THE EFFECT OF OVARIECTOMY ON THE ACTIVITY OF CERTAIN ENZYMES IN THE FEMALE RAT HYPOTHALAMUS

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Abstract
Previous work in the rabbit has shown that the activity of certain peptidases in the hypothalamus which inactivate oxytocin, changes with stimuli known to release gonadotrophins, and may be used as an index of gonadotrophin hormone release (Hooper 1966a,b, 1968; Frith & Hooper 1971a,b). Using this approach, a study was made of the activities of similar peptidases in the rat hypothalamus following ovariectomy, a condition known to cause gonadotrophin release. Enzyme activity in the supernatant fraction was found to decrease progressively with time after ovariectomy, until 42 days after operation, thereafter maintaining a level not significantly different from that at 42 days; there was no detectable difference in particulate enzyme activity after ovariectomy. An inverse relationship between supernatant enzyme activity and luteinizing hormone levels is suggested. It is concluded that a similar relationship to that in the rabbit exists between enzyme activity in the rat hypothalamus and the release of luteinizing hormone-releasing factor from the tissue.

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