Historical control data on reproductive abilities and incidences of spontaneous fetal malformations in Wistar Hannover GALAS rats

Abstract

Wistar Hannover rats, which have recently been introduced into Japan, are expected to be used in reproductive and developmental toxicity studies, yet the accumulation of background data is insufficient. This paper describes our historical data on the reproductive ability of this strain of rat. Three lots of sexually matured females (40 each) were received from CLEA JAPAN, Inc. with males of the same strain (30 or 36 each) and mated. A total of 47 dams were killed on gestation day 20 to examine their fetuses. The remaining 71 pregnant females were allowed to deliver spontaneously and observed for common reproductive parameters. The mating and fertility indices of females were both 99.2%. Overall mean numbers of implants and live fetuses at cesarean sectioning were 12.5 and 11.5, respectively. Fetal resorptions and deaths occurred at an incidence of 8.6%. Morphological examinations of fetuses revealed low incidences of spontaneous malformations (each one case of double aortic arch and absent cervical vertebral arch) and a variety of common variations. The followings are overall means of major reproductive parameters obtained from females with live birth: no. of implants, 12.5; no. of pups delivered, 11.8; viability index of pups at birth, 99.8%; and days of age at sexual maturation (vaginal opening and preputial separation), 30.3 and 42.8, respectively. Our present observations confirmed a minimal deviation among 3 lots of animals in terms of reproductive abilities. These results suggest that this strain of rat can be used in reproductive and developmental toxicity studies, although the sensitivity to toxicants remains to be elucidated.

A Simple Breeding Protocol for the Procurement of Accurately Staged Rat Donor Embryos for Neural Transplantation

“…2 and 3). Similarly, based on reports that estrus tends to last for approximately 12 h (25), we reasoned imately 4 days (1,12,21,25) and that estrus cycles of cage mates may not necessarily be synchronized, we hythat some females may have already passed estrus by the time they encounter the male. So we tried to pair pothesized that at any given time one in four females may be in estrus and ready for mating.…”

“…Holehan and Using the vaginal lavage method has proven to be the most effective and easiest way to determine estrus in Merry (7) report that younger rats have larger litters and that maximum fertility drops to 30% in intermittently rats (1,10,12,13,21). Using two independent raters, we were able to establish a 100% concordance in the detecbred females over 10 months of age.…”

“…Estrus stages were identified by two blind raters. described previously (1,25). With animals living in a normal 12-h light/dark cycle room, eligible females in While discerning metestrus from diestrus was at chance level, the experimenters agreed on proestrus and estrus estrus were established by lavage in the morning of the intended pairing.…”

“…Here estrus was determined using vaginal lavage (1,4,7,12,21); pregnancy was confirmed by their own in-house breeding employ a variety of methods in the routine production of pregnant rat dams. For anesthetization of the dam and palpation of the abdomen 11 or 12 days postmating (6,16).…”

A Two-Generation Reproductive Toxicity Study of 2,4-Dichlorophenol in Rats

“…Male and female SPF Wistar Hannover rats (BrlHan: WIST@Jcl (GALAS) rats; CLEA JAPAN, Inc.) were used in this study because of their excellent reproductive status (Aoyama et al, 2002). They were reared in a barrier-sustained animal room under controlled conditions of temperature (24±2°C), relative humidity (55±15%), ventilation (at least 10 times/hr, all-fresh-air system), and 12-hr light/dark cycles throughout the study.…”