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  • Title: Effects of daylength on androgen metabolism and pulsatile luteinizing hormone secretion in male golden hamsters.
    Author: Krey LC, Ronchi E, Bittman EL.
    Journal: Neuroendocrinology; 1989 Nov; 50(5):533-42. PubMed ID: 2514394.
    Abstract:
    In an effort to understand the potential neuroendocrine mechanisms underlying photoperiodic control of fertility in seasonally breeding species, we monitored the intracellular processing and nuclear uptake of [1 alpha, 2 alpha-3H]testosterone (3H-T) within the brain-pituitary complex as well as the patterns of episodic luteinizing hormone (LH) secretion in male golden hamsters exposed to long day (14 h light:10 h dark) and short day (10 h light:14 h dark) photoperiods. Target tissue specific patterns of nuclear 3H-androgens and estrogens were observed in castrated, T-replaced hamsters exposed to long and short days for 7 weeks or longer. Significantly, 3H-T metabolism or receptor-mediated nuclear uptake in the hamsters in short days was not influenced in any manner that would explain their increased responsiveness to androgen feedback suppression of LH release. Comparable patterns of episodic LH secretion were observed in acutely catheterized hamsters castrated for 7 weeks prior to exposure to 8 weeks of long or short days. Similar patterns were also observed in animals maintained in long days and castrated 1 or 2 weeks prior to blood collection. However, such a pattern was not seen in acutely castrated hamsters maintained in the short-day photoperiod. The data suggest that steroid-independent mechanisms play an important role in suppressing gonadotropin release in short days in this species. However, such mechanisms appear to be most effective when the animals are or have recently been exposed to circulating androgens.
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