Daily Rhythms of Serum Luteinizing Hormone in the Immature Hamster are Estradiol-Dependent1

Donham, Richard S.; Posern, F Von; Stetson, Milton H.

doi:10.1095/biolreprod36.4.864

Cited by 2 publications

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“…In this regard, the daily afternoon surges are as effective in stimu¬ lating the endocrine development of the ovaries as are constant high levels of LH and hence are a functionally more efficient means of achieving the increasing concentrations characteristic of the peripubertal phase. The daily surges in the female hamster, which develop by 16 days of age and persist until puberty, almost certainly serve the same function (Donham et al, 1984(Donham et al, , 1986(Donham et al, , 1987 and, in addition, stimulate development of the gametogenic ovary.…”

Section: Discussionmentioning

confidence: 99%

Daily rhythms of pituitary--ovarian function in the immature hamster are independent of adrenal and pineal influence

Donham

Rollag²,

Stetson³

1988

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In female hamsters, the daily rhythm of LH appeared on the 15th or 16th day after birth with a peak occurring at about 16:00 h (14L:10D, lights on 06:00 h). Progesterone concentrations increased and became rhythmic a few days later. In serum samples collected at 14, 16, 18, 20, 25, 30, 40 and 60-62 days of age between 13:00 and 23:00 h, significant rhythms of serum cortisol and corticosterone concentrations were not detected before 25 days of age; furthermore, the phase of the rhythms did not stabilize to the adult pattern until about 40 days of age. As in the adult, significant rhythms were present in both sexes and the levels of cortisol were greater than those of corticosterone. Injection of pig ACTH (50 i.u./kg body wt, i.p.) significantly increased serum cortisol by 10 days of age, but corticosterone did not respond until 25 days of age. Thus, for cortisol at least, the appearance of 24-h rhythms in the serum is probably not dependent on the ability of the adrenal to respond to ACTH. Ovariectomy had no effect on the late afternoon surge of serum cortisol; similarly, adrenalectomy of immature females did not abolish the surge of LH. Ovariectomy did not alter the daily rhythm of pineal melatonin content and pinealectomy had no effect on the daily afternoon surge of LH. These results demonstrate functional independence of circadian rhythms in the pituitary-gonadal axis and the pituitary-adrenal axis of the immature hamster and also independence of daily rhythms of pineal melatonin and pituitary release of LH.

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Section: Discussionmentioning

confidence: 99%