Abstract
A mathematical model for LH levels in the recently-castrated rat is presented. It is simply based on an increase of both production and release of pituitary LH after castration. Solutions of the model equations are shown to correlate well with data in the adult rat when the release rate-constant is taken as β = 0·4 ± 0·15 day−1 and the production-increase rate-constant is taken as γ = 0·07 ± 0·03 μg (LH)/mg (pit.)/day2. The available data do not permit any sex difference to be determined in these two rate-constants. The correlation also does not depend sensitively on variations in their numerical values. A minimum LH storage level in the pituitary, LHp0, is an integral postulate of the model; a value of 0·25 μg/mg being estimated from data in the normal estrous cycle. With this model for post-castration behavior, the greater initial increase of serum LH in the male than in the female can be explained as primarily due to the larger pituitary LH concentration in the male at the time of castration. Since the analysis makes no attempt to relate post-castration behavior to events in the estrous cycle, the female at proestrous is excluded from consideration. When analyzing serum LH data measured in ng(LH)/ml (serum) it is important to note the difference in LH distribution volume between males and females of different body weights. The ratio of pituitary weight to distribution volume is shown to be an important scaling factor for correlating serum hormone data.
Published Version
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