Abstract
Adult female rats were exposed to constant light (LL). Initially they ran "normal" estrous cycles; later the vaginal smear pattern became increasingly irregular, and finally a persistent-estrous (PE), anovulatory state developed. Pituitary LH content was measured by the OAAD method on proestrus and estrus of cycles 1-5 in LL, and after 5-30 days of PE. During the early period of LL exposure, while the rats were still cycling, pituitary LH values resembled those obtained in control cyclic rats in an alternating light-dark environment–i.e., high (8.3 μg) on proestrus, and low (4.7 μg) o n estrus when fresh oviductal ova were found–and did not vary significantly from cycles 1-5. LH content of pituitaries from 10-day PE rats was dependent upon the length of time these rats were in LL before PE developed. It was high (11.4 μg) when the PE state evolved during the first 2 months in LL, and low (3.8 μg) when PE occurred following a more prolonged exposure to LL. Pituitary LH in rats showing 5, 15, 20 and 30 days of PE also appeared to be dependent upon the total duration of LL exposure. (Endocrinology77: 1140, 1965)
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