Abstract
Summary
Samples of whole blood were collected continuously over 5-min intervals for a period of several hours from individual, nonanesthetized, cannulated, ovariectomized, estrogen-progesterone-treated rats. Plasma LH concentrations were determined by radioimmunoassay of the whole blood after adjustment for hematocrit. The red blood cells influenced the resulting measurements only to the extent to which serum volume was displaced. After the injection of hypothalamic extract, plasma LH concentrations increased 4- to 6-fold within 10 min. Plasma LH concentrations then returned to, but did not fall below, preinjection values. The rate of hormone disappearance from the plasma suggests that, under these conditions, LH release in response to hypothalamic extract is limited to the first few minutes after injection.
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