Reaction of Anterior Pituitaries of Immature Female Rats to Injections of Various Amounts of Oestrin. ∗

Abstract

It is well established that injection of oestrin in normal female rats induces changes in the anterior hypophysis comparable to those of pregnancy and that such injections in castrated female rats prevent typical castration changes. Daily injection of large amounts of oestrin into normal female rats for 10 days results in a marked but variable weight increase in the pituitaries. The basophiles are markedly degranulated and reduced in relative percentage. The eosinophils also present loss of granules and a variable reduction in relative percentage. The chromophobes are greatly increased in relative percentage. 1 In the studies recorded below we have attempted to ascertain more exactly the morphologic and quantitative effects of large and small daily injection of oestrin for periods of 5 and 10 days on the various cell types of the anterior pituitaries of immature female rats. We wished to determine if the amounts of oestrin necessary to cause changes in one cell type would induce changes in the other types. Female rats, 21 to 23 days old were used. At autopsy, body, ovary and pituitary weights were obtained. Serial sections of all pituitaries were cut. Five representative sections from each were studied; differential cell counts were made on each; the number of mitoses were also counted.

In the first series, 9 rats received daily injection of 10 units of oestrin† for 5 days; a second group of 8 littermates received daily injection of 200 units for the same period. Eleven littermate controls were available. In the rats receiving, 10 units daily the pituitaries were increased in weight to a mean of 3.5 mg.; the mean in the controls was 2.6 mg. The basophiles of the injected rats were moderately degranulated; the result was a decrease in the relative levels of the granular basophiles to a mean of 2.8% while this mean in the controls was 8.3%. A few of the eosinophiles in the injected rats were swollen and showed loss of granules. The relative percentages of eosinophiles were not decreased when compared with the controls. This may possibly be explained by the fact that in the injected rats the number of mitoses found in the eosinophiles was much greater than in the controls; the mean number per section in the injected rats was 14.7 while in the controls it was only 3.2. The mean number of mitoses per section in the chromophobes was also increased; in the injected rats it was 18.4 while in the controls it was 7.7.