibiting the usual nighttime drop. It is presumed that the alterations in nocturnal melatonin production in the pineal gland of the cardiomyopathic hamster may relate to a generalized deficiency in the Ca 2+ ‐pump in pinealocyte plasma membranes, which leads to unusually high [Ca 2+ ]i, causing a depression of NAT activity; this leads to the commensurate decline in pineal and serum melatonin levels. Harderian gland NAT activity and melatonin levels were essentially similar in the two groups of animals, although NAT activity was slightly depressed in the dystrophic hamsters killed during the day. The reduced amounts of intrascapular brown fat in the cardiomyopathic hamster is speculated to be a result of the diminished amount of melatonin produced in these animals.