Regression Rate of Vascular Effects Induced by Pregnancy and by Norethynodrel-Mestranol

Abstract

Based on results in a previous study showing specific vascular changes as the result of pregnancy and administration of norethynodrel-mestranal in the rabbit an attempt was made to determine how long these changes persist after the conclusion of pregnancy and after withdrawal of norethynodrel-mestranol. 8 pregnant rabbits and 8 norethynodrel-mestranol-treated rabbits were studied. The pregnant rabbits were allowed to deliver at term and 1 was sacrificed every second day from Postpartum Day 1-15. Histological preparations were made. Since normal findings were noted in all cases at 15 days postpartum 3 additional rabbits were sacrificed on different days. In the norethynodrel-mestranol-treated group each animal was treated with .2 mg intramuscularly daily for 6 days and then sacrificed every second day from Day1-15 after conclusion of treatment. 3 additional animals were sacrificed. It was concluded that in the rabbit the vascular effects of pregnancy and of norethynodrel-mestranol disappear at variable rates after the withdrawal of the stimulus. Reticular fragmentation persists until about 15 days after pregnancy conclusion and for 10 days after norethynodrel-mestranol therapy cessation. Acid mucopolysaccharides return to normal immediately in both instances. Muscle changes and elastic tissue changes are virtually normal within 10 days and completely normal within 15 days for both groups.