Volume of the Various Lobes of the Hypophysis During Pregnancy in the Rat

Contrary to the general tendency of the hypophysis, and particularly the anterior lobe, to enlarge during pregnancy in many animals, it appears from the data on 86 albino rats tabulated below, that the organ, as a whole, does not enlarge. If anything, the whole organ is slightly smaller in the normal pregnant animals. No significant difference was found in the relative volume of the various lobes as determined by the paper weight method on serial sections.

All the animals used in these investigations were standard female albino rats reared under uniform conditions in the animal colony of the Department of Anatomy, University of Minnesota.

Group I—Normal non-pregnant controls were specifically chosen litter mates of the animals in Group II. They were all killed at approximately the same body weight of 185 gm.

Group II—Normal pregnant group-Litter mates of Group I were impregnated at about 175 gm. At least one animal was killed on each day of the gestation period, which in a rat is 22 days. Impregnation was done at this age on the assumption that they would have attained an average body weight similar to group I when killed if pregnancy had not been induced.

Group III—Consisted of a group of pregnant animals retained on a diet deficient in the anti-sterility vitamin E, after having passed through one gestation period with a diet deficient in vitamin E.

Group IV—Is a group of pregnant animals which was fed vitamin E after having passed through one gestation period with a diet deficient in vitamin E. This procedure did not apparently modify the relative volume of the lobes of the hypophysis as compared with group III.