Abstract
Summary
Adult rhesus monkeys, spayed for at least eight months before experimentation, were given subcutaneous implants of estrogen or cholesterol. Before treatment, estrogen in these animals ranged from nondetectable levels to 37 pg/ml. After estrogen treatment a physiological level of 75–103 pg/ml was reached; no change in estrogen content was observed in controls given cholesterol. After estrogen administration, plasma LH, which was relatively high in spayed monkeys, declined significantly; cholesterol treatment, however, did not alter the LH contents. An ultrastructural examination of the pituitary in control animals showed that castration cells were present; these hypertrophic gonadotrophs contain numerous large vesicles but few secretory granules. After estrogen treatment, two different forms of gonadotrophs emerged. One, which is thought to represent an intermediate form, had vesicular remnants, a pyknotic nucleus, and an accumulation of large secretory granules. Another, by far the most numerous, contained a large number of secretory granules, showed little or no dilation of ER, and returned to a size comparable to the other parenchymal cells. Our results in spayed rhesus monkeys indicate that both the structure and function of the gonadotrophs are reversed after estrogen treatment.
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