Quantification and classification of pregnancy wastage in 5-day cyclic young through middle-aged rats.
Fecundity was quantified in 4 to 11-month old rats with regular 5-day cycles. On the day following mating, less than 5% luteinized unruptured follicles occurred in either 4-month old or 11-month old rats; ovulation rate and also fertilization rate were similar in these young and middle-aged rats. At day 19 of pregnancy embryonic and fetal mortalities were quantified. Pregnancy wastage increased gradually with age; it was already significant in 7-month old rats. In rats of 9 months old it was about 30% and in 11-month old rats it was greater than 65%. Pregnancy wastage was mainly due to preimplantation and early-postimplantation mortality. Pregnancy wastage did not decrease when the pre-ovulatory surge of luteinizing hormone (LH) was reinforced and timed, by injection of the LH-releasing hormone analogue Ovalyse at noon on the day of prooestrus. The results corroborate the idea that pregnancy wastage in middle-aged rats with regular cycles is caused by an age-related reduction of the viability of ovulating eggs.
Mattheij
J A
JA
Agricultural University, Department of Human and Animal Physiology, Wageningen, The Netherlands.
Swarts
J J
JJ
D000375:Aging; D000818:Animals; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005298:Fertility; D007986:Luteinizing Hormone / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects; D011247:Pregnancy; D011270:Pregnancy, Animal; D051381:Rats; D011919:Rats, Inbred Strains
D007986:Luteinizing Hormone