BREEDING OF MICE WITH SPONTANEOUS ALVEOLAR FORMATION IN THE MAMMARY GLAND. IV. RELATIONSHIP BETWEEN THE LEVEL OF FEEDING AND SPONTANEOUS ALVEOLAR FORMATION.

Abstract

The effect of level of feeding on spontaneous alveolar formation (SAF) was investigated using 35 litters of KP group of mice.Each litter was divided into 2 groups after weaning till 70days of age; free fed group (group F) and restricted fed one (group R).The day of vaginal opening was about 33days after birth in group F and about 51days in group R. On the 70th day, frequency of SAF in group F was about 53%, on the other hand, it was 0% in group R.From the day of 71 th to 90th, some of the SAF positive mice in group F were given restricted food (group FR) and the rest and all of SAF negative mice continued to be fed freely (groups FF and FF'). Some of the group R were fed freely (group RF) and the rest continued to be fed as before (group RR).On the 90th day, half of the mice in group FF' showed positive SAF, frequency of SAF elevated then to 69% in the pooled data of groups FF and FF', and no animals showed positive SAF in group FR. The frequency of SAF in group RF was 44%, while all animals in group RR remained to be negative in SAF.The estrous cycles of some mice in each group were examined throughout the experiment, and it was ascertained that the ovary was active irrespective of feeding conditions. The SAF positive mice had always at least one long cycle.There were some differences among groups in body weights either on the 70th or 90th day and some organ weights on the 90th day. The significance of these findings was discussed.